RESULTS AND METHODOLOGY OF THE ENGINEERING ANALYSIS FOR

RESIDENTIAL WATER HEATER EFFICIENCY STANDARDS

Submitted to the

U.S. Department of Energy

Office of Codes and Standards (OCS)

November 2, 1998

EE-RM-97-900 COMMENT 38TT
Addendum

The following changes have been made to the main report:

Page 11 Referenced Appendices A-G

Page 11 Referenced Appendix D

Page 12 Referenced Appendix F

Page 17 Referenced Appendix G

Page 27 Changed text from Table 5 to read "Table 7"

Page 74 Added Table 50a. Cost Table for 40 gallon (150 liter) Gas-Fired Storage Water

Heater - Selected Design Option Combinations

Page 81 Changed text from Appendix D to read "Appendix E"

The following Appendices A through G are also available on the web page as .pdf files that can

de downloaded and printed:

APPENDIX A: "WATSIM-DOE TEST.XLS" - SPREADSHEET TOOL TO

DETERMINE THE ENERGY PERFORMANCE CHARACTERISTICS

OF ELECTRIC STORAGE WATER HEATERS BASED ON OUTPUT

FILES FROM THE WATSIM COMPUTER SIMULATION MODEL

APPENDIX B: WATER HEATER ANALYSIS MODEL (WHAM) - METHOD FOR

DETERMINING WATER HEATER ENERGY CONSUMPTION

APPENDIX C: VENTING ISSUES IN GAS-FIRED WATER HEATERS

APPENDIX D: MANUFACTURER COST DATA FOR RESIDENTIAL

ELECTRIC AND GAS-FIRED WATER HEATERS

APPENDIX E: OIL-FIRED WATER HEATERS CONDUCTIVE HEAT LOSS

CALCULATION

APPENDIX F: ESTIMATES OF MANUFACTURING COSTS AND ENERGY

CHARACTERISTICS FOR ELECTRIC AND GAS-FIRED STORAGE

WATER HEATERS - DATA FROM MAX MINNIEAR

APPENDIX G: DESIGN OPTION COMBINATIONS

EE-RM-97-900 COMMENT 38TT
CONTENTS

OVERVIEW ................................................................. 7

REQUEST FOR STAKEHOLDER COMMENTS ................................. 7

LIST OF ACRONYMS ................................................... 9

INTRODUCTION .................................. ................. ..... 11

INFORMATION SOURCES .................................................. 11

BASELINE MODELS .................................................... 13

SCREENING ANALYSIS OF THE DESIGN OPTIONS ........................... 14

EFFICIENCY CALCULATIONS ............................................ 18

TECHNOLOGICAL ISSUES ................................................ 21

OVERALL ANALYSIS APPROACH ........................................... 26

ELECTRIC WATER HEATERS .............................................. 26

GAS-FIRED WATER HEATERS .............................................. 45

OIL-FIRED WATER HEATERS .............................................. 76

REFERENCES .............................................................. 97

EE-RM-97-900 COMMENT 38TT
Table 27. TANK Input Values providing acceptable EF and RE values ............... 49

Table 28. Gas-Fired Water Heater Baseline Model Characteristics .................. 49

Table 29. Gas-Fired Water Heater Modeling Differences: Existing Baseline Model vs.

Analytic Baseline M odel ................................................ 51

Table 30. Gas-Fired Water Heater Modeling Differences: Analytic Baseline Model vs.

Models with Metal and Plastic Heat Traps ................................ 51

Table 31. Gas-Fired Water Heater Modeling Differences: Analytic Baseline Model vs.

Models w/ 2 & /2 nominal in. of foam insulation .......................... 52

Table 32. Gas-Fired Water Heater Modeling Differences Analytic Baseline Model vs.

Model with Improved Flue Baffle ......... ................... ..... 54

Table 33. Gas-Fired Water Heater Modeling Differences Analytic Baseline Model vs.

Model with Electronic Ignition ......... .............................. 55

Table 34. Gas-Fired Water Heater Modeling Differences: Analytic Baseline Model vs.

Model with Electromechanical Flue Damper ............................... 56

Table 35. Side-Arm 40 gallon (150 liter) Gas-Fired Water Heater: Energy Factor

Estimates ............... .......................................... . 57

Table 36. Side-Arm 40 gallon (150 liter) Gas-Fired Water Heater, Plastic Tank: Energy

Factor Estimates ...................................................... 58

Table 37. Gas-Fired Water Heater Existing Baseline Model: Manufacturer Costs ...... 59

Table 38. Gas-Fired Water Heater Material Costs Associated with varying thicknesses of

HCFC-141b Foam Insulation ......... ................................ 59

Table 39. Gas-Fired Water Heater Material Costs Associated with varying thicknesses of

HFC-245fa Foam Insulation ............................................. 60

Table 40. Gas-Fired Water Heater Baseline Model with HCFC-141b and HFC-245fa:

Manufacturer Costs .................................................... 60

Table 41. Gas-Fired Water Heater Analytic Baseline Model with Resistant Flammable

Vapor Ignition Design: Manufacturer Costs ................ ............. 61

Table 42. Heat Traps for Gas-Fired Water Heaters: Incremental Manufacturer Costs

..................................................................... 61

Table 43. Increased Jacket Insulation for Gas-Fired Water Heaters: Incremental

M anufacturer Costs .................................................... 62

Table 44. Improved Flue Baffle for Gas-Fired Water Heaters: Incremental Manufacturer

Costs ................................................................ 62

Table 45. Electronic Ignition for Gas-Fired Water Heaters: Incremental Manufacturer

Costs ................................................................ 62

Table 46. Flue Damper w/ Electronic Ignition for Gas-Fired Water Heaters: Incremental

Manufacturer Costs ................ ........... .................. ..... 63

Table 47. Side-Arm Heaters for Gas-Fired Water Heaters: Incremental Manufacturer

Costs ................................................................ 63

Table 48. 40-Gallon (150 liter) Gas-Fired Storage Water Heater Retail Prices ......... 65

Table 49. 40-Gallon (150 liter) Gas-Fired Storage Water Heater Installation Costs ..... 66

Table 50. Cost Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater ........ 71

Table 50a. Cost Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater - Selected

Design Option Combinations ............................................ 72

Table 51. Efficiency Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater .... 73

Table 51a. Efficiency Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater -

EE-RM-97-900 COMMENT 38TT
TABLES

Table 1. Design Options Used in the Engineering Analysis ......................... 17

Table 2. Design Options Eliminated from Further Consideration .................... 17

Table 3. NAECA Minimum Efficiency Standards ................................. 19

Table 4. Conductivity Comparisons between Foam Insulation Blown with HCFC-141b and

HFC-245fa ........................................................... 22

Table 5. Summary of General Recommendations for Relining Exterior Masonry Chimneys

for Residential Installations in a Two-Appliance Configuration ............... 25

Table 6. Summary of General Recommendations for Relining Exterior Masonry Chimneys

for Residential Installations in a One-Appliance Configuration ................ 26

Table 7. Initial Existing Electric Water Heaters Baseline Characteristics* ............ 27

Table 8. Electric Water Heater Existing Baseline Model Characteristics* ............. 28

Table 9. Electric Water Heater Modeling Differences: Existing vs. Analytic Baseline

Model - Insulation Conductivity* ........................................ 30

Table 10. Electric Water Heater Modeling Differences: Analytic Baseline Model vs.

Models with Metal and Plastic Heat Traps* ............................... 32

Table 11. Electric Water Heater Modeling Differences: Analytic Baseline Model vs.

Models w/ 2 & 2V in. of foam insulation .................................. 32

Table 12. Electric Water Heater Modeling Differences: Analytic Baseline Model vs. Model

with Foamed Bottom Insulation* ......................................... 33

Table 13. Electric Water Heater Modeling Differences: Analytic Baseline Model vs. Plastic

Tank* ............................................................... 34

Table 14. Existing Electric Water Heater Material Costs Associated with varying

thicknesses of HCFC-141b Foam Insulation ............................... 35

Table 15. Foam Components Cost Estimate ...................................... 36

Table 16. Analytic Electric Water Heater Material Costs Associated with varying

thicknesses of HFC-245fa Foam Insulation ................................ 36

Table 17. Electric Water Heater Baseline Model with HCFC-141b and HFC-245fa:

M anufacturer Costs .................................................... 37

Table 18. Heat Traps for Analytic Electric Water Heaters: Incremental Manufacturer

Costs .......................................................... ...... 37

Table 19. Increased Jacket Insulation for Analytic Electric Water Heaters: Incremental

M anufacturer Costs .................................................... 38

Table 20. Insulating the Tank Bottom for Analytic Electric Water Heaters: Incremental

M anufacturing Costs ................................................... 38

Table 21. Plastic Tank Design for Electric Water Heaters: Incremental Manufacturer

Costs ................................................................ 39

Table 22. 50-Gallon (190 liter) Electric Storage Water Heater Retail Prices ........... 39

Table 23. 50-Gallon (190 liter) Electric Storage Water Heater Installation Costs ....... 41

Table 24. Cost-Efficiency Table for 50 gallon (190 liter) Electric Storage Water Heaters

..................................................................... 44

Table 25. Battelle Baseline Model Characteristics as presented at November 1997 GRI

TAG meeting ....................................................... 46

Table 26. TANK Input Variables: Approximate Impact on EF and RE ............... 48

EE-RM-97-900 COMMENT 38TT
Figures

Figure 1. 50 gallon (190 liter) Electric Storage Water Heaters: Total Consumer Cost and

Operating Cost vs. Energy Factor ........................................ 45

Figure 2. Energy Factor and Recovery Efficiency vs. Flue Baffle Effectiveness and Excess

Combustion Air ....................................................... 47

Figure 3. Gas Fired Water Heaters Design Option Selection Process ................. 71

Figure 4. 40 gallon (150 liter) Gas-Fired Storage Water Heaters: Total Consumer Cost and

Operating Cost vs. Energy Factor for Selected Design Options Combinations .... 76

EE-RM-97-900 COMMENT 38TT
Selected Design Option Combinations ..................................... 74

Table 52. Oil-Fired Water Heater Baseline Model Characteristics ................... 76

Table 53. Performance Characteristics for Existing Baseline Oil-Fired Water Heater ... 78

Table 54. Oil-Fired Water Heater Modeling Differences: Existing Model with HCFC-141b

vs. Analytic Model with HFC ............................................ 79

Table 55. Performance Characteristics for Analytic Oil-Fired Water Heater .......... 79

Table 56. Analysis Results for Design Option #1 (Heat Traps) ...................... 79

Table 57. Analysis Results for Design Options 2 - 2" Jacket Insulation .............. 82

Table 58. Analysis Results for Design Option 3 - Improved Flue Baffle ............... 82

Table 59. Analysis Results for Design Option 4 - Increased Heat Exchanger Area ...... 84

Table 60. Analysis Results for Design Option 5 - Interrupted Ignition ................ 87

Table 61. Cost Table for 32 gallon Oil-Fired Storage Water Heater Design Options .... 91

Table 62. Energy Impact and Simple Payback of Oil-Fired Water Heater Design Options

..................................................................... 94

Table 62a. Energy Impact and Simple Payback of Selected Oil-Fired Water Heater Design

Options ............................................................. 94

EE-RM-97-900 COMMENT 38TT

8

gas-fired water heaters

- manufacturer cost-to-retail price markup value

- incremental manufacturing cost for "Side-Arm Heater" design option

- issues regarding the use of a metal or plastic tank for "Side-Arm Heater" designs

- maintenance costs for "Side-Arm Heater" designs, due to fouling of the heat exchanger

- 10-year life for mechanical flue dampers in residential applications

- should fixed costs for 2.5 in. insulation scale with material cost?

oil-fired water heaters

- extended characterization of the baseline model characteristics

- manufacturer cost-to-retail price markup value.

EE-RM-97-900 COMMENT 38TT
9

LIST OF ACRONYMS

AGA American Gas Association

ADL Arthur D. Little, Inc.

AE098 Energy Information Administration's Annual Energy Outlook

ANOPR Advance Notice of Proposed Rulemaking

ANSI American National Standards Institute

ARI Air-Conditioning and Refrigeration Institute

Btu British thermal unit

CPI Consumer Price Index

CPSC Consumer Product Safety Commission

DOE U.S. Department of Energy

EF energy factor (from DOE's water heater test procedure)

EIA Energy Information Administration

EPACT Energy Policy Act of 1992

EPCA Energy Policy Conservation Act

EPA U.S. Environmental Protection Agency

EPRI Electric Power Research Institute

FR Federal Register

GAMA Gas Appliance Manufacturers' Association

GRI Gas Research Institute

GRIM Government Regulatory Impact Model

HCFC hydrochlorofluorocarbon

HFC hydrofluorocarbon

HSI hot surface ignition

IRR Internal Rate of Return

LBNL Lawrence Berkeley National Laboratory

LCC life-cycle cost

LPG liquefied petroleum gas

MMBtu million Btu

MCF thousand cubic feet

NAECA National Appliance Energy Conservation Act

NES National Energy Savings

NFGC National Fuel Gas Code

NIST National Institute of Standards and Technology

NOAA National Oceanic & Atmospheric Administration

PNNL Pacific Northwest National Laboratory

PVC polyvinylchloride

RE recovery efficiency (of a water heater)

RECS Residential Energy Consumption Survey

SCF standard cubic foot

SG&A Cost Selling, General & Administration Cost

TAG Technical Advisory Group

TSD Technical Support Document

UA Standby Heat Loss Coefficient

UEC unit energy consumption

USC United States Code

WHAM Water Heater Analysis Model

EE-RM-97-900 COMMENT 38TT
10

This page intentionally left blank.

EE-RM-97-900 COMMENT 38TT
11

INTRODUCTION

The Energy Policy and Conservation Act, as amended, provides energy conservation

standards for water heaters among other products and authorizes the Secretary of Energy to

prescribe amended or new energy standards for each type of covered product. This is a

preliminary Engineering Analysis; it is part of the analyses the Department will conduct for the

water heater rulemaking. The preliminary life-cycle cost analysis will be provided later this

month.

The objective of the Engineering Analysis is to determine the costs of increased energy

efficiency for residential water heaters by developing price and efficiency data for design options

and combinations of design options for each product class. This information will be used in

subsequent components of the standards rulemaking process. The results of the Engineering

Analysis are summarized in cost-efficiency tables demonstrating the increased cost and

efficiency due to each design option within each product class. Appendices A through G that are

referenced in this report.

This report describes the analysis of cost and efficiency impacts of specific design options

and combinations of design options. Design options used in this analysis are the results of a

technology assessment and screening analysis, and comments from stakeholders.

The Engineering Analysis uses computer simulation models and other analytical methods

to investigate the efficiency improvements of design options and interactions when multiple

design options are used. The Engineering Analysis is based on the U.S. DOE Test Procedure for

residential water heaters with a daily draw of 64.3 gallons (243.4 liters), a setpoint of 135 °F

(57.2 C), an inlet water temperature of 58°F (14.4°C), and an ambient air temperature of 67.5°F

(19.7 0C) 2

Manufacturer, distributor and installer markups are applied to factory costs as is sales tax

to arrive at the purchase price of the water heater. A fixed markup is derived from retail price

data for existing baseline water heater models and applied to manufacturer costs in order to

determine consumer prices of design options. Additional installation and costs required for

certain design options are also included in the final price for these design options.

Energy prices are the current national average energy prices from the Energy Information

Administration's Annual Energy Outlook 1998 (AE098) 3.

INFORMATION SOURCES

The primary source of both manufacturer cost and efficiency data for this analysis was the

Gas Appliance Manufacturers' Association (GAMA) (See Appendix D). GAMA collected cost

and efficiency data from water heater manufacturers. The data was aggregated to protect the

confidentiality of the individual manufacturers. GAMA did not provide data for three of the

design options being considered (2.5 in. of insulation, plastic tank & side-arm heater). The

EE-RM-97-900 COMMENT 38TT
12

missing data was supplemented by cost and efficiency information obtained from Max E.

Minniear, former Vice President of Engineering at A. O. Smith Water Products Company. Mr.

Minniear was contracted by Lawrence Berkeley National Laboratory (LBNL) to provide

disaggregated cost and efficiency data for baseline designs and various design options (See

Appendix F). Some of the cost data was also compared with data obtained from Eugene West,

formerly of Bradford-White Corporation, who was under contract with Pacific Northwest

National Laboratory (PNNL). Mr. Minniear and Mr. West were both recommended by the Gas

Appliance Manufacturers Association (GAMA).

Although computer simulation models were used to generate the efficiency gains

expected from design options, GAMA and Mr. Minniear's efficiency estimates were used to

confirm the reasonableness of the models' estimates. Other sources of information were used as

well. One key source of efficiency data was the GAMA directory 4. The directory lists energy

factor (EF), recovery efficiency (RE), rated input, and first hour rating for residential water

heating equipment. The Department accepts listing in the GAMA directory as certification that a

model meets the minimum allowable efficiency. Manufacturers' product literature was also

collected. It provided additional information about certain design features (e.g., heat traps and

thickness of foam insulation). Product literature data were mapped to listings in the GAMA

directory to determine what efficiency improvements were employed to reach particular

efficiency levels.

Independent confirmation of manufacturer cost data was conducted for certain design

options by contacting component manufacturers. In particular, this was done for heat traps and

foam insulation. An upper limit to the factory cost of baseline model water heaters was extracted

from census data5. Factory cost is the manufacturer's cost to make water heaters and includes

material, labor, and overhead. The Census Bureau Survey of Manufacturers, Major Household

Appliances (MA36F), 1995, reports total value of gas-fired and electric water heaters as $920

million for 8.07 million units sold. This gives an average price per unit of $114. Since this data

includes premium models and the manufacturer's markups, as well as warranty costs, freight,

profits and commissions, it will be higher than the baseline model factory cost, but it provides an

upper limit.

The cost to the consumer for the water heater equipment and the installation cost was

established by contacting various plumbing contractors and large retail chains (e.g., The Home

Depot, Lowe's, Ferguson, Orchard) throughout the United States.

Other reports, such as the Gas Research Institute (GRI) report, Assessment of Technology

for Improving the Efficiency of Residential Gas Water Heaters6 and the Arthur D. Little report,

Market Disposition of High-Efficiency Water Heating Equipment7, were used to confirm the

reasonableness of the cost, price, and efficiency data. The above GRI report was specifically

used to establish the installation cost of gas-fired water heaters requiring an electrical hookup and

to estimate the maintenance cost associated with electromechanical flue dampers.

EE-RM-97-900 COMMENT 38TT
13

BASELINE MODELS

The determination of product classes and selection of baseline units for the analysis is

based on existing DOE water heater efficiency standards8 and stakeholder comments. The

baseline unit represents the most common size water heater with an efficiency equal to the

minimum allowed by the existing energy efficiency standards. The general characteristics of

each baseline model for each of the three primary product classes (i.e., electric storage, gas-fired

storage, and oil-fired storage) are provided below. An in-depth description of each of the

baseline models is provided later in this report.

Electric Storage Water Heaters

The baseline model is a 50 gallon (190 liter) glass-lined steel tank with 1/2 in. (3.8 cm) of

polyurethane foam. The heater has two elements, each with an input of 4500 W. The elements

are interlocked so that only one can be energized at a time. The baseline energy factor is 0.86,

the National Appliance Energy Conservation Act (NAECA) minimum for this size and type of

water heater.

Gas-Fired Storage Water Heaters

The baseline model of gas-fired storage water heaters is a bottom-fired, 40 gallon (150

liter), glass-lined steel tank with a 4-in. (10 cm) center flue. The input rate is 40,000 Btu/hr

(11,700 W), with a pilot rated at 400 Btu/hr (120 W). The tank is insulated with 1 in. (2.5 cm) of

polyurethane foam. The heater has the minimum efficiency allowed by NAECA with an energy

factor of 0.549. It has a recovery efficiency of 76%.

Oil-Fired Storage Water Heaters

The baseline oil-fired water heater is a center-flue design. It has a rated volume of 32

gallons (120 liters), and is insulated with 1 in. (2.5 cm) of polyurethane foam insulation. The

input rate is 0.65 gallons per hour (2.5 liters/hr) of oil or 90,000 Btu/hr (26,000 W). It has an EF

of 0.53, the minimum allowed by NAECA. The first hour rating is 105 gallons (398 liters), and

the RE is 75%. The tank is a cylinder 18 in. (46 cm) in diameter and 32.7 in. (83.1 cm) high,

pierced by a 6 in. diameter (15 cm) flue along the central axis. The burner motor, which powers

both the blower and oil pump, is rated at 1/8 hp (282 W). No auxiliary power is consumed during

standby. The ignition system on the baseline model is assumed to be the intermittent type and

uses a conventional magnetic transformer to achieve the high voltage spark.

EE-RM-97-900 COMMENT 38TT
14

SCREENING ANALYSIS OF THE DESIGN OPTIONS

The first step in the rulemaking process is the screening of design options. The purpose

of screening is to identify those design options that the Department will consider for the

engineering analysis. The screening analysis also provides a discussion of the criteria for

eliminating certain design options from further consideration. On July 15, 1996, the Department

issued the Process Improvement (Interpretive) Rule (61 FR 36974, July 15, 1996) which

establishes the factors DOE uses for screening design options. The factors are as follows:

* Technological feasibility.

* Practicability to manufacture, install and service.

* Adverse impacts on product utility or product availability.

* Adverse impacts on health and/or safety.

In accordance with the Process Improvement Rule, the Department published the

results of a preliminary screening of the water heater design options in "Technology

Assessment and Screening Analysis, Appendix B Supplement to the Water Heater

Rulemaking Framework", January 1998. Stakeholders were notified of the availability of

this document in the Federal Register on January 14, 1998 (63 FR 2186). The Notice further

requested comments on the Technology Assessment and Screening Analysis document.

Comment Summary: DOE received 28 comments on the Technology Assessment and

Screening Analysis document. Six stakeholders including GAMA supported, with

modifications, the Department's position regarding the screened design options. The

comments addressed air atomized oil burners, power vents and tank bottom insulation for gas

or oil-fired water heaters. The majority of comments dealt with the Department's decision to

eliminate the heat pump water heater design option from consideration. Those comments

from the American Gas Association (AGA) and some gas utilities claimed that DOE must

consider all technologically feasible design options to comply with the law (42 U.S.C. Section

6295).

Changes to the Screened Design Options: The baseline electric unit for the present analysis

has been assumed to have 1.5 in. of jacket insulation (rather than the 1.0 in. assumed for gasand oil-fired water heaters) in order to achieve the baseline EF levels. Increasedjacket

insulation levels will be considered in the engineering analysis based on these baseline

assumptions. Heat traps could be either of plastic or metallic design. Manufacturing costs

appear to be roughly comparable between the two, but plastic heat traps are considerably more

effective in reducing the water heater standby losses. Therefore, the present engineering

analysis will only consider plastic heat traps as a design option. Air Atomized Burners were

included in the set of design options DOE proposed for consideration in the rulemaking for

oil-fired water heaters. However, based on stakeholder comments, the Department has

decided not to consider air atomized burners further because they aren't practical to

manufacture. A prototype of the air atomized burner has been developed for oil-fired furnaces

but the design has not yet been applied to water heaters and the work is being closely followed

EE-RM-97-900 COMMENT 38TT
15

by the oil-fired water heater industry.

A power vent design was included as part of the discussion of the Improved Flue

Baffle design option. However, DOE will not consider the power vent design because it

requires special venting systems that may not be practical in all situations. Although the

American Council for an Energy Efficient Economy claims that this design can go above the

80% RE limit without requiring corrosion resistant flues, the Department believes that any

designs above 80 % RE could result in corrosion inside the water heater in colder climates.

Increased Heat Exchanger Surface Area was included in the set of design options the

Department proposed to consider. Manufacturers stated that the same efficiency improvement

can be achieved by Improved Flue Baffles and that this is the preferred approach for

residential water heaters.

Additionally, Increased Heat Exchanger Surface Area in the form of finned flue

surfaces, is being considered as a design option for oil-fired water heaters. Because oil-fired

units have a higher input capacity, they can benefit from both improved flue baffles and

increased heat exchanger surface areas.

Electric utilities requested that the Department consider the Tank Bottom Insulation

option for gas or oil-fired water heaters as well. However, DOE has decided not to consider it

for safety reasons. The tank bottom is the burner enclosure for gas or oil-fired water heaters,

and the high temperatures would pose a safety hazard due to melting insulation.

The gas utility industry would like DOE to consider the Heat Pump Water Heater

design option. However, the gas utility industry didn't provide any new information to cause

DOE to reconsider its earlier decision. The Interpretive Rule addresses how those design

options, that are not practicable to manufacture, install and service, should be eliminated from

consideration in the engineering analysis. In particular, there are three different sections of the

Rule that urge the Department to: (III)(l)(d) "eliminate problematic design options early in

the process;" (j) "reduce time and cost of developing standards;" and (III)( 11) "be sensitive to

first cost increases...avoiding negative impacts to identifiable population groups." Further, the

design is not to have adverse impacts on product utility. Providing an equivalent capacity unit

(equal to the base case capacity for the electric water heater design) would increase the first

cost of the electric water heater significantly. This is also true because heat pumps, in general,

are not very efficient at low temperatures < 50°F (<10°C) and present designs may not have

sufficient capacity to meet normal hot water loads, and hence, may require an electric

resistance backup. A Federal Technology Alert'° issued on the use of residential heat pump

water heaters at federal sites shows that they are cost-effective only in select regions of the

United States when compared to electric resistance water heating. Since a standard can only

cover products which can be practically applied to all situations, the heat pump water heater's

adverse impact on consumer utility and lack of adequate servicing infrastructure weighed

heavily in the earlier recommendation. Surveys from the Georgia Power and Alabama Power

companies reported that over 50 % of their customers would have difficulty installing a heat

EE-RM-97-900 COMMENT 38TT
16

pump water heater because of space limitations (Arthur D. Little, Inc. 1996"). Additionally,

many comments to the 1994 Notice of Proposed Rulemaking (59 FR 10464, March 4, 1994)

claimed that it was difficult to find people trained to service a heat pump water heater in rural

and low-income areas.

AGA argues that DOE relied on "unsubstantiated and uncorroborated" explanations by

interested parties in reversing its decision, when in fact, the proposal to keep electric heat

pump water heaters as a design option prompted an unprecedented torrent of negative

comments following the issuance of the proposed rule in 1994. They are summarized as

follows:

* 33 comments questioned the reliability of heat pump water heaters.

* 15 comments cited the space restrictions of small homes, and the increased payback

time due to reduced water use.

* 216 comments cited the immature infrastructure for manufacturing, sales and repair,

especially in rural areas.

* 66 comments questioned the inconvenience and possible price hikes for larger tank

size due to the lower recovery rate, 40 % slower than conventional electric water

heaters.

* 21 comments believed it would distort the marketplace and lessen competition

among fuel sources.

* 33 comments expressed concerns about increased noise.

* 107 comments feared increased electric rates due to loss of revenues in rural electric

cooperatives.

* 22 comments claimed under-the-counter applications would not be cost effective.

Since the late 1970s, when efforts to develop and commercialize heat pump water

heaters began, annual sales have not exceeded 10,000 heat pump water heaters (<0.33% of

electric water heater sales, <0.17% of all water heater sales). Sales have declined drastically

since the mid-1980s, and recent sales are less than 0.1% of all electric water heaters sold. No

mass market distribution, sales, installation and servicing infrastructure exists. There is no

precedent in the history of the U.S. major appliance industries to suggest that a complete

reversal of this situation, on the scale of several million units per year, in only a few years, and

in the absence of consumer demand, is possible. Such a reversal would be required if an

energy efficiency standard at the heat pump water heater level for electric water heaters is

proposed.

EE-RM-97-900 COMMENT 38TT
17

The heat pump water heater being developed by DOE does not overcome all of the

consumer utility issues because it is designed with a lower recovery rate for average to low hot

water usage households. Finally, the Department is concerned that including the heat pump

water heater design option could interfere in the market balance between gas and electric

utilities.

Table 1 is a list of design options being considered for the engineering analysis (for

discussion of option contraints considered see Appendix G) and Table 2 is a list of design

options that have been eliminated from further consideration.

Table 1. Design Options Used in the Engineering Analysis

Design Options - Description Gas Electric Oil

Heat Traps X X X

Plastic Tank X( X

Increased Jacket Insulation X X X

Insulating the Tank Bottom X

Improved Flue Baffle X X

Increased Heat Exchanger Surface Area X

Flue Damper (Electromechanical) X

Side-Arm Heater X

Electronic (or Interrupted) Ignition X X

(1) used in conjunction with the side-arm heater option

Table 2. Design Options Eliminated from Further Consideration

Design Options -- Description Criteria for Elimination

Flue Damper (Buoyancy Operated) Safety issues and lack of long-term use data

Submerged Combustion Conflict with health and safety codes

Directly Fired Conflict with health and safety codes

Condensing Option Venting application restrictions

Condensing Pulse Combustion Venting application restrictions

EE-RM-97-900 COMMENT 38TT
18

Design Options - Description Criteria for Elimination

Power Vents Venting application restrictions

Advanced Forms of Insulation Fails the practicability to manufacture

criterion

U-Tube Flue Lack of working prototypes and conflict with

safety codes

Thermophotovoltaic and Thermoelectronic Lack of application to water heaters

Generators

Reduced Burner Size (Slow Recovery) Adverse impact on product utility and venting

application restrictions

Heat Pump Water Heater Options Lack of service and installation infrastructure

and product utility concerns

Timer Controlled Not an efficiency improvement option

System Application Options System installation feature

Increased Heat Exchanger Surface Area Not as cost effective as the Improved Flue

Baffle design option for gas-fired units

Air-Atomized Oil Burner Not practical to manufacture and lack of

application to water heaters

Sediment Removal Features Not an efficiency improvement option

Two-Phase Thermosyphon (TPTS) Design Fails the practicability to manufacture

EFFICIENCY CALCULATIONS

The energy performance of the baseline unit is mandated by the NAECA minimum

efficiency standards, which have been in effect since 199112 (Table 3).

EE-RM-97-900 COMMENT 38TT
19

Table 3. NAECA Minimum Efficiency Standards

Product Class Minimum Allowable Energy Factor (as of April 15, 1991)

Gas-fired Water Heater 0.62 - (.0019 x Rated Storage Volume in gallons)

Oil-fired Water Heater 0.59 - (.0019 x Rated Storage Volume in gallons)

Electric Water Heater 0.93 - (.00132 x Rated Storage Volume in gallons)

Note: Rated Storage Volume = the water storage capacity of a water heater, in gallons, as specified by the

manufacturer.

The design options for each of the three classes of water heaters were modeled either

with computer simulation programs or an energy calculation method. The output from the

computer simulations was used to determine the energy efficiency characteristics of the water

heater (e.g., the EF, RE, and standby heat loss coefficient (UA)), based upon the DOE test

procedure. The simulation models and energy calculation methods that were used are

discussed briefly below.

WATSIM Model for Electric Storage Water Heaters

WATSIM is a detailed electric water heating simulation program developed by EPRI'3 .

WATSIM contains two simulation algorithms; one for the detailed simulation of water heater

tanks and the other for controlling water draw profiles for use with the tank model. Since the

simulation analysis must be performed according to the requirements of the DOE test

procedure, the water draw profile is specified to the 64.3 gallon (243.4 liter) draw pattern in

the test procedure. The output of WATSIM does not include the EF, RE, and UA calculations

from the DOE test procedure. However, it does provide detailed temperature profiles of the

water inside the tank of the water heater during the simulation run (the temperature profile is

provided in a standard WATSIM output file called tw_vs_tl.out). These temperature readings

are used to determine the EF and other parameters of the water heater using the test procedure

calculations. A spreadsheet tool has been developed to calculate the efficiency characteristics

per the specifications of the DOE test procedure from the output contained in the

tw_vstl.out file. Appendix A provides a detailed description of the procedure to determine

the efficiency characteristics using the WATSIM output.

TANK Model for Gas-Fired Storage Water Heaters

TANK is a detailed gas-fired storage water heater program developed by Battelle for

the GRI'4 . TANK calculates energy flows throughout the water heater including heat gained

or lost by the water, flue heat losses, jacket heat losses, fittings heat losses, and combustion

chamber heat losses. Unlike WATSIM, the outputs of TANK include the EF, RE, and UA

EE-RM-97-900 COMMENT 38TT
20

from the DOE test procedure. Therefore, calculations outside of TANK are not necessary for

determining the gas-fired water heater's energy efficiency characteristics under DOE test

procedure.

As will be discussed in more detail later, there are limits to how high the flue-loss

efficiency can be increased before changes are required of the vent system to prevent flue gas

condensation. Recent discussions with Battelle' 5 indicate that TANK may provide inaccurate

estimates of the flue-loss efficiency. However, because of insufficient data, DOE has decided,

for now, to rely on TANK predictions. Therefore the Engineering Analysis will continue to

use TANK's estimates of the flue-loss efficiency to indicate whether modifications to the vent

system are necessary.

WHAM Energy Calculation for Oil-Fired Storage Water Heaters

A simplified water heater analysis model (WHAM) was used for the Engineering

Analysis for oil-fired water heaters. WHAM is based on the 24 hour simulated use test

portion of the DOE test procedure. The model is an equation to calculate energy consumption

from the RE, UA, and rated input (Pon) 16. The WHAM energy calculations have been checked

against both the WATSIM and TANK simulation models to verify that the energy

consumption calculations are sufficiently accurate. The WHAM energy calculation is based

on an idealized version of a water heater. The water temperature is assumed to remain at the

setpoint throughout the tank. Also RE and UA are assumed to be constant. The equation is

listed below.

Q vol dens- Cp (Ttank - Tin) .[ UA (Ttank - Tmb)

where;

Qin = average daily energy input,

RE = recovery efficiency from test procedure,

UA = standby heat loss coefficient from test procedure,

Pn, = rated input,

vol = average volume of water drawn in 24 hours,

T,,,k = tank thermostat set point,

Tm = inlet water temperature,

Tamb = ambient air temperature surrounding the water heater

dens = density of water, and

Cp = specific heat of water.

Daily energy use predictions from WHAM for oil-fired water heaters were not directly

compared against daily use predictions from any oil-fired water heater simulation model (such

as TANK or WATSIM) as no simulation model exists for oil-fired water heaters. However,

the results of the WHAM equation have been compared against results of detailed simulation

models of residential electric and gas-fired storage water heaters with excellent agreement. A

EE-RM-97-900 COMMENT 38TT
21

detailed explanation of the WHAM approach is included in Appendix B.

It is believed that WHAM is a good predictor of daily energy use for oil-fired water

heaters because one of the simplifying assumptions is that all the water drawn from the tank

is at the set point temperature. For a given draw volume (such as the separate 10.7 gallon

(40.5 liter) draws of the DOE test), the oil-fired water heater will fire at approximately the

same time as would a gas-fired water heater of similar volume. However, since the recovery

rate of oil-fired water heaters is typically over twice that of residential gas fired water heaters,

the temperature of the water being drawn from the heater will, on average, be closer to the

water heater set point temperature.

TECHNOLOGICAL ISSUES

There are impending regulatory changes outside of the NAECA efficiency standards

process that will impact the manufacture or installation of water heaters. Some of these

changes affect the efficiency of water heaters as well. These issues are described here, along

with the methods that were used to address each issue.

Insulation

Most residential water heaters are insulated with polyurethane foam in the space

between the tank and the jacket. The insulation is foamed in place using polyols and

isocyanates that react to form a polyurethane foam. A blowing agent included in the mixture

is vaporized by the heat of reaction creating a frothy mass that hardens quickly into closed-cell

foam insulation. Currently, water heater manufacturers use HCFC-141b, an ozone depleting

substance, as a blowing agent. As a result of the Montreal Protocol, the U.S. Environmental

Protection Agency has scheduled the phase out of this blowing agent by the year 2003 7.

Water heater manufacturers must use another blowing agent after that time.

One of the leading alternatives for use as a blowing agent appears to be HFC-245fa.

This blowing agent is being adopted by the refrigerator industry and should be available in

sufficient quantity by 2003. At the temperatures found in water heaters, information from

Bayer and Battelle reports shows that it does have a slightly higher k-factor than the current

blowing agent'8 '9. Based on this information, Table 4 presents conductivity comparisons of

foam insulation blown with HCFC-141b and HFC-245fa. The average increase in

conductivity resulting from replacing HCFC-141b with HFC-245fa is 3.0%.

EE-RM-97-900 COMMENT 38TT
22

Table 4. Conductivity Comparisons between Foam Insulation Blown with HCFC-141b and

HFC-245fa

Conductivity @ 100°F (37.8°C)

HCFC-141b HFC-245fa

Source Type of Foam Panel Btu-in/hrft- °F (W/m-K) Btu-in/hrft °F (W/m-K)

Bayer 5% pack, 2 in. (5.1 cm) panel 0.149 (0.0214) 0.151 (0.0218)

Bayer 10% pack, 2 in. (5.1 cm) panel 0.148 (0.0212) 0.154 (0.0221)

Bayer 5% pack, 3 in. (7.6 cm) panel 0.152 (0.0220)' 0.155 (0.0223)

Bayer 10% pack, 3 in. (7.6 cm) panel 0.150 (0.0217)' 0.154 (0.0221)

Bayer not specified 0.146 (0.0211) 0.154 (0.0221)

Battelle not specified 0.166 (0.0239) 0.172 (0.0247)

Average Conductivity Increase 3.0%

The analysis for the DOE water heater energy efficiency standards is based on the

properties of insulation blown with HFC-245fa and the most realistic estimates of costs and

physical parameters available for HFC-245fa. In order to keep the efficiency and energy use

characteristics of water heaters with HFC-245fa insulation the same as those with HCFC-141b

insulation, it was necessary to compensate for the 3.0% higher k-factor. This was

accomplished by modeling the water heaters with slightly thicker insulation. In addition to the

extra volume and cost of insulation, the amount and cost of steel used for the water heater

jacket were also increased.

The industry is also considering other blowing agents in addition to HFC-245fa

including HFC-356mffm, HFC-134b, cyclo-pentane, and water blown foams. Water blown

foams are created when water is mixed into one of the components and participates in the

chemical reaction leading to polyurethane causing the release of CO2 which provides the

blowing activity. Although the above blowing agents are currently being investigated as

possible replacements to HCFC-141b by the water heater industry, the analysis presented in

this report is based on the use of HFC-245fa.

DOE, in collaboration with the National Institute of Standards and Technology (NIST)

and Pacific Northwest National Laboratory, is testing the relative performance of HCFC-141 b,

HFC-245fa and water-CO2 foam blowing agents on water heater performance. The approach

of the analysis is to measure the thermal conductivity of blocks foamed with each blowing

agent in a guarded hot plate test, and perform a DOE 24-hour simulated use test on tanks

foamed with each blowing agent. Twelve 50-gallon (190 liter), dual-element electric water

heater tanks were provided by Bradford White and shipped to BASF, a foaming supplier for

foaming. BASF foamed a set of four samples (consisting of four tanks and four blocks) with

each blowing agent. The foaming of tanks with each blowing agent was timed to ensure a

similar aging period has passed prior to the time they are tested. The foaming was carried out,

to the extent possible, in accordance with standard industry practices. BASF, on the basis of

their expertise and experience, and in consultation with industry experts, determined the

EE-RM-97-900 COMMENT 38TT
23

appropriate parameters regarding the formulation of the resin and blowing agent material. The

samples, consisting of foam blocks and tanks were shipped to NIST where the following tests

were conducted:

Guarded Hot Plate: A one meter guarded hot plate operated in two-sided mode was

used to measure the thermal conductivity of the insulation blocks. The cold plates

were set to 67.5 F (19.7 C). Thermal conductivity measurements were made at hot

plate temperatures of 100.0°F (37.8°C), 120.0°F (48.9°C), and 140.0°F (60.0°C).

DOE 24-Hour Test: NIST used the DOE 24-hour simulated use test to determine EF.

The EF test was conducted on at least three of the four tanks. An infrared camera was

used during the DOE test to inspect for gross voids or bridges in the tank insulation. If

the infrared inspections and EF results were consistent between samples of a given

blowing agent type, NIST could, at its discretion, eliminate the fourth tank from the

testing sequence.

All final results of the tests will be fully documented and provided to the DOE. The

test results will be used to verify the assumed thermal conductivities of the foam insulations

used in the Engineering Analysis. Subsequent revisions to the Engineering Analysis will

update the insulation conductivities as dictated by the test results.

Flammable Vapor Ignition

Current designs for gas-fired water heaters rely on a standing pilot to ignite the main

burner. If flammable vapors are in the air near a water heater, there is the possibility of

unintended ignition. This is a potential safety problem because water heaters are often

installed in garages and basements, where flammable liquids such as gasoline or paint thinners

may be used.

The Consumer Product Safety Commission (CPSC) is working with GRI and the water

heater industry to develop a test procedure for gas-fired water heater designs that will prevent

ignition of flammable vapors20. American National Standards Institute (ANSI) is anticipated

to adopt a test procedure regarding water heater resistance to igniting flammable vapors in

1999.

From discussions with the Water Heater Industry Joint Research and Development

Consortium, DOE will use a placeholder value of $35 as additional cost for designs to prevent

ignition of flammable vapors. In this analysis, the extra $35 is applied to the manufacturer

cost of all design options for gas-fired water heaters, including the baseline design. Thus, the

added cost of preventing flammable vapor ignition does not impact the cost effectiveness of

any energy efficiency design improvement. The design is also assumed not to require

electricity at the water heater or modifications of the venting system. No changes in efficiency

are expected from flammable vapor ignition resistant water heater designs. This situation will

EE-RM-97-900 COMMENT 38TT
24

be monitored to verify these assumptions or to update the analysis as designs meeting the

ANSI standard become available.

Venting

Use of gas-fired water heaters with flue-loss efficiency greater than 80% with existing

venting systems that are not designed for low temperature flue gases can potentially lead to

excessive corrosion and failure of the vent system 2122 in certain climates. The Department

has recognized this potential problem and decided to incorporate, where necessary, the costs

of venting modifications to gas water heater installation costs. In this section,

recommendations derived from previous studies conducted by the gas industry are outlined.

Appendix C of this report provides more details on the impacts of using high-efficiency water

heaters on vent system corrosion and its prevention.

GRI has estimated that 53% of U.S. residences have common vent systems for water

heaters and furnaces (Paul 1991). With increased minimum furnace efficiency requirements

(since 1992), most replacement furnaces have a higher efficiency than the existing units they

are replacing. Although masonry chimneys are quite resilient to corrosion, relining may be

necessary when an existing low flue-loss efficiency (<80%) furnace is replaced with a high

flue-loss efficiency furnace (>80%). Because furnace on-times are significantly higher than

water heater on-times, the furnace usually dries any condensate deposited in the masonry

chimney by the water heater. With the use of high flue-loss efficiency furnaces, the flue gas

temperatures are lower, increasing chimney wet-times.

Most water heaters sold today are for the replacement market. In almost all replacement

situations, there are vent systems and reliners available in the market to meet the venting

requirements for installing high flue-loss efficiency water heaters. Hence, there is no

technological barrier to use a high flue-loss efficiency water heater in a replacement situation.

Table 5 summarizes the recommendations for a two-appliance configuration. A base

case configuration is assumed to have two natural draft appliances (a furnace and a water

heater, for example) venting into a common vent system. The flue-loss efficiency of each of

these units is assumed to be less than 80%. The vent connectors are assumed to be single wall

metallic connectors and the vent is assumed to be an exterior masonry chimney that is

properly sized.

Table 6 summarizes the recommendations for a one-appliance configuration. A base

case configuration is assumed to have a natural draft water heater venting into an exterior

masonry vent system. The flue-loss efficiency of the unit is assumed to be less than 80%. The

vent connectors are assumed to be single wall metallic connectors and the vent is assumed to

be an exterior masonry chimney that is properly sized. This table shows that design options

and combinations of design options, which result in a flue-loss efficiency of 80% or less can

be vented into systems that follow the National Fuel Gas Code 23 standards for venting

systems with no additional cost.

EE-RM-97-900 COMMENT 38TT
25

Table 5. Summary of General Recommendations for Relining Exterior Masonry Chimneys

for Residential Installations in a Two-Appliance Configuration

Option Comment

Base case: both furnace and water heater

flue-loss efficiency less than 80% No relining is necessary

Replace base case water heater with 80.5%

efficient (flue-loss) unit No relining is necessary

Replace base case water heater with 83% Relining may be needed in most DOE

efficient (flue-loss) unit regions

Replace base case furnace with 83% Relining of the chimney is recommended in

efficient (flue-loss) unit (fan-assisted) all regions except DOE region I (Phillips

1994)

If the flue-loss efficiency is between 80.5%

and 83%, chimneys in some DOE regions

Replace base case water heater and furnace may need relining. If the flue-loss

with high flue-loss efficient units efficiency is above 83%, relining is

recommended in all regions except region

DOE region I.

"Orphaned" water heater Relining is recommended in all DOE

regions

EE-RM-97-900 COMMENT 38TT
26

Table 6. Summary of General Recommendations for Relining Exterior Masonry Chimneys

for Residential Installations in a One-Appliance Configuration

Option Comment

Base case: flue-loss efficiency of the water

heater is less than 80% No relining is necessary

Replace base case water heater with 80.5%

efficient (flue-loss) unit No relining is necessary

Replace base case water heater with 83% Relining may be needed in most DOE

efficient (flue-loss) unit regions, except DOE region I

Another important consideration is the configuration of the vent connector - the

portion of the vent system connecting the gas appliance flue collar or draft hood to the vent. A

single wall vent connector limits the flue-loss efficiency of gas appliances to 80% in a worst

case installation. Therefore, if the flue-loss efficiency of the water-heater or the furnace (twoappliance configuration) exceeds 80% it is recommended that a double wall vent connector be

used (Paul et al. 1992, Talbert et al. 1995).

OVERALL ANALYSIS APPROACH

In this report, a distinction has been made between baseline models containing current

technologies and future baseline models which are expected to incorporate new mandated

features. The former are referred to as "existing" baseline models and the latter as "analytic"

baseline models. An important feature of existing water heater technology is the insulation

based on HCFC-141b as a blowing agent. Additionally, for the purposes of the analysis, a

representative, or "typical" tank size (rated volumes of 50-gal for electric, 40-gal for gas-fired,

and 32-gal for oil-fired) has been chosen from all the standard sizes for each fuel type. The

first half of this discussion concerning costs and prices will address only the typical existing

baseline models.

ELECTRIC WATER HEATERS

The Engineering Analysis models the design options for electric water heaters using

WATSIM, a detailed computer simulation model for water heaters developed by EPRI. A 50

gallon (190 liter) rated volume electric resistance water heater is used as the existing baseline

model for this analysis.

EE-RM-97-900 COMMENT 38TT
27

Existing Typical Baseline Model

In using WATSIM to establish the typical existing baseline model, the goal was to

establish the characteristics of a 50 gallon (190 liter) baseline electric water heater which

would yield a 0.86 EF (the minimum EF allowed by NAECA for a 50 gallon electric water

heater).

GAMA's directory of certified water heaters and product literature from various

manufacturers shows three models of 50 gallon (190 liter) electric water heaters with an

energy factor of 0.86. Two models accomplished this through the use of heat traps and 1 in.

(2.5 cm) of foam insulation (American E51-50H-045D and Bradford White M-I-50T6DS)

while one model achieved a 0.86 EF solely through the use of 1 in. (2.5 cm) of foam

insulation (Rheem 81V52D). It should be noted that the foam insulation in the above models

is blown with HCFC-141b. Since the literature indicated that a 0.86 EF was achievable solely

through the use of 1 in. (2.5 cm) of foam insulation, the first typical existing baseline water

heater modeled incorporated only this single energy-efficiency design feature. Table 7

summarizes the primary characteristics of the typical existing baseline water heater first

simulated with WATSIM.

Table 7. Initial Existing Electric Water Heaters Baseline Characteristics*

Tank Diameter 15.84 in. (40.23 cm)

Tank Length 54.48 in. (138.38 cm)

Insulation Thickness - Sides 1.00 in. (2.54 cm)

Insulation Thickness - Top 1.00 in. (2.54 cm)

Conductivity of Feed-Throughs (equivalent to steel) 0.40 Btu/ft-min °F (41.54 W/mnK)

Natural Convection UA for Feed-Through calcs (no heat traps) 0.578 Btu/hr- F (default in WATSIM)

Note: * Units in the table are consistent with the units used by the WATSIM simulation model.

Simulations of a water heater with the baseline characteristics listed in Table 7 yielded

a surprisingly low EF of 0.805. WATSIM's simulation results were then compared to those

from TANK (GRI's gas-fired water heating simulation model) to determine the cause of its

low EF estimate. For comparably sized water heaters, WATSIM's pipe heat loss estimates

were approximately twice that of TANK's. Since during TANK's development its

performance was validated against actual test data, WATSIM's method for calculating feedthrough losses was suspected of being inaccurate. To confirm this, additional simulations

were conducted to determine whether any specific water heater characteristics could

significantly impact EF, thereby ruling out the high feed-through losses as being the cause of

the low EF estimate. But the simulations could not identify any physical parameters, besides

the addition of heat traps or an increase in the thickness of the foam insulation, which could

reduce water heater losses enough to yield a significantly large impact on EF. Thus,

EE-RM-97-900 COMMENT 38TT
28

WATSIM's default feed-through losses were concluded to be the likely cause for its low EF

estimates. EPRI confirmed that WATSIM's feed-through loss estimates were indeed too high,

although no indication was given as to the magnitude of the error24.

New simulations were conducted after reducing WATSIM's feed-through loss

estimates to those predicted by TANK. Lower feed-through losses were realized by lowering

the natural convection UA values at the supply and draw lines and by adding 1/8" pipe

insulation for modeling purposes only. By using the same initial baseline characteristics as

listed previously with the exception of a UA value of 0.185 Btu/hr-°F rather than 0.578

Btu/hr'°F, for natural convection feed-through losses, a 0.830 EF was predicted. Because the

EF estimate was still 0.030 points lower than the target value of 0.860 EF, the thickness of the

foam insulation was increased from 1 to '/2 in. (2.5 to 3.8 cm). An 0.858 EF was achieved as

a result of making this change. Thus, the typical existing baseline model as simulated by

WATSIM was able to achieve the minimum allowable NAECA efficiency of 0.86 EF through

the use of 1 /2 in. (3.8 cm) of foam insulation.

Table 8 describes the physical details of the typical existing baseline model electric

water heater used in this analysis. These values describe the water heater in engineering terms

for use in the WATSIM simulation model.

Table 8. Electric Water Heater Existing Baseline Model Characteristics*

Descriptive parameter Value

tank: diameter 15.8 in. (40.1 cm)

height 54.5 in. (138.4 cm)

wall thickness 0.063 in. (0.16 cm)

wall conductivity 0.40 BTU/ftmin- F (41.5 W/m-K)

support ring conductivity 0.40 BTU/ftmin-°F (41.5 W/m-K)

height of concave bottom dome 1.5 in. (3.8 cm)

heat transfer coefficient for tank wall film 20.0 BTU/hr-ft2 -F (113.5 W/m2 K)

tank insulation - thickness top: 1.5 in. (3.8 cm)

side: 1.5 in. (3.8 cm)

bottom: 0.75 in. (1.91 cm)

tank insulation - conductivity top: 0.000233 BTU/ft-min- F (0.0242 W/m-K)

side: 0.000233 BTU/ft-min- F (0.0242 W/m-K)

bottom: 0.000333 BTU/ft-min- F (0.0346 W/m-K)

cold water inlet height 7.5 in. (19 cm)

hot water outlet height 54.5 in. (138 cm)

heater elements - height 1: 7.44 in. (18.9 cm)

2: 38.9 in. (98.8 cm)

heater elements - power 1: 4.50 kW

2: .4.50kW

EE-RM-97-900 COMMENT 38TT
29

heater elements - efficiency 1: 100%

2: 100%

thermostats - height 1: 12.0 in. (30.5 cm)

2: 43.7 in. (111 cm)

feed-throughs - height 1: 54.5 in. (138 cm)

2: 54.5 in. (138 cm)

3: 1.56 in. (3.96 cm)

4: 54.5 in. (138 cm)

feed-throughs - conductivity 1: 0.40 BTU/ft-min- °F (41.5 W/m-K)

2: 0.40 BTU/ft-min °F (41.5 W/m-K)

3: 0.0018 BTU/ft-min-°F (0.1869 W/m-K)

4: 0.40 BTU/ft-min °F (41.5 W/m-K)

feed-throughs - insulation thickness 1: 0.12 in. (0.30 cm)

2: 0.12 in. (0.30 cm)

3: 0

4: 0

feed-throughs - orientation I: vertical

2: vertical

3: horizontal

4: vertical

feed-throughs - radius 1: 0.5 in. (1.3 cm)

2: 0.5 in. (1.3 cm)

3: 0.5 in. (1.3 cm)

4: 0.5 in. (1.3 cm)

feed-throughs - length 1: 24.0 in. (61.0 cm)

2: 24.0 in. (61.0 cm)

3: 6.0 in. (15.2 cm)

4: 3.6 in. (9.1 cm)

feed-throughs - wall thickness 1: 0.036 in. (0.091 cm)

2: 0.036 in. (0.091 cm)

3: 0.036 in. (0.091 cm)

4: 0.036 in. (0.091 cm)

feed-throughs - insulation conductivity 1: 0.000233 BTU/ft-min °F (0.024196 W/mrK)

2: 0.000233 BTU/ft-min-°F (0.024196 W/m-K)

3: 0

4: 0

feed-throughs - natural convection pipe loss 1: 0.185 BTU/hr °F

2: 0.185 BTU/hr-°F

3: 0.0

4: 0.0

Note: * Units in the table are consistent with the units used by the WATSIM simulation model.

EE-RM-97-900 COMMENT 38TT
30

Modeling Design Options

As listed in Table 1, there are only four design options that are being considered to

improve the efficiency of electric storage water heaters. Each design option is briefly

discussed below along with how it was modeled with WATSIM. The discussion begins with

the analysis of the baseline model using foam insulation blown with HFC-245fa rather than

HCFC-141b. As noted before this baseline model is referred to as an "analytic" baseline

model.

Analytic Baseline Model. The blowing agent currently utilized by the water heater

industry for foam insulation, HCFC-141b, is scheduled to be phased out by 2003. Because

new energy-efficiency standards are expected to take effect near the phase out date of HCFC141b, the baseline model for this analysis must utilize foam insulation blown with an

acceptable alternative blowing agent. The most likely alternative to replace HCFC-141b

appears to be HFC-245fa. According to published reports, HFC-245fa has a 3.0% higher

conductivity than HCFC-141b. Thus, the conductivity value of the foam insulation in the

existing baseline model listed in Table 8 was increased by 3.0% to a value of 0.000240

Btu/ft-min- F (0.0249 W/m-K) (the conductivity increase was also applied to the feed-through

insulation). In addition, the thickness of the foam insulation surrounding the tank was

increased to 1.55 in. (3.94 cm) to compensate for the increased conductivity of the insulation.

This increase in insulation thickness also resulted in an increase of jacket material. Table 9

summarizes the changes that were made to the insulation conductivity of a typical existing

baseline model with HCFC-141b in order to simulate its performance with HFC-245fa.

Table 9. Electric Water Heater Modeling Differences: Existing vs. Analytic Baseline Model

- Insulation Conductivity*

Baseline Baseline

Descriptive parameter _ __ w/ HFC-141b w/ HFC-245fa

0.000233 BTU/ft-min-°F 0.000240 BTU/ft-min-°F

insulation conductivity (0.02420 W/m-K) (0.024922 W/m-K)

Note: * Units in the table are consistent with the units used by the WATSIM simulation model.

Heat Traps. The heat conducted and convected through the fittings (water pipes,

drain valve, pressure relief valve, and thermostat) accounts for a significant portion of the total

standby loss in a typical residential-size water heater 25. A heat trap is a device or arrangement

of piping that keeps the buoyant hot water from circulating through a piping distribution

system because of natural convection. When there is no draw of hot water, this device

prevents water in the hot water outlet line from getting back into the tank as it cools off; and

prevents hot water in the tank from circulating back out into the cold water inlet line. Thus,

EE-RM-97-900 COMMENT 38TT
31

by containing the hot water in the storage tank, the heat trap minimizes standby loss. These

devices can be integral to the tank design or independently attached to the inlet and outlet

pipes during installation.

Conventional heat traps are currently made in two styles. In the first style, a floating

plastic ball blocks the cold water inlet. The buoyancy of the plastic holds it in place until

water is drawn. The force of water is strong enough to push the ball out of the way as water

enters the tank. The second style is used for the hot water outlet. In this heat trap, the ball is

denser than water, and the weight of the ball seals the outlet until hot water is drawn and the

water pressure lifts it out of the way. A small bypass channel is left for water to escape back

into the inlet line from the tank. This is necessary because after a large draw fills the tank

with cold water, the water expands as it is heated. Other heat trap designs have also been

invented and produced. These include U-shaped pipes26 , flexible seals27, flaps, springs, and

other mechanisms.

For this analysis, heat traps were analyzed as being either metal or plastic. Both types

of heat traps prevent the losses associated with the circulation of hot water into the piping

distribution system.

For purposes of this analysis, metal heat traps are considered to be those devices which

are attached to the inlet and outlet pipes. Plastic heat traps are considered to be those devices

which are integral to the tank design. On the inlet side, the plastic heat trap is part of a plastic

dip tube assembly where the heat trap mechanism resides near the top of the water heater but

within the tank. On the outlet side, the plastic heat trap is part of a heat trap/anode device

where the heat trap mechanism is part of a plastic cartridge enclosed within the steel pipe that

houses the entire heat trap/anode device.

To simulate the performance of heat traps, the UA values for calculating the natural

convection heat transfer losses at the supply and draw lines were lowered by a magnitude of

0.122 Btu/hr-°F28. The above procedure models the heat losses associated with hot water

recirculation. TANK, the simulation tool for the modeling of gas-fired storage heaters,

models both metal and plastic heat traps. Based upon modeling the performance of a 40

gallon (150 liter) gas-fired water heater with TANK, plastic heat traps prevent losses of

approximately 500 Btu/day (530 kJ/day) relative to metal heat traps. To model plastic heat

traps in WATSIM, the conductivity of the insulation surrounding the supply and draw lines

was decreased to achieve the 500 Btu/day (530 kJ/day) savings. Table 10 summarizes the

changes made to the analytic baseline model (with HFC-245fa) in order to simulate the

performance of metal and plastic heat traps.

EE-RM-97-900 COMMENT 38TT
32

Table 10. Electric Water Heater Modeling Differences: Analytic Baseline Model vs. Models

with Metal and Plastic Heat Traps*

with Metal with Plastic Descriptive parameter Analytic Baseline with Metal th ast

Heat Traps Heat Traps

feed-throughs - insulation I 0.000240 BTU/ft-min-°F 0.000240 BTU/ftmin-F 0.000010 BTU/fimin-°F

(0.024922 W/m-K) (0.024922 W/m-K) (0.001308 W/m-K)

0.000240 BTU/ft-min-°F 0.000240 BTU/ft-min-°F 0.000010 BTU/ft-min-°F

conductivity 2: (0.024922 W/m-K) (0.024922 W/m-K) (0.001308 W/m-K)

feed-throughs - natural convection 1: 0.185 BTU/h °F 0.063 BTU/h °F 0.063 BTU/h- °F

pipe loss 2: 0.185 BTU/h-°F 0.063 BTU/h-°F 0.063 BTU/h °F

Note: * Units in the table are consistent with the units used by the WATSIM simulation model.

Increased Jacket Insulation. The jacket (sides and top) of the water heater is

insulated with polyurethane foam or fiberglass. Because polyurethane foam has a lower

thermal conductivity than fiberglass and is cheaper to install in large volume manufacturing, it

is used almost exclusively. Most water heaters on the market today have at least 1-in. (2.5

cm) thick foam insulation, while some manufacturers provide 2- or 3-in. (5.1 or 7.6 cm) thick

insulation, as well. Although increasing the insulation thickness reduces the standby loss, the

increase in the overall diameter of the water heater may pose some installation problems.

There will also be an increase in shipping costs because fewer heaters will fit in a truck.

Because of these potential installation problems, maximum insulation thicknesses were

limited to 21/2 in. (6.4 cm) for this analysis.

Table 11 summarizes the changes made to the analytic baseline model (with HFC245fa) to simulate the performance of an electric water heater insulated with 2- and 22-in.

(5.1 cm and 6.4 cm) of foam insulation.

Table 11. Electric Water Heater Modeling Differences: Analytic Baseline Model vs. Models

w/ 2 & 21/2 in. of foam insulation

with 2 in. of with 2/2 in. of foam Descriptive parameter Analytic Baseline foam insulation insulation

tank insulation - thickness top: 1.55 in. (3.94 cm) 2.00 in. (5.08 cm) 2.50 in. (6.35 cm)

side: 1.55 in. (3.94 cm) 2.00 in. (5.08 cm) 2.50 in. (6.35 cm)

Insulating the Tank Bottom. The bottom of the tank of an electric water heater can

be insulated with polyurethane foam to reduce the standby heat losses. The use of

polyurethane foam insulation underneath the tank bottom is not conventional practice.

Currently, manufacturers might place fiberglass insulation in the space allotted underneath the

bottom of the water heater due to the concaveness of the tank. For this analysis, the height of

the baseline model's concave dome is assumed to be 1 /2 in. (3.8 cm) with 3

A in. (1.9 cm) of

fiberglass insulation stuffed below it.

EE-RM-97-900 COMMENT 38TT
33

In modeling foam insulation for the tank bottom it was assumed that a foamed

"disk/bottom insulation" assembly would be used. WATSIM models the heat transfer through

the bottom of the tank by two separate parallel heat transfer paths - "bottom" and "support

ring". The "bottom" represents the area of the concave dome and the "support ring"

represents the perimeter, which is a continuation of the tank wall below the bottom of the

tank. The "bottom insulation" portion of this assembly fills the domed space underneath the

tank. The "disk" portion is assumed to lie underneath both the support ring and the "bottom

insulation". Although the "disk" portion of this assembly is assumed to be only 1/a in. (3.2

mm) thick, water heater construction practices prevent the support ring from deforming it,

when the tank is filled with water. The adhesive and structural properties of the foam

insulation keep the tank from crushing the bottom insulation. The bottom insulation portion

of the "disk/bottom insulation" assembly reduces the heat losses from the bottom of the tank,

while the disk portion reduces the conduction heat losses through the support ring.

Table 12 summarizes the changes made to the analytic baseline model to simulate the

performance of electric water heaters with bottom insulation. The support ring conductivity is

assumed to be 50% steel and 50% foam insulation. As a result, its conductivity was twice that

of foam insulation.

Table 12. Electric Water Heater Modeling Differences: Analytic Baseline Model vs. Model

with Foamed Bottom Insulation*

Descriptive parameter Analytic Baseline Foamed Bottom Insulation

tank:support ring conductivity 0.40 BTU/ft-min °F (41.54 W/m-K) 0.000472 BTU/ft-min- F (0.0490 W/m-K)

tank insulation - thickness bottom: 0.75 in. (1.91 cm) 1.5 in. (3.8 cm)

tank insulation - conduct.bottom: 0.000333 BTU/ft-min-°F (0.0346 W/m-K) 0.000240 BTU/ft-min- F (0.0249 W/m-K)

*Units in the table are consistent with use by WATSIM.

Plastic Tank. There are at least two methods for constructing plastic water heater

tanks. One method uses a seamless, blow-molded polybutylene inner tank with a filamentwound fiberglass outer tank, similar to the fabrication of tanks for water softeners29. Another

method consists of constructing a thin steel shell with an internal plastic tank. The tank is

fabricated by first constructing the steel exterior, injecting plastic powder within the steel

shell, and then rotating the tank within a furnace, thereby, coating the interior with the plastic.

The steel exterior serves as the primary structural support for the tank. It is approximately 1/16

in. (1.6 mm) thick while the plastic interior, 1/16 in. to 1

/s in. (1.6 mm to 3.2 mm) thick,

provides a non-corrosive surface in addition to some structural support. In both types of

plastic tanks, the lower heat conductivity of the plastic compared to steel reduces the amount

of heat conducted through the tank wall to the insulation. Both of the plastic tank construction

methods enable an improved process of insulating the tank bottom. In typical electric water

heaters utilizing metal tanks, the metal of the tank wall extends below the bottom of the tank

and acts as a support ring. This support ring has direct contact through the bottom jacket with

the floor and provides a path for conduction heat losses to the floor. Since the plastic tanks

EE-RM-97-900 COMMENT 38TT
34

are completely insulated, standby losses from the bottom of the tank are significantly reduced.

The "steel shell/plastic interior" tank was the plastic tank type modeled for this

analysis as it is the least expensive to manufacture. In modeling this plastic tank type with

WATSIM, the tank wall thickness and conductivity were modified to correspond to the plastic

instead of steel. (The conductivity of the plastic/steel composition at the thickness levels

described above is virtually identical to plastic.) In addition, the support ring material was

changed from steel to foam insulation and the bottom insulation was increased to 1 in. (2.5

cm) of foam insulation. Table 13 summarizes the changes made to the analytic baseline

model to simulate the performance of a plastic tank.

Table 13. Electric Water Heater Modeling Differences: Analytic Baseline Model vs. Plastic

Tank*

Descriptive parameter Analytic Baseline Plastic Tank

tank:wall thickness 0.063 in. (0.16 cm) steel 0.0853 in. (0.16 cm)

plastic 0.126 in. (0.32 cm)

wall conductivity 0.40 BTU/ft-min-°F (41.54 W/m-K) 0.0018 BTU/ft-min-°F (0.1869 W/m-K)

support ring conductivity 0.40 BTU/ft-min-°F (41.54 W/m-K) 0.000236 BTU/ft-min °F (0.024507 W/m-K)

tank insulation - thickness bottom: 0.75 in. (1.91 cm) 1.0 in. (2.54 cm)

tank insulation - conduct. bottom: 0.000333 BTU/ft-min-°F (0.0346 W/m-K) 0.000240 BTU/ft-min-°F (0.0249 W/m-K)

Note: * Units in the table are consistent with the units used by the WATSIM simulation model.

Design Option Manufacturer Costs

Manufacturer costs were primarily based upon data provided by GAMA with the

exception of the plastic tank design option, which were provided by Max Minniear. The cost

estimates were based upon the production of a 50 gallon (190 liter) electric water heater were

disaggregated into variable (material, labor, transportation, overhead) and fixed (capital,

product design) costs. Design option variable costs (from GAMA and Mr. Minniear) and

fixed costs (from GAMA) were provided as a per unit cost and expressed as an incremental

increase over the baseline design. The plastic tank design option fixed costs were provided as

the "lump sum" amount required to convert the baseline production to the new design and the

"lump sum" amount was converted to a per unit cost by amortizing it over a five year period

and dividing it by Mr. Minniear's assumed baseline model production volume of 40,000 units

per year.

EE-RM-97-900 COMMENT 38TT
35

Existing Baseline Model. GAMA's existing baseline model cost estimates were

based upon a water heater with 1I2 in. (3.8 cm) of foamed jacket insulation using HCFC-141 b

as a blowing agent. For the other levels of insulation, the amount and cost of materials

associated with varying thicknesses of HCFC-141b foam insulation were developed. Thus,

the material costs associated with a particular level of insulation could easily be determined by

either subtracting from or adding to GAMA's baseline costs. Table 14 summarizes the

material costs associated with varying levels of foam insulation blown with HCFC-141 b. The

material costs of HCFC-141b foam insulation ($1/lb or $2.2/kg) and sheet metal ($0.30/lb or

$0.66/kg) were based on estimates by Mr. Minniear 30 .

Table 14. Existing Electric Water Heater Material Costs Associated with varying thicknesses

of HCFC-141b Foam Insulation

Polyurethane Foam 141b Jacket Sheet Metal Misc Total

thickness volume' weight 2 cost 3 area thickness weight' cost 5 cost 6 cost

in. (cm) ft' (m3) lb (k) ft 2 (m2) ft 3 (m3) lb (kg)

1.0(2.5) 1.83 (0.05) 3.65 (1.66) $3.65 23.99(2.23) 0.038(0.001) 18.57(8.42) $5.57 $0.00 $9.23

1.5(3.8) 2.84(0.08) 5.68(2.58) $5.68 25.66(2.38) 0.041(0.001) 19.87(9.01) $5.96 $0.00 $11.64

2.0(5.1) 3.92(0.11) 7.84(3.56) $7.84 27.37(2.54) 0.043(0.001) 21.19(9.61) $6.35 $5.67 $19.86

2.5(6.4) 5.07(0.14) 10.14(4.60) $10.14 29.12(2.71) 0.046(0.001) 22.54(10.22) $6.76 $8.04 $24.94

3.0(7.6) 6.29(0.18) 12.59(5.71) $12.59 30.90(2.87) 0.049(0.001) 23.92(10.85) $7.18 $11.59 $31.35

50 gallon (190 liter) tank dimensions: diameter = 15.8 in. (40.1 cm), length = 54.5 in. (138.4 cm), dome height = 1.5 in. (3.8 cm)

2 Foam density = 2 Ib/ft3 (32 kg/m')

Foam cost= $1/lb ($2.2/kg)

Sheet metal density = 489 Ib/ft' (7833 kg/m3

)

Sheet metal cost = $0.30/lb ($0.66/kg)

6 Miscellaneous cost includes additional cost for dams to contain the insulation in a larger cavity during foaming.

Analytic Baseline Model. In order to convert the baseline manufacturer costs

associated with foam insulation blown with HCFC-141b to that blown with HFC-245fa, the

amount and cost of materials associated with varying thicknesses of HFC-245fa foam

insulation were developed. Thus, the material costs associated with a particular level of HFC245fa insulation could easily be determined by adding to the baseline costs associated with a

comparable level of HCFC-141b foam insulation. Table 16 summarizes the material costs

associated with varying levels of HFC-245fa foam insulation. The material costs of HFC245fa foam insulation ($1.32/lb or $2.9/kg) were based on estimates by Allied Signal31. Table

15 shows the calculation of the total foam cost for HFC-141b and HFC-245fa foam

insulation, based on the component cost estimates.

EE-RM-97-900 COMMENT 38TT
36

Table 15. Foam Components Cost Estimate

Foam Components Fraction Component Total Cost Total Cost

Cost (141b) (245fa)

% $/lb $/lb $/lb

blowing agent (141b) 13.00% $1.50 $0.20

blowing agent (245fa) 13.00% $4.00 - $0.52

isocyanurate 51.00% $0.75 $0.38 $0.38

polyols 31.00% $0.65 $0.20 $0.20

catalysts, refractants, etc. 5.00% $4.50 $0.23 $0.23

Total 100.00% $_1.00 $1.32

Table 16. Analytic Electric Water Heater Material Costs Associated with varying thicknesses

of HFC-245fa Foam Insulation

Polyurethane Foam 245fa Jacket Sheet Metal i Misc Total

thickness' volume 2 weights cost4 area thickness' weight 5 cost' cost 7 cost

in. (cm) ft 3 (m3

) lb (kg) (m2) ft l (m ) lb (kg)

1.0(2.5) 1.83(0.05) 3.65(1.66) $4.82 23.99(2.23) 0.038(0.001) 18.57(8.42) $5.57 $0.00 $10.39

1.55(3.94) 2.95(0.08) 5.90(2.68) $7.78 25.84(2.40) 0.041(0.001) 20.00(9.07) $6.00 $0.00 $13.78

2.0 (5.1) 3.92 (0.11) 7.84 (3.56) $10.35 27.37 (2.54) 0.043 (0.001) 21.19(9.61) $6.35 $5.67 $22.37

2.5 (6.4) 5.07 (0.14) 10.14 (4.60) $13.39 29.12 (2.71) 0.046(0.001) 22.54 (10.22) $6.76 $8.04 $28.19

3.0 (7.6) 6.29 (0.18) 12.59 (5.71) $16.61 i 30.90 (2.87) 0.049 (0.001) 23.92 (10.85) $7.18 $11.59 $35.38

'Thickness increased due to increased conductivity of 245fa relative to 141b.

250 gallon (190 liter) tank dimensions: diameter = 15.8 in. (40.1 cm), length = 54.5 in. (138.4 cm), dome height = 1.5 in. (3.8 cm)

3 Foam density = 2 Ib/ft3 (32 kg/m')

4Foam cost = $1.32/lb ($2.9/kg)

5 Sheet metal density = 489 Ib/ft3 (7833 kg/m')

6 Sheet metal cost = $0.30/lb ($0.66/kg)

7 Miscellaneous cost includes additional cost for dams to contain the insulation in a larger cavity during foaming.

As noted in Table 16, the actual thickness level for 1.5 in. (3.8 cm) of HFC-245fa

foam insulation was assumed to be slightly greater than that for HCFC-141b foam insulation

due to HFC-245fa's higher conductivity. For this analysis it was assumed that manufacturers

would retain the same level of insulation thermal resistance for their baseline model when

switching from HCFC-141b to HFC-245fa foam insulation.

Table 17 presents the manufacturer cost estimates for a 50 gallon (190 liter) electric

water heater with 1 /2 in. (3.8 cm) of HCFC-141b foam insulation and the costs associated

with the same baseline model foamed with HFC-245fa insulation. The material costs for the

HCFC-141b baseline model were adjusted upward by the difference in material costs ($2.14)

calculated between the HCFC-141b and HFC-245fa models.

EE-RM-97-900 COMMENT 38TT
37

Table 17. Electric Water Heater Baseline Model with HCFC-141b and HFC-245fa:

Manufacturer Costs

Variable Costs (per unit) Fixed Costs (per unit) Total

Product Mfg

Design Material Labor Overhead Total Capital Design Total Cost

Baseline w/141b- 1.5 in (3.8 cm) $62.16 $12.41 $50.99 $125.56 $0.00 $0.0 0.00 $125.56

Baselinew/245fa- 1.55 in (3.94 cm) $64.30 $12.41 $50.99 $127.70 $00.00 $.00 $0.00 $127.70

Heat Traps. Manufacturer costs for metal and plastic heat traps were based upon data

provided by GAMA. GAMA's data did not provide separate costs for metal and plastic heat

traps. Data from the heat trap manufacturer Perfection, Inc.32 was used as a reference. Metal

heat trap material costs for both the supply and draw lines were based on a %-in. (1.9 cm) by

3-in. (7.6 cm) pipe nipple assembly design. Plastic heat trap material costs for the supply line

were based on a plastic drop-in-tube design while those for the draw line were based on a

plastic cartridge heat trap design within a combined outlet and anode rod assembly. Table 18

summarizes the incremental manufacturer costs for incorporating metal and plastic heat traps

into an electric water heater. GAMA did not disagregate the capital cost and the product

design cost but provided a total fixed cost. The costs reflect the addition of heat traps to both

the supply and draw lines.

Table 18. Heat Traps for Analytic Electric Water Heaters: Incremental Manufacturer Costs

|Incremental Variable Costs (per unit) Incremental Fixed Costs (per unit) j Total

Product Incremental

Design IMaterial Labor Overhead Total Capital Design Total ! Mfg Cost

Heat Traps (metal) $2.59 $0.20 $0.83 $3.62 $0.00 $0.00 $0.39 $4.01

Heat Traps (plastic) \ $2.59 $0.20 $0.83 $3.62 $0.00 $0.00 $0.39 $4.01

Note: 1) Perfection Inc.'s data was almost identical for both types ($3.00 for plastic and $2.95 for metal heat traps); 2) Note that GAMA's

heat trap variable costs are different for electric water heaters and gas-fired water heaters.

Increased Jacket Insulation. Since the analytic baseline model for the Engineering

Analysis assumes foam insulation based on HFC-245fa, manufacturer cost estimates for

increases in the jacket insulation were based upon insulation blown with HFC-245fa. All

foam cost data were based on information provided by Allied Signal. As presented earlier,

Table 14 depicted the material costs for varying levels of HFC-245fa foam insulation. GAMA

provided variable cost and fixed cost data for jacket insulation increases from a baseline level

of 1.5 in. (3.81 cm) to a thickness of 2.0 in. (5.1 cm) only. In order to generate variable cost

and fixed cost data for the next level of insulation, the data provided by M. Minniear was used

to calculate ratios of variable and fixed cost for 2" insulation to 2.5" insulation. GAMA's

costs for 2.0 in. (5.1 cm) insulation modified for 245fa blowing agent, were multiplied by

those ratios to approximate the variable and fixed costs for 2.5 in. (6.4 cm) of insulation.

Table 18 summarizes the incremental manufacturer costs for jacket insulation increases from a

baseline level of 1.5 in. (3.81 cm) to a thickness of 2.0 in. (5.1 cm) and 2.5 in. (6.4 cm) (using

EE-RM-97-900 COMMENT 38TT
38

material cost provided in Table 16). As stated earlier, insulation thicknesses were limited to

2/2 in. (6.4 cm) due to installation and shipping concerns.

Table 19. Increased Jacket Insulation for Analytic Electric Water Heaters: Incremental

Manufacturer Costs

Incr. Variable Cost (per unit) Incr. Fixed Costs (per unit) Total

Product Incremental

Design Material Labor Overhead Total Capital Design Total MfgCost

Incr. Insulation - 2.0 in (5.1 cm) $8.59 $0.51 $3.66 $12.76 $0.00 $0.73 $0.73 $13.49

Incr. Insulation - 2.5 in (6.4 cm) $14.41 $1.02 $7.32 $22.75 $0.00 $1.02 $1.02 $23.77

Insulating the Tank Bottom. Manufacturer costs for insulating the tank bottom were

based on data from GAMA, which included total incremental variable cost and total fixed cost

only. Table 20 summarizes the incremental manufacturing costs for insulating the tank

bottom. The modeling of this design option is based on the following considerations: The

bottom insulation is assumed to fill the entire space covered by the concave dome. Since the

bottom insulation also consists of an 1/s-in. (3.2 mm) foamed disk which the water heater

"stands" on, the overall height of the water heater is increased by 1/8 of an in. (3.2 mm). It is

important to note, that at this time no explanation of the design assumptions associated with

insulating the tank bottom was provided by GAMA. Other sources (Max Minniear and

Eugene West), provided an incremental total cost almost a magnitude lower than GAMA's.

For comparison, Mr. Minniear's total manufacturing cost estimate is $4.25 and Mr. West's

estimate for material cost only is $0.85.

Table 20. Insulating the Tank Bottom for Analytic Electric Water Heaters: Incremental

Manufacturing Costs

i Incremental Variable Costs (per unit) lIncremental Fixed Costs (per unit): Total

Product Incremental

Design I Material Labor Overhead Total Capital Design Total MfgCost

Insulate Tank Bottom ' $0.00 $0.00 $0.00 $26.98 i $0.00 $0.00 $3.39 $30.37

Plastic Tank. Manufacturer costs for a plastic tank electric storage water heater

design were based on data provided by Mr. Minniear. The plastic tank design is based on the

"steel shell/ plastic interior" tank type discussed earlier and assumes a tank wall thickness of

0.20 in. (5.1 mm). Table 21 summarizes the incremental manufacturer costs for switching

from a metal tank to a plastic tank design.

EE-RM-97-900 COMMENT 38TT
39

Table 21. Plastic Tank Design for Electric Water Heaters: Incremental Manufacturer Costs

Incremental Variable Costs (per unit) Incremental Fixed Costs (per unit) Total

Product Incremental

Design Material Labor Overhead Total Capital Design Total MfgCost

Plastic Tank $5.25 $0.80 $3.20 $9.25 l $15.00 $3.00 $18.00 $27.25

Design Option Retail Prices

For purposes of this analysis, the retail price is considered to be the cost to the

consumer of only the water heating equipment. The cost to the consumer of installing the

water heater (i.e., the installation cost) is not considered to be part of the retail price and is

discussed later.

The retail price for a baseline 50-gallon (190 liter) electric storage water heater (with

HCFC-141 b foam insulation) was determined by contacting various plumbing contractors and

large retail chains. Since the price of a water heater is a function of the length of the

manufacturer's warranty, only water heaters warrantied for 5 years were considered as

baseline models. The 5 year warranty is the shortest warranty period offered by water heater

manufacturers (although a 1 year warranty is offered in special cases) and is typically reserved

for those models which are produced in large volumes (i.e., baseline models). A longer

warranty time period, in addition to raising the price, may indicate the presence of design

feature not normally found in baseline models. Table 22 provides the list of retail prices used

to develope the retail price of the baseline model. For each price listed, the source is also

provided. All data presented in Table 22 are from the LBNL Water Heater Database33.

Table 22. 50-Gallon (190 liter) Electric Storage Water Heater Retail Prices

Source Manufacturer Brand Model Retail

Denver, CO State Industries Reliance 5-52-20RT $128.00

Dale City, VA American Water Heaters Craftsman $128.00

Atlanta, GA American Water Heaters PROLine E52-50R-045DV $129.00

Atlanta, GA American Water Heaters PROLine E52-50R-045DV $135.00

Stockbridge, GA American Water Heaters Envirotemp E52-50R-045DV $138.00

Marieeta, GA American Water Heaters Envirotemp E52-50R-045DV $138.00

Charlotte, NC American Water Heaters More-Flo E52-50R-045DV $141.00

Dallas, TX State Industries Reliance 5-52-20RT $146.00

West Allis, WI American Water Heaters American $147.00

Chicago, IL American Water Heaters More-Flo E52-50R-045DV $148.00

Minneapolis, MN American Water Heaters More-Flo E52-50R-045DV $148.00

SW Jackson, MS American Water Heaters American E52-50R-045DV $149.00

Lexington, KY American Water Heaters American E52-50R-045DV $149.00

New Orleans, LA American Water Heaters American E52-50R-045DV $149.00

Jacksonville, FL A.O. Smith Energy Saver EES-52 $152.00

Nashville, TN American Water Heaters American E52-50R-045DV $157.00

EE-RM-97-900 COMMENT 38TT
40

Source Manufacturer Brand Model Retail

St. Louis, MO American Water Heaters American E52-50R-045DV $160.00

Kilgore, TX A.O. Smith Energy Saver FSG-50 $163.00

Salt Lake City, UT American Water Heaters American E52-50R-045DV $168.00

Denver, CO State Industries Reliance 5-52-20RT $168.00

Reno, NV American Water Heaters American E52-50R-045DV $168.00

Harrisonburg, VA State Industries SCD-552-2ORT $170.00

Richmond, CA Sears/State Industries Kenmore 31256 $170.00

Charlotte, NC American Water Heaters $171.00

Sacramento, CA American Water Heaters American E52-50R-045DV $172.00

Seattle, WA State Industries Reliance 5-52-20RT $175.00

Nashville, TN American Water Heaters American E52-50R-045DV $177.00

Winchester, VA Rheem Rheem 81V52D $178.00

Phoenix, AZ State Industries Reliance 5-52-20RT $179.00

Las Vegas, NV State Industries Reliance 5-52-WORT $179.00

Fredericksburg, VA State Industries CD5-52-2ORT $180.00

Corpus Christy, TX Rheem Standard 81V52D $180.00

Boise, ID State Industries Reliance 5-52-2KRT $183.00

Boise, ID State Industries Reliance 5-52-20RT $184.00

Oklahoma City, OK State Industries Reliance 5-52-20RT $187.00

St. Louis, MO American Water Heaters American E52-50R-045DV $189.00

Boston, MA State Industries Powermiser 5 31256 $190.00

Indianapolis, IN State Industries CD6-52-20RT $197.00

Salt Lake City, UT American Water Heaters American E52-50R-045DV $198.00

Boston, MA State Industries Powermiser 5 31256 $200.00

Livermore, CA Sears/State Industries Kenmore $200.00

Charlottesville, VA Rheem Ruud PE52 $208.00

Boise, ID State Industries Reliance 5-52-2KRT $208.00

Berkeley, CA Rheem Rheem 81V52D $227.00

Anchorage, AK Bradford White $231.00

Tampa, FL Rheem Standard 81V50D $234.00

Berkeley, CA Rheem Rheem 81SV52D $239.00

Boston, MA State Industries Anniv. Series 10 $250.00

Bristow, VA Rheem Rheem 81V52D $282.00

Boise, ID State Industries Reliance 5-52-2KRT $297.00

Average Retail Cost $178.88

As listed in Table 22, the average retail price for a baseline 50 gallon (190 liter)

electric storage water heater was $178.88 (without taxes). As presented earlier, the

manufacturer cost of any existing baseline water heater is $125.56. Using the average national

value for taxes of 5.20% (developed by A.D.L, 1998), yields a retail price of $188.18.

Dividing the retail price ($188.18) by the manufacturer cost ($125.56) it yields a manufacturer

cost-to-retail price markup of 1.50 (an exact value of 1.49874 is used as a multiplier).

EE-RM-97-900 COMMENT 38TT
41

The baseline manufacturer cost-to-retail price markup was assumed constant for all

design options considered for this analysis. Thus, the retail price for any modified design was

simply determined by multiplying the manufacturer cost by the derived markup of 1.50.

Installation and Maintenance Costs

The installation cost is the cost to the consumer of installing the water heater and is not

considered part of the retail price. The cost of installation covers all labor and material costs

associated with the simple replacement of an existing water heater. Delivery, removal, and

permit fees are also included.

LBNL collected data to establish the installation cost of a 50 gallon (190 liter) baseline

electric storage water heater from the same sources that the retail price data was obtained.

Table 23 lists the installation costs for the water heater models. The average installation cost

was $160.73. None of the design options considered for this analysis increased the installation

cost of a baseline electric storage water heater. All data presented in Table 23 are from the

LBNL Water Heater Database34.

Table 23. 50-Gallon (190 liter) Electric Storage Water Heater Installation Costs

Source Manufacturer Brand Model Installation

Berkeley, CA Rheem Rheem 81SV52D $65.00

Berkeley, CA Rheem Rheem 81V52D $65.00

Boise, ID State Industries Reliance 5-52-2KRT $114.00

Boise, ID State Industries Reliance 5-52-2KRT $114.00

Boise, ID State Industries Reliance 5-52-2KRT $114.00

Boise, ID State Industries Reliance 5-52-2KRT $114.00

Stockbridge, GA American Water Heaters Envirotemp E52-50R-045DV $119.00

Salt Lake City, UT American Water Heaters American E52-50R-045DV $125.00

Salt Lake City, UT American Water Heaters American E52-50R-045DV $125.00

Denver, CO State Industries Reliance 5-52-20RT $130.00

Denver, CO State Industries Reliance 5-52-20RT $130.00

SW Jackson, MS American Water Heaters American E52-50R-045DV $135.00

Phoenix, AZ State Industries Reliance 5-52-20RT $136.00

Atlanta, GA American Water Heaters PROLine E52-50R-045DV $142.00

Nashville, TN American Water Heaters American E52-50R-045DV $145.00

Nashville, TN American Water Heaters American E52-50R-045DV $145.00

Charlotte, NC American Water Heaters More-Flo E52-50R-045DV $145.00

Marieeta, GA American Water Heaters Envirotemp E52-50R-045DV $149.00

Reno, NV American Water Heaters American E52-50R-045DV $154.00

Charlotte, NC American Water Heaters $155.00

Dallas, TX State Industries Reliance 5-52-20RT $155.00

West Allis, WI American Water Heaters American $159.00

St. Louis, MO American Water Heaters American E52-50R-045DV $160.00

St. Louis, MO American Water Heaters American E52-50R-045DV $160.00

Dale City, VA American Water Heaters Craftsman $169.00

EE-RM-97-900 COMMENT 38TT
42

Source Manufacturer Brand Model Installation

Springfield, VA Rheem Rheem 81V52D $170.00

Springfield, VA A.O. Smith A.O. Smith EES52 $170.00

Las Vegas, NV State Industries Reliance 5-52-20RT $170.00

Richmond, CA Sears/State Industries Kenmore 31256 $174.00

Tampa, FL Rheem Standard 81V50D $175.00

Oklahoma City, OK State Industries Reliance 5-52-20RT $180.00

Lexington, KY American Water Heaters American E52-50R-045DV $200.00

Chicago, IL American Water Heaters More-Flo E52-50R-045DV $209.00

Sacramento, CA American Water Heaters American E52-50R-045DV $210.00

Boston, MA State Industries Anniv. Series 10 $220.00

Boston, MA State Industries Powermiser 5 31256 $220.00

Boston, MA State Industries Powermiser 5 31256 $220.00

New Orleans, LA American Water Heaters American E52-50R-045DV $225.00

Seattle, WA State Industries Reliance 5-52-20RT $231.00

Atlanta, GA American Water Heaters PROLine E52-50R-045DV $234.00

Minneapolis, MN American Water Heaters More-Flo E52-50R-045DV $258.00

Average Installation Cost $160.73

Information gathered to date suggests that there is virtually no maintenance of

residential electric water heaters, although manufacturers recommend they be drained and

flushed annually to minimize deposition of sediment, maintain operating efficiency and

prolong equipment life. Thus, maintenance costs were not developed for the baseline model.

The design options considered for this analysis were assumed not to increase the maintenance

cost of electric water heaters.

Cost-Efficiency Data

The results of the design option analysis for 50 gallon (190 liter) electric storage water

heaters are presented in Table 24. Included in the cost-efficiency table are the following:

disaggregated manufacturer costs, retail prices, installation costs, maintenance costs, energy

factor, energy use, and payback periods. Design options were added incrementally to the

baseline model in order of shortest payback period. The payback period for each set of design

options was calculated relative to the baseline design according to the following relationship:

ACC ARC+ AIC

PA YBA CK = -= A OC AEC+ AMC

where;

PAYBACK = payback period (years),

ACC = change in consumer cost relative to baseline, ($),

AOC = change in operating cost relative to baseline, ($/year),

ARC = change in retail cost relative to baseline, ($),

AIC = change in installation cost relative to baseline, ($),

AEC = change in energy cost relative to baseline, and ($/year),

EE-RM-97-900 COMMENT 38TT
43

AMC = change in annualized maintenance cost relative to baseline,

($/year).

The existing baseline design with HCFC-141b foam insulation is presented in Table 24

to show the manufacturer cost and retail price differences between the baseline designs with

HCFC-141b and HFC-245fa. For purposes of this analysis, the cost effectiveness of all design

options were evaluated relative to the analytic baseline design with HFC-245fa. Energy costs

were from national average energy prices for the year 2003 from the 1998 Annual Energy

Outlook 35.

Metal heat traps are not included in the cost/efficiency table because plastic heat traps

are more cost effective. The highest EF attainable is 0.908 which can be achieved through the

use of plastic heat traps, 2'/2 in. (6.4 cm) of jacket insulation, and a plastic tank. The payback

period of this design is just over 4 years and there are 238 kWh/yr energy savings. Electric

water heaters incorporating plastic heat traps, 2.5 in. of insulation and tank bottom insulation

have a payback of 4.6 years. This design saves 233 kWh/yr in electricity.

As described earlier in this report, the EF and other parameters of the water heater,

such as the RE, were determined from output generated by the WATSIM simulation model

and the DOE test procedure equations. It is interesting to note that the recovery efficiencies

calculated in this manner for the baseline model and design options and reported in Table 24

are less than the 98% RE default permitted by the DOE test procedure.

Figure 1 graphically depicts the relationship between both increased consumer cost and

increased operating cost versus EF.

EE-RM-97-900 COMMENT 38TT
44

Table 24. Cost-Efficiency Table for 50 gallon (190 liter) Electric Storage Water Heaters

Incremental Variable Costs '2 Incremental Fixed Costs Total Energy Use Payback

Design Total Product Total Mfg Retail Install. Maint. Energy Recov. UA Daily Yearly Period4

No. Design Options Mat'l Labor Overhd Var. Capita Design Fixed Cost Price' Cost' Cost' Factor Eff. kWh/day kWh/yr years

0 Existing Baseline (l4b)- 1.5"(3.8 $62.16 $12.41 $50.99 $125.56 $0.00 $0.00 $. $125.56 $188.18 $160.73 $0.00 0.858 96.69% 3.64 13.60 4965 NA cm)'

Oa Analytic Baseline (245fa)-1.5 $0.00 $0.00 $2.14 $0.00 $0.00 $0.00 $127.70$191.39 $160.73 $0.00 0.858 96.69% 3.64 13.60 4965 NA (3.8 cm)

I Oa + Heat Traps (plastic) $2.59 $0.20 $0.83 $3.62 $0.00 $0.39 $0.39 $131.71 $197.40 $160.73 $0.00 0.876 97.02% 3.06 13.36 4875 0.85

2 + Incr. Insulation to 2" (5.1 cm) $8.59 $0.51 $3.66 $12.76 $0.00 $0.73 $0.73 $145.20 $217.62 $160.73 $0.00 0.890 97.17% 2.62 13.17 4805 2.08

3 I + Incr. Insulation to 2.5" (6.4 cm) $14.41 $1.02 $7.32 $22.75 $0.0 $1.02 $1.02 $155.48 $233.02 $160.73 $0.00 0.901 97.27% 2.29 13.03 4755 2.52

4 3 + Plastic Tank 4 $5.25 $0.80 $3.20 $9.25 $15.00 $3.00 $18.00 $182.73 $273.86 $160.73 $0.00 0.908 97.03% 2.06 12.95 4727 4.40

5 3 + Insulate Bottom $0.00 $0.00 $0.00 $26.98 $0.00 $0.00 $3.39 $185.85 $278.54 $160.73 $0.00 0.908 97.27% 2.13 12.97 4732 4.76

All costs and prices in 1998$.

2 Incremental variable and fixed costs are per unit costs.

'For the Baseline Model with HCFC-141b, the TOTAL variable costs are provided.

4 Annual operating cost for Payback Period calculation established with an electricity price of 0.0787 $/kWh in 1998$.

Retail Prices are calculated based on the Manufacturer to Retail Markup of 1.49874.

EE-RM-97-900 COMMENT 38TT
45

$450 $395

w----- Consumer Cost

5

a $425 ! ...... Operating Cost $390

( $400 $385 _

E * 3 / c;

$375 $380

C

$350 -a $375 0

E. 4 5

$325 - - $370

0.85 0.86 0.87 0.88 0.89 0.90 0.91 0.92

Energy Factor

Figure 1. 50 gallon (190 liter) Electric Storage Water Heaters: Total Consumer Cost and

Operating Cost vs. Energy Factor

GAS-FIRED WATER HEATERS

The Engineering Analysis models the design options for gas-fired water heaters using

TANK, a computer simulation model for water heaters developed by Battelle for GRI. A 40

gallon (150 liter) nominal volume gas-fired water heater was used as the baseline model for this

analysis.

Existing Typical Baseline model

In using TANK to establish the baseline model, the goal was to establish the

characteristics of a 40 gallon (150 liter) baseline gas-fired water heater with HCFC-141b foam

insulation which would yield a 0.54 EF (the minimum EF allowed by NAECA) and a RE close to

76%.

From information in GAMA's directory of certified water heaters and product literature

from various manufacturers, it was determined that models of 40 gallon (150 liter) gas-fired

water heaters achieved 0.54 EFs through the use of 1 in. (2.5 cm) foam insulation only (heat traps

were not necessary). The input rating varied between 34,000 and 40,000 Btu/hr (10,000 to

11,700 W). As a result of preliminary simulation work, it was determined that EFs close to 0.54

could only be achieved with input ratings of 40,000 Btu/hr (11,700 W) and flue diameters of 4 in.

EE-RM-97-900 COMMENT 38TT
46

(10 cm). Thus, the baseline model was established with the following "general" characteristics:

input rating of 40,000 Btu/hr (11,700 W), flue diameter of 4 in. (10.2 cm), 1 in. (2.5 cm) of foam

insulation, and no heat traps.

In developing the baseline model, Battelle was consulted because it had conducted

simulations to characterize baseline gas-fired water heaters. Battelle's initial results were

presented to a meeting of GRI's Water Heater Technical Advisory Group (TAG) in November,

1997 and are depicted in Table 25. Of Battelle's baseline characteristics, the input rating (39,630

Btu/hr (11614 W)), insulation thickness (0.981 in. (2.492 cm)), flue diameter (4 in. (10.2 cm)),

and heat traps (none) are virtually identical to the "general" baseline characteristics stated above.

With regard to the insulation thickness, Battelle measurements revealed that insulation

thicknesses in gas-fired water heaters are actually slightly less than the nominal values (e.g., a "1

in." nominal thickness is actually 0.981 in. (2.492 cm)).

Table 25. Battelle Baseline Model Characteristics as presented at November 1997 GRI TAG

meeting

Parameter Value

Input Rating 39630 Btu/hr (11614 W)

Pilot Input 400 Btu/hr (117 W) -

Excess Combustion Air (%) 39.0

Pressurized Tank Dimensions

Inside Diameter 15.84 in. (40.23 cm)

Steel Wall Thickness 0.08 in. (0.20 cm)

Height 47.6 in. (120.9 cm)

Volume 38.0 gallons (143.8 liter)

Jacket Description

Foam insulation thickness 0.981 in. (2.492 cm)

Sheet metal thickness 0.019 in. (0.483 mm)

Thermal conductivity of foamed assembly 0.0155 Btu/hr-ft °F (0.0268 W/m-K)

Off-cycle pressure loss coefficient 13.0042

Flue baffle effectiveness multiplier 1.896

Flue diameter 4.0 in. (10.2 cm)

Recovery efficiency (RE) (%) 75.0

Energy factor (EF) 0.54

EE-RM-97-900 COMMENT 38TT
47

From discussions with Battelle3 6, it was learned that three input variables, the excess

combustion air, the flue baffle effectiveness multiplier, and the off-cycle pressure loss

coefficient, were varied in an attempt to achieve both a 0.54 EF and a 76% RE. In varying the

above three input variables, Battelle was able to arrive at an EF of 0.54 but a RE of only 75%.

Because a 76% RE was not achieved with Battelle's baseline specifications, additional

simulations were conducted to try to develop a 0.54 EF and 76% RE baseline. Feed-through

losses were kept the same for electric and gas-fired water heaters. In addition, the same

conductivities were specified for the jacket insulation for both the existing baseline gas and

electric water heaters.

The excess combustion air, flue baffle effectiveness multiplier, and the off-cycle pressure

loss coefficient are not independent of each other and cannot be varied independently to arrive at

the desired EF and RE values. The off-cycle pressure loss coefficient can be expressed as a

function of both the flue baffle effectiveness multiplier and excess combustion air. In turn, the

EF and RE can also be expressed as functions of flue baffle effectiveness multiplier and excess

combustion air (for a given set of input characteristics). Figure 2 depicts the variation of EF and

RE with excess combustion air and flue baffle effectiveness multiplier. As Figure 2

demonstrates, 0.54 EFs and 76% REs occur at different sets of excess combustion air and flue

baffle effectiveness multiplier values.

4.0

EF

3.5 ---- RE _-- EF=0.56

.

3

.

0 RE=78- ~ - = _ _ _EF=0.5 5

1.5 RE=78%- - - / -5 25

RE=77O/o- - W O W. EF=0.54

_ 20 w u RE=76%0

EF = 0.53

ff 1.5 RE=75%/05

E RE= 74% -/" 1 .0 EF =0.52

0.5

0.0 --

22.5% 25.0%/ 27.5% 30.0%0 32.5% 35.0% 37.5% 40.0°/0 425% 45.0%/ 47.5%

Excess Combustion Air

Figure 2. Energy Factor and Recovery Efficiency vs. Flue Baffle Effectiveness and Excess

Combustion Air

EE-RM-97-900 COMMENT 38TT
48

Based on the above results, other TANK input variables were investigated as a means of

increasing RE (without significantly impacting EF) or decreasing EF (without significantly

impacting RE). Table 26 indicates the TANK input variables which were investigated. The

acceptable range provided for the combustion chamber inner wall thickness, the flue wall

thickness, the flue baffle thickness, the thermostat R-value, the skirt insulation, and the tank,

flue, and flue baffle emissivities were based on what seemed to be reasonable values for these

variables. The off-cycle pressure loss coefficient is not provided in Table 26 as it is dependent

on the flue baffle effectiveness and the excess combustion air and is calculated by TANK.

Table 26. TANK Input Variables: Approximate Impact on EF and RE

TANK Acceptable

Input Variable Default Range Impact on EF and RE

Flue Baffle Effectiveness 1.896 1.2 - 2.0 Increase causes increased EF and RE

Excess Combustion Air 32% 25% - 70% Increase causes decreased EF and RE

Pressure Vessel Wall Thickness - in (cm) 0.08 (0.20) > 0.05 (> 0.13) Decrease causes small RE incr., small EF decr

Combustion Chamber Height - in (cm) 8.5 (21.6) 7.5-9.5 (19.1-24.1) Decrease causes incr'd RE; low impact on EF

Comb. Chamber Inner Wall Thick. - in (cm) 0.04 (0.10) > 0.03 (>0.08) Decrease causes incr'd RE; low impact on EF

Multiplier for Dome-Shaped Comb. Chamber 1.15 1.00 - 1.30 Increase causes incr'd EF and RE; larger RE incr

Flue Wall Thickness - in (cm) 0.08 (0.20) > 0.05 (>0.13) Increase causes small RE incr.; no impact on, EF

Flue Baffle Thickness - in (cm) 0.063 (0.16) > 0.04 (> 0.10) Increase causes incr'd RE; low impact on EF

R-value T'stat Fitting - hrft2- F/Btu (K-m2/W) 0.10 (0.02) 0.05-0.10 (0.01-0.02) Decrease causes small EF decr; no impact on RE

Skirt Insul. Conduct - Btu/hr-ft- "F (W/m2-K) 0.03 (0.05) 0.02-0.04 (0.03-0.07) Increase causes decr'd EF and RE; larger EF deer

Emissivity for Tank, Flue, and Flue Baffle 0.95 < 0.97 Decrease causes decr'd EF & RE; larger RE decr

Starting with a flue baffle effectiveness (2.0) and excess combustion air (40%) that

yielded an EF close to 0.54 and as high an RE as possible, the above input variables were

adjusted in an attempt to increase the RE to 76% without significantly increasing the EF. In

order to realize an EF and RE within a half a percentage point of the desired values, some of the

input variables had to be set beyond their acceptable range. Table 27 provides the values of the

above input variables that were used to arrive at acceptable EF and RE values. Input values in

Table 27 appearing in bold font, the combustion chamber height, the combustion chamber inner

wall thickness, the flue baffle thickness, and the skirt insulation conductivity, were the only

variables set beyond their acceptable limits. Although their limits were exceeded, none went

significantly beyond the acceptable range. This set parameters may not match the physical

characteristics of the actual water heaters, but do allow the simulation model to predict the

expected level of energy consumption, EF and RE.

EE-RM-97-900 COMMENT 38TT
49

Table 27. TANK Input Values providing acceptable EF and RE values

Value Acceptable

Input Variable Used Range

Flue Baffle Effectiveness 2.0 1.2 - 2.0

Excess Combustion Air 42% 25% - 70%

Pressure Vessel Wall Thickness - in. (cm) 0.054 (0.137) > 0.05 (> 0.13)

Combustion Chamber Height - in. (cm) 6.5 (16.5)' 7.5 - 9.5 (19.1 - 24.1)

Comb. Chamb. Inner Wall Thick. - in. (cm) 0.01 (0.025)' > 0.03 (> 0.08)

Multiplier for Dome-Shaped Comb. Chamber 1.25 1.00 - 1.30

Flue Wall Thickness - in. (cm) 0.05 (0.13) > 0.05 (> 0.13)

Flue Baffle Thickness - in. (cm) 0.03 (0.076)' > 0.04 (> 0.10)

R-value for Thermostat Fitting - hrft2 °F/Btu (K-m2/W) 0.05 (0.01) 0.05 - 0.10 (0.01 - 0.02)

Skirt Insulation Conductivity - Btu/hrft- °F (W/m-K) 0.042 (0.073)' 0.02 - 0.04 (0.03 - 0.07)

Emissivity for Tank, Flue, and Flue Baffle 0.95 <0.97

'Value used is outside of acceptable range.

The above input variables yielded a 0.5446 EF and a 75.5% RE. Table 28 summarizes

the primary baseline characteristics. Note that the conductivity of the jacket insulation was

changed from the TANK default value to match that being used in the baseline electric water

heater model. The values in Table 28 describe the water heater in engineering terms used by

TANK.

Table 28. Gas-Fired Water Heater Baseline Model Characteristics

Descriptive parameter Value

Input Rating 40000 Btu/hr (11723 W)

Pilot Input 400 Btu/hr (117 W)

On-cycle power consumption 0.0 W

Off-cycle power consumption 0.0 W

Excess Combustion Air 42.0 (%)

Off-cycle pressure loss coefficient 12.4047

Flue baffle effectiveness multiplier 2.000

Natural Gas - Higher Heating Value 1028 Btu/scf (38302 kJ/m3)

Pressurized Tank Dimensions

Inside Diameter 15.892 in. (40.366 cm)

Steel Wall Thickness 0.054 in. (0.1372 cm)

Height 47.6 in. (120.9 cm)

Volume 38.0 gallons (143.8 liter)

Jacket Description

Foam insulation thickness 0.981 in. (2.492 cm)

Sheet metal thickness 0.019 in. (0.0483 cm)

Thermal conductivity of foamed assembly 0.0140 Btu/hr-ft °F (0.0242 W/m-K)

EE-RM-97-900 COMMENT 38TT
50

Outer Jacket Emissivity 0.92

Flue Description

Internal Diameter 4.00 in. (10.16 cm)

Area Fraction for Upflow 0.066

Flue Wall Thickness 0.050 in. (0.127 cm)

Flue Baffle Emissivity 0.95

Flue Baffle Thickness 0.030 in. (0.0762 cm)

Combustion Chamber Description

Skirt Insulation Thermal Conductivity 0.042 Btu/hr-ft °F (0.073 W/m-K)

Chamber Height 6.5 in. (16.5 cm)

Chamber Inner Wall Thickness 0.010 in. (0.0254 cm)

Flame Radiation View Factor to Skirt 0.2

Distance between Burner and Fire Entrance 4.00 in. (10.16 cm)

Dome Heat Transfer Area Multiplier 1.25

Pipes and Fittings

Heat Traps (0 - none, I - metal, -1 - plastic) 0

Supply and Draw Pipe Inside Diameter 0.785 in. (1.994 cm)

Pressure Relief Valve Exposed Area 18.0 in2 (116.1 cm 2

)

Drain Valve Exposed Area 9.0 in2 (58.1 cm2)

Thermostat Exposed Area 9.0 in2 (58.1 cm2)

Anode Rod Fittings Exposed Area 0.0 in2 (0.0 cm2

)

Volume to Thermostat 4.05 gallons (15.33 liter)

Modeling Design Options

Table 1 shows the seven design options which are being considered to improve the

efficiency of gas-fired storage water heaters. Each design option is briefly discussed below along

with the methodology of how it was analyzed with TANK. TANK determines the pressure loss

coefficient based on the water heater's characteristics. Although the pressure loss coefficient is

primarily dependent on the excess combustion air and the flue baffle effectiveness multiplier,

any water heater characteristic can effect the off-cycle pressure loss coefficient. Thus, before a

TANK simulation run was conducted for a design option, the off-cycle pressure loss coefficient

was determined with TANK based on the characteristics.of the water heater. After the off-cycle

pressure loss coefficient was established, it was specified as one of the water heater's

characteristics and TANK was used to model the water heater's performance. For some design

options, such as heat traps and increased jacket insulation, there was little impact on the off-cycle

pressure loss coefficient but the improved flue baffle design option had a significant effect on the

off-cycle pressure loss coefficient.

The side-arm heater was the only design option not modeled with TANK. Because

TANK is not able to model side-arm heaters, the WHAM energy calculation method was used to

estimate efficiency improvement of this design option.

Analytical Baseline Model. The existing baseline model's HCFC-141b foam insulation

EE-RM-97-900 COMMENT 38TT
51

was replaced with HFC-245fa foam insulation due to the impending phase out of HCFC-141 b in

the year 2003. According to the Bayer report, HFC-245fa has a 3.0% higher conductivity than

HCFC-141b - see Table 4. Thus, the conductivity value of the foam insulation in the baseline

model listed in Table 26 was increased by 3.0% to a value of 0.0144 Btu/hr-ft-°F (0.0249

W/m-K). In addition, the thickness of the foam insulation surrounding the tank was increased

from 0.981 in. (2.492 cm) to 1.00 in. (2.54 cm) to compensate for the insulation's increased

conductivity. This increase in insulation thickness also resulted in an increase of jacket material.

Table 29 summarizes the changes that were made to the existing baseline model with HCFC141b in order to simulate its performance with HFC-245fa.

Table 29. Gas-Fired Water Heater Modeling Differences: Existing Baseline Model vs. Analytic

Baseline Model

Descriptive parameter Existing Baseline Analytic Baseline

Jacket Description

Foam insulation thickness 0.981 in. (2.492 cm) 1.000 in. (2.540 cm)

Thermal conductivity of foamed assembly 0.0140 Btu/hrft-°F (0.0242 W/m-K) 0.0144 Btu/hr-ft-°F (0.0249 W/m-K)

Heat Traps. Metal and plastic heat traps were analyzed for gas-fired storage water

heaters. Both types of heat traps prevent the losses associated with the circulation of hot water

into the plumbing.

To simulate the performance of heat traps using TANK, the input variable designating the

presence of heat traps simply needs to be specified with a value of 1 for metal heat traps or -1 for

plastic heat traps. Table 30 summarizes the changes made to the analytic baseline model in order

to simulate the performance of metal and plastic heat traps.

Table 30. Gas-Fired Water Heater Modeling Differences: Analytic Baseline Model vs. Models

with Metal and Plastic Heat Traps

Descriptive parameer Analytic Baseline with Metal Heat with Plastic Heat Descriptive parameterTrapsTraps Traps Traps

Pipes and Fittings

Heat Traps (0 - none, 1 - metal, -1 - plastic) 0 1 -1.

Increased Jacket Insulation. Most gas-fired water heaters on the market today have at

least 1-in. (2.5 cm) thick polyurethane foam insulation, while some manufacturers provide 2- or

3-in. (5.1 or 7.6 cm) thick insulation, as well. Although increasing the insulation thickness

reduces the standby loss, the increase in the overall diameter of the water heater may pose some

EE-RM-97-900 COMMENT 38TT
52

installation problems. There will also be an increase in shipping costs because fewer heaters will

fit in a truck. Because of these potential installation problems, maximum insulation thicknesses

were limited to 21

/2 in. (6.4 cm) for this analysis.

Table 31 summarizes the changes made to the analytic baseline model to simulate the

performance of a gas-fired water heater insulated with nominal thicknesses of "2-in." (1.981 in.

(5.032 cm)) and "2/2-in." (2.481 in. (6.302 cm)) of foam insulation.

Table 31. Gas-Fired Water Heater Modeling Differences: Analytic Baseline Model vs. Models

w/ 2 & 2/2 nominal in. of foam insulation

with 2 in. of foam with 2/2 in. of foam Descriptive parameter Analytic Baseline . insulation insulation

Jacket Description

Foam insulation thickness 1.000 in. (2.540 cm) 1.981 in. (5.032 cm) 2.481 in. (6.302 cm)

Improved Flue Baffle. The standard flue baffle is a twisted strip of metal inserted into

the flue. It increases the turbulence of flue gases and improves heat transfer to the walls of the

flue. The geometry of the flue baffle can be modified to increase its effectiveness.

A research project funded by GRI reviewed technical literature, manufacturers' literature,

and patents to determine what new technologies are applicable to heat exchangers that involve

flue gases from combustion of natural gas37. The conclusion was that significant increases in the

convective heat transfer coefficient could be achieved with the use of heat transfer enhancement

devices. The study suggested that in some cases, an increase in heat transfer coefficient might be

accompanied by an increase in the pressure drop (due to an increase in the friction factor). The

study identified twisted-tape inserts as a potential heat transfer enhancement device for water

heaters.

Burners in fuel-fired water heaters are placed below the storage tank, with the flue

extending up through the center of the tank to a draft hood. The combustion products enter the

flue tube at a very high temperature (approximately 2300°F (1260 C)) and transfer heat by

convection and radiation to the tube wall, and then by conduction to the water. When a baffle,

such as a flat plate, is inserted in the flue, increased heat transfer occurs from the hot combustion

products to the flue wall. The increase in the heat transfer is even greater when a twisted baffle

tape is inserted in the flueway of a water heater. The twisted tape augments the convective heat

transfer from the flue gases to the wall surfaces. In addition, the hot tape transfers heat to the

water-tube walls by radiation.

EE-RM-97-900 COMMENT 38TT
53

Beckermann and Goldschmidt3 8 investigated experimentally and empirically the effects of

velocity of the flue gases, the twist (i.e., number of turns) of the tape, and the surface emissivities

on the total heat transfer (convection and radiation) in a fuel-fired water heater. They reported

that compared to an empty tube, the flue tube with twisted tape enhances the overall heat transfer

performance by as much as 50%.

An improved flue baffle can increase the RE to about 78-85%, depending on the specific

geometry. At the upper end of the RE range, the water heater would require power venting or

induced draft and corrosion resistant flues for safe operation.

In addition to an increase in RE, improved flue baffles also reduce standby loss. The offcycle standby loss is reduced by the additional restrictions to airflow due to the increased

baffling. But because the enhanced or increased flue baffling increases pressure drop across the

flue, the combustion products may have to be forced through the flue with a fan or blower.

Venting combustion products through a horizontal venting system also requires a fan or blower.

When the blower forces fresh air into the chamber, the configuration is called a forced draft

system. By contrast, when the blower is located in the flue-gas exit, the configuration is called

an induced draft system. In an induced draft system the blower is exposed to hot and potentially

corrosive flue gases and, therefore, should be made of materials that can withstand these

conditions.

Using a fan to force the flue gases through the baffle with either an induced-draft blower

(downstream of the water heater) or a forced-draft blower (upstream of the water heater), can

increase the RE and reduce the off-cycle flue losses. The increased RE resulting from this design

option may necessitate relining or otherwise modifying some venting systems to prevent

corrosion or damage from condensation.

Several manufacturers currently make water heaters with induced-draft blowers.

However, this feature is usually added to allow sidewall venting and may not be accompanied by

any increase in flue baffling.

Some manufacturers make water heaters with induced draft fans that, in addition to

pulling the combustion products through the water heater, also draw excess air into the flue gases

prior to venting. The additional air cools the flue gases lowering temperature enough so that

standard PVC piping can be used for venting. This eliminates any problems with corrosion.

Plastic piping is often cheaper and easier to install than sheet metal or masonry chimneys. While

this technique of flue gas dilution does not necessarily increase water heater efficiency by itself,

when combined with an improved flue baffle that increases RE, it can help avoid venting

problems.

As discussed earlier under venting issues, design options with REs greater than 80% were

not considered in this analysis. At REs beyond 80%, flue-loss efficiencies exceed 84% resulting

in flue gas condensation within the water heater's flue, leading to corrosion and a shortened life.

To ensure that condensation would not occur within the flue system, only flue baffle

EE-RM-97-900 COMMENT 38TT
54

improvements with maximum REs of 78% were included in design options selected for further

analysis. By keeping recovery efficiencies this low, it was assumed that forced- or induced-draft

blowers would not be needed to overcome increased pressure drops due to the improved baffle

system.

Table 32 summarizes the changes made to the analytic baseline model to simulate the

performance of a gas-fired water heater with an improved flue baffle. In order to model a water

heater with a 78% RE, the excess combustion air was decreased and the flue baffle heat

exchanger multiplier was increased.

Table 32. Gas-Fired Water Heater Modeling Differences Analytic Baseline Model vs. Model

with Improved Flue Baffle

Descriptive parameter Analytic Baseline w/ Improved Flue Baffle (RE = 78%)

Excess Combustion Air (%) 42.0 34.0

Flue baffle effectiveness multiplier 2.000 2.200

Electronic Ignition. The most commonly used ignition system in gas-fired storage water

heaters is a standing pilot ignition system. The disadvantage of a standing pilot is it bums gas

continuously at a rate of approximately 400 Btu/h (117 W), and only part of this heat is converted

to useful energy. In addition to the standing pilot, three electronic ignition devices are commonly

used in gas-fired appliancies:

* an intermittent pilot ignition device that by generating a spark lights a pilot, which in

turn lights the main burner

* an intermittent direct ignition device that lights the main burner directly by generating

a spark, and

* a hot surface ignition (HSI) device that lights the main burner directly by generating a

hot surface.

Unlike standing pilots that consume gas continuously, these devices operate only at the

beginning of each on-cycle. Although there is no increase in the steady-state efficiency with use

of electronic ignition devices, the overall fuel consumption may be reduced. Burner on-time may

increase to make up for the heat the standing pilot would have supplied during standby periods.

Electronic ignition devices require an outside electricity source for ignition, usually a 24

V or a 120 V system. The power draw of the electrically operated gas valve is between 5 W and

12 W, and power is consumed only when there is a call for heat. Electronic ignition systems also

require a control module, which houses the electronic control circuitry and consumes 6 W of

power during a call for heat. These systems also need an electronic thermostat that draws 1.2 W

of power during the heating period and 0.4 W of power during the standby period. The HSI is a

resistive device that draws about 2.5 amps at 120 V (about 300 W of power) for approximately

EE-RM-97-900 COMMENT 38TT
55

30 seconds during ignition.

For this analysis, an intermittent pilot ignition system was the only type of non-standing

pilot ignition system analyzed for gas-fired storage water heaters. The total on-cycle power

consumption was assumed to be 15.7 W while the total off-cycle power consumption was

assumed to be 0.4 W. Table 33 summarizes the changes made to the analytic baseline model to

simulate the performance of an intermittent pilot ignition system.

Table 33. Gas-Fired Water Heater Modeling Differences Analytic Baseline Model vs. Model

with Electronic Ignition

Descriptive parameter Analytic Baseline with Electronic Ignition

Pilot Input 400 Btu/hr (117 W) 0 Btu/hr (0 W)

On-cycle power consumption 0.0 W 15.7 W

Off-cycle power consumption 0.0 W 0.4 W

Flue Damper (Electromechanical). Gas-fired storage water heaters are equipped with a

draft hood connecting the flue to a vent pipe or chimney. During off-cycle, the water heater loses

heat by natural convection up the flue. A damper can be installed either at the flue exit or in the

vent pipe to minimize the off-cycle heat losses. A flue damper is installed upstream of the draft

diverter, while the vent damper is installed downstream of the draft diverter.

Electric flue dampers are activated by an external source of electricity. The dampers open

before combustion starts and close immediately after combustion stops. When the damper

reaches the open position, an interlock switch energizes the solenoid and enables the gas ignition

circuit. Therefore, the burner cannot be ignited when the damper is in the closed position.

Because the dampers open and close immediately, no bypass is needed. For flue dampers

installed on water heaters using a standing pilot, a knockout in the flue damper is provided to

vent the pilot's flue gases. Of course in this situation, off-cycle losses would be greater than

those in water heating equipment using a non-standing pilot ignition system. The electric flue

damper needs a 24-volt electric source and consumes about 5 W when the gas supply is off.

Flue dampers are assumed to have no effect on the RE of the water heater.

For this analysis, electromechanical flue dampers were analyzed only in conjunction with

electronic ignition systems. Since electricity is required for the operation of the flue damper, it

was assumed that the standing pilot would be converted over to an electronic ignition system in

order to take advantage of the electrical power that exists at the water heater. Flue dampers were

modeled according to the procedure outlined in the user's manual for TANK39. Typically,

TANK calculates the off-cycle pressure loss coefficient based on the physical characteristics of

the water heater. In the case of a flue damper, the off-cycle pressure loss coefficient is manually

1 determined based on the following expression:

e (c.f) 2

EE-RM-97-900 COMMENT 38TT
56

where;

ed = the effective pressure loss coefficient of the flue damper,

c = discharge coefficient of the flue damper, and

f = fraction of center flue area remaining open after the flue damper has closed

expressed by the following equation:

Dfwhere;

Df = the internal flue diameter, and

Dd = the electromechanical flue damper diameter.

Because flue dampers are usually not designed to completely seal the flue, the fraction of the

center flue remaining open after the damper closes is approximately 10%. Discharge coefficients

vary from a value of 0.6 for knife-edged damper plates to 1.0 for smooth-edged damper plates.

For purposes of this analysis, a value of 0.8 was assumed for the discharge coefficient while a

value of 10% was assumed for the fraction of the center flue remaining open in order to calculate

the pressure loss coefficient for a water heater utilizing a flue damper. Table 34 summarizes the

changes made to the analytic baseline model to simulate the performance of an electromechanical

flue damper.

Table 34. Gas-Fired Water Heater Modeling Differences: Analytic Baseline Model vs. Model

with Electromechanical Flue Damper

Descriptive parameter Analytic Baseline with Electromechanical Flue Damper

Off-cycle pressure loss coefficient 12.4047 156

Off-cycle power consumption 0.0 W 5.0 W

Side-Arm Heater. The side-arm heater design avoids large flue losses by removing the

flue from the center of the tank. Water is withdrawn from the bottom of the tank and heated over

a burner in a small, separate heat exchanger. Water is returned to the top of the tank. A small

circulation pump moves water through the heat exchanger when the burner is on. The burner

could have electronic ignition, which would reduce the pilot light losses. Auxiliary power is

supplied by a low-voltage plug-in transformer. A water heater using this design in combination

with electronic ignition and a plastic tank was commercially available until 1998.

The expected EF and RE for a gas-fired water heater with a side-arm heater were based

EE-RM-97-900 COMMENT 38TT
57

on information provided by Mr. Minniear 40 . Table 35 provides EF estimates for two types of 40

gallon (150 liter) gas-fired storage water heater with side-arm heaters and metal storage tanks.

One design is based on a 76% RE while the other is based on a 78% RE. Both designs

incorporate an intermittent pilot ignition device, 1.981 in. (5.032 cm) of HFC-245fa foam

insulation, and plastic heat traps.

Table 35. Side-Arm 40 gallon (150 liter) Gas-Fired Water Heater: Energy Factor Estimates

Water Heater Design Energy Factor

76% RE Side Ann Heater with intermittent pilot ignition device, 1.981 in. 0.655

(5.032 cm) foam insulation, and plastic heat traps

78% RE Side Arm Heater with intermittent pilot ignition device, 1.981 in. 0.668

(5.032 cm) foam insulation, and plastic heat traps

Because TANK cannot simulate the performance of water heaters equipped with side-arm

heaters, the WHAM energy calculation method was used to estimate its energy performance. If

both the EF and RE are known, WHAM can be used to determine the UA of the water heater

and, in turn, its energy consumption. Appendix B provides a detailed explanation of how the

WHAM energy calculation method was used to determine the energy consumption of side-arm

heater designs.

Since side-arm heaters require a small circulation pump to move water through the heat

exchanger, a component of the total energy input is due to the consumption of electrical energy.

For this analysis, it was assumed that the circulation pump had an on-cycle power consumption

of 30 W. The daily electrical energy use was determined by modeling the flue damper water

heater with the TANK simulation model and specifying an on- and off-cycle power consumption

equal to that assumed for a side-arm heater. Since side-arm heaters already need electricity to

operate, an intermittent pilot ignition system was also included as part of the side-arm heater.

For modeling purposes, the on-cycle power consumption was assumed to be 45.7 W (30 W for

the circulation pump and 15.7 W for the intermittent ignition device) while the off-cycle power

consumption was assumed to be 0.4 W (for the intermittent ignition device). Using TANK, this

results in a daily electrical energy consumption of 80.3 watt-hours.

Plastic Tank. The lower heat conductivity of a plastic tank reduces the amount of heat

conducted through the tank wall to the insulation. Plastic tanks cannot be used with standard

center-flue gas-fired water heaters because the plastic cannot withstand the high temperatures

produced by the flames. This option was considered only with indirect water heating techniques

(e.g., the side-arm water heater) that avoid flame temperature problems.

Because indirect water heating techniques cannot be modeled with TANK, the efficiency

benefits due to plastic tanks were not estimated with TANK. Plastic tanks were only analyzed in

the context of a side-arm heater design. Based on estimates provided by Mr. Minniear, a sidearm heater coupled with a plastic tank insulated with 2 nominal in. of foam insulation, (1.981 in.

EE-RM-97-900 COMMENT 38TT
58

(5.032 cm)) plastic tank, plastic heat traps, and an intermittent pilot ignition device yields only a

slightly higher EF than comparable metal tank designs. Table 36 provides the EF estimates for

two 40 gallon (150 liter) gas-fired side-arm storage water heater designs. One is based on a RE

of 76% while the other is based on a 78% RE. Both designs utilize a plastic tank, intermittent

pilot ignition device, 2 nominal in. (1.981 in. (5.032 cm) of HFC-245fa foam insulation, and

plastic heat traps.

Table 36. Side-Arm 40 gallon (150 liter) Gas-Fired Water Heater, Plastic Tank: Energy Factor

Estimates

Water Heater Design Energy Factor

76% RE Side Arm Heater with intermittent pilot ignition device, 1.981 in.

(5.032 cm) foam insulation, and plastic heat traps

78% RE Side Arm Heater with intermittent pilot ignition device, 1.981 in. 0675

(5.032 cm) foam insulation, and plastic heat traps

Design Option Manufacturer Costs

As with electric water heaters, manufacturer costs were primarily based upon data

provided by GAMA. The side-arm heater and plastic tank were the only design options, which

was analyzed using manufacturing cost provided by Mr. Minniear. All manufacturing cost

estimates were based upon the production of a 40 gallon (150 liter) gas-fired water heater and

were disaggregated into variable (material, labor, overhead, transportation) and fixed (capital,

product design) costs. Design option variable and fixed costs were provided as a per unit cost

and expressed as an incremental increase over the baseline design.

Existing Baseline Model. GAMA developed existing baseline model cost estimates for

a 40 gallon (150 liter) gas-fired storage water heater with 1 in. (2.5 cm) of foamed jacket

insulation blown with HCFC-141b. These baseline model costs were used for this Engineering

Analysis. Table 37 presents the baseline model manufacturer costs. The overhead includes the

transportation cost too. Note, no fixed costs were assumed for the baseline model.

Table 37. Gas-Fired Water Heater Existing Baseline Model: Manufacturer Costs

Variable Costs (per unit) Fixed Costs (per unit) Total

Product Mfg

Design Material Labor Overhead Total Capital Design Total Cost

Existing Baseline $75.02 $12.49 $50.10 $137.61 $0.00 $0.00 $0.00 $137.61

Analytical Baseline Model. In order to convert the baseline manufacturer costs

associated with foam insulation blown with HCFC-141b to that blown with HFC-245fa, the

amount and cost of materials associated with varying thicknesses of HCFC- 141 b and HFC-245fa

EE-RM-97-900 COMMENT 38TT
59

foam insulation were developed. Thus, the material costs associated with a particular level of

HFC-245fa insulation could easily be determined by adding to the baseline costs associated with

a comparable level ofHCFC-141b foam insulation. Tables 38 and 39 summarize the material

costs associated with varying levels of HCFC-141b and HFC-245fa foam insulation,

respectively. The material costs of HCFC-141b ($1/lb or $2.2/kg) as well as sheet metal cost

($0.30/lb or $0.66/kg), were based on estimates by Mr. Minniear 41 . The material costs of HFC245fa foam insulation ($1.32/lb or $2.9/kg) were based on estimates by Allied Signal, see Table

15.

Table 38. Gas-Fired Water Heater Material Costs Associated with varying thicknesses of HCFC141b Foam Insulation

Polyurethane Foam 141b Jacket Sheet Metal Misc Total

thickness volume' weight 2 cost 3 area thickness weight 4 cost' cost' cost

in. (cm) ft3 (m3

) lb (k) fi 2 (m2) ft3 (m3

) lb (kg)

0.98(2.49) 1.57(0.04) 3.15(1.43) $3.15 23.76(2.21) 0.038(0.001) 18.40(8.35) $5.52 $0.00 $8.66

1.48(3.76) 2.47(0.07) 4.93 (2.24) $4.93 25.43 (2.36) 0.040(0.001) 19.69(8.93) $5.91 $1.62 $12.46

1.98(5.03) 3.42(0.10) 6.83(3.10) $6.83 27.12(2.52) 0.043(0.001) 21.00(9.53) $6.30 $4.04 $17.17

2.48 (6.30) 4.43 (0.13) 8.86 (4.02) $8.86 28.85 (2.68) 0.046 (0.001) 22.34 (10.13) $6.70 $5.86 $21.43

2.98(7.57) 5.51(0.16) 11.02(5.00) $11.02 30.62(2.84) 0.048(0.001) 23.71 (10.75) $7.11 $8.59 $26.72

'40 gallon (150 liter) tank dimensions: dia. = 15.8 in (40.1 cm), length = 47.5 in (120.7 cm), combustion chamber height = 6.5 in (16.5 cm)

2 Foam density = 2 Ib/ft' (32 kg/m')

3 Foam cost = $1/lb ($2.2/kg) 4 Sheet metal density = 489 Ib/ft' (7833 kg/m3

)

5

Sheet metal cost = $0.30/lb ($0.66/kg)

6 Miscellaneous cost includes additional cost for foam dams to contain foram insulation in a larger cavity.

EE-RM-97-900 COMMENT 38TT
60

Table 39. Gas-Fired Water Heater Material Costs Associated with varying thicknesses of HFC245fa Foam Insulation

Polyurethane Foam 245fa Jacket Sheet Metal Misc Total

thickness' volume 2 weight3 cost 4 area thickness' weight 5 cost6 cost 7 cost

in. (cm) ft3 (m3) lb (kg) ft (m2

) ft (m) lb (kg)

1.00 (2.54) 1.61 (0.05) 3.21 (1.46) $4.24 23.82 (2.21) 0.038 (0.001) 18.44 (8.36) $5.53 i $0.00 $9.77

1.48 (3.76) 2.47 (0.07) 4.93 (2.24) $6.51 25.43 (2.36) 0.040 (0.001) 19.69 (8.93) $5.91 $1.62 $14.03

1.98(5.03) 3.42(0.10) 6.83(3.10) $9.02 27.12(2.52) 0.043(0.001) 21.00(9.53) $6.30 $4.04 $19.36

2.48(6.30) 4.43(0.13) 8.86(4.02) $11.70 128.85(2.68) 0.046(0.001) 22.34(10.13) $6.70 I $5.86 $24.26

2.98(7.57) 5.51(0.16) 11.02(5.00) $14.55 30.62(2.84) 0.089(0.001) 23.71 (10.75) $7.11 $8.59 $30.25

' Thickness increased due to increased conductivity of 245fa relative to 141 b.

240 gallon (150 liter) tank dimensions: dia. = 15.8 in (40.1 cm), length = 47.5 in (120.7 cm), combustion chamber height= 6.5 in (16.5 cm)

3 Foam density = 2 Ib/ft (32 kg/m') 4Foam cost = $1.32/lb ($2.9/kg) 5

Sheet metal density = 489 Ib/ft (7833 kg/m')

6 Sheet metal cost = $0.30/lb ($0.66/kg)

7 Miscellaneous cost includes additional cost for foram dams to contain foam insulation in a larger cavity.

As noted in Table 39, the actual thickness level for 1 nominal in. of HFC-245fa foam

insulation was assumed to be slightly greater than the thickness for HCFC-141b foam insulation

due to HFC-245fa's higher conductivity.

Table 40 presents the manufacturer cost estimates for a 40 gallon (150 liter) gas-fired

water heater with 1 nominal in. of HCFC-141 b foam insulation and the costs associated with the

same baseline model with HFC-245fa foam insulation. The material costs for the HCFC-141b

baseline model were adjusted upward by the difference in material costs ($ 1.11) calculated for

the HCFC-141b and HFC-245fa models.

Table 40. Gas-Fired Water Heater Baseline Model with HCFC-141b and HFC-245fa:

Manufacturer Costs

Variable Costs (per unit) Fixed Costs (per unit) Total

Product Mfg

Design Material Labor Overhead Total Capital Design Total Cost

Baselinew/141b-0.981 in(2.492cm) $75.02 $12.49 $50.10 $137.61 $0.00 $0.00 $0.00 $137.61

Baseline w/ 245fa- 1.0 in (2.5 cm) $76.13 $12.49 $50.10 $138.72 $0.00 $0.00 $0.00 $138.72

Analytical Baseline Model with Flammable Vapor Ignition Resistant Design. In

order to prevent the ignition of flammable vapors, gas-fired water heater manufacturers will need

to redesign their product. Based on discussions with the Water Heater Industry Joint Research

and Development Consortium, DOE assumed a placeholder value of $35 was added to the total

manufacturing cost ($15 variable costs & $20 fixed cost) for product redesign42. The design

would not require electricity at the water heater or modifications to the vent system. In addition.

EE-RM-97-900 COMMENT 38TT
61

DOE assumed that water hater efficiency would not change. Table 39 presents the manufacturer

cost estimates for the baseline model with the flammable vapor ignition resistant design.

Table 41. Gas-Fired Water Heater Analytic Baseline Model with Resistant Flammable Vapor

Ignition Design: Manufacturer Costs

Variable Costs (per unit) Fixed Costs (per unit) Total

Product Mfg

Design !Material Labor Overhead Total Capital Design Total Cost

Baseline with 245fa and Flammable

Vapor Ignition Resistant Design $91.13 $12.49 $50.10 $153.72 $20.00 $.0 0.00 1203.72

Heat Traps. Manufacturer costs for metal and plastic heat traps were based upon data

provided by GAMA. GAMA's data did not provide a separate cost data for metal and plastic

heat traps. Data from the heat trap manufacturer Perfection, Inc. was used as a reference. It was

assumed that heat trap material cost is based on the following design configurations: Metal heat

trap material costs for both the supply and draw lines were based on a /4-in. (1.9 cm) by 3-in. (7.6

cm) pipe nipple assembly design. Plastic heat trap material costs for the supply line were based

on a plastic drop-intube design while those for the draw line were based on a plastic cartridge

heat trap design within a combined outlet and and anode rod assembly. Table 42 summarizes

the incremental manufacturer costs for incorporating metal and plastic heat traps into a gas-fired

water heater. The costs reflect the addition of heat traps to both the supply and draw lines.

Table 42. Heat Traps for Gas-Fired Water Heaters: Incremental Manufacturer Costs

Incremental Variable Costs (per unit) Incremental Fixed Costs (per unit) Total

|>i~~ !iT~ ~ Product Incremental

Design 'Material Labor Overhead Total I Capital Design Total Mfg Cost

Heat Traps (metal) $2.75 $0.16 $0.21 $3.12 I $0.07 $0.13 $0.20 $3.32

Heat Traps (plastic) i $2.75 $0.16 $0.21 $3.12 $0.07 $0.13 $0.20 $3.32

1) Perfection Inc.'s data was almost identical for both types ($3.00 for plastic and $2.95 for metal heat traps); 2) GAMA's heat trap variable

costs are different for electric water heaters and gas-fired water heaters.

Increased Jacket Insulation. Since the current insulation blowing agent, HCFC-141b

will be phased out by 2003, manufacturer cost estimates for increases in the jacket insulation

were adjusted to account for insulation blown with HFC-245fa. Foam cost data were based on

information provided by Allied Signal. As presented earlier, Table 39 depicted the material costs

for varying levels of HFC-245fa foam insulation. GAMA provided variable and fixed cost data

for jacket insulation increases from a baseline level of 1.0 in. (2.54 cm) to a thickness of 2.0 in.

(5.1 cm) only. In order to generate variable and fixed cost data for the next level of insulation,

from a baseline level of 1.0 in. (2.54 cm) to a thickness of 2.5 in. (6.4 cm), the data provided by

M. Minniear was used to calculate ratios of variable and fixed cost for 2" insulation to 2.5"

insulation. GAMA's cost for 2.0 in. (5.1 cm) of insulation was multiplied by those ratios to

approximate the variable and fixed costs for 2.5 in. (6.4 cm) of insulation. Table 43 summarizes

EE-RM-97-900 COMMENT 38TT
62

the incremental manufacturer costs for jacket insulation increases from a baseline level of 1.0 in.

(2.54 cm) to a thicknesses of 1.981 in. (5.032 cm) and 2.481 in. (6.302 cm) (as provided in Table

39). As stated earlier, insulation thicknesses were limited to 2/ 2 in. (6.4 cm) due to installation

and shipping concerns.

Table 43. Increased Jacket Insulation for Gas-Fired Water Heaters: Incremental Manufacturer

Costs

|Incr. Variable Cost (per unit) Incr. Fixed Costs (per unit) Total

Product Incremental

Design_ _____Material Labor Overhead Tot CapitTotal CapiTotal Mfg Cost

Incr. Insulation- 1.981 in (5.032 cm) $9.59 $0.60 $4.93 $15.12 $0.85 $0.59 $1.44 $16.56

Incr. Insulation- 2.481 in (6.302 cm) $14.49 $1.20 $9.86 $25.55 $1.28 $1.18 $2.46 $28.01

Improved Flue Baffle. Manufacturer costs for the improved flue baffle design were

based on data from GAMA. Table 44 summarizes the incremental manufacturing costs for an

improved flue baffle. The costs were based on a design that increased the RE to 78%. It is

interesting to note that largest component of the manufacturing cost increase is the product

design.

Table 44. Improved Flue Baffle for Gas-Fired Water Heaters: Incremental Manufacturer Costs

Incr. Variable Cost (per unit) l Incr. Fixed Costs (per unit) Total

Product Incremental

Design Material Labor Overhead Total Capital Design Total l Mfg Cost

Improved Flue Baffle l $0.97 $1.29 $1.32 $3.58 $1.17 $1.72 $2.89 $6.47

Electronic Ignition. Manufacturer costs for electronic ignition were based on the

replacement of a standing pilot with an intermittent pilot ignition device. The cost of the

electronic ignition system was based on data from GAMA. Table 45 summarizes the incremental

manufacturing costs for switching from a standing pilot to an intermittent pilot ignition device.

Table 45. Electronic Ignition for Gas-Fired Water Heaters: Incremental Manufacturer Costs

Incr. Variable Cost (per unit) ! Incr. Fixed Costs (per unit) Total

Product Incremental

Design Material Labor Overhead Total Capital Design Total Mfg Cost

Electronic Ignition $43.78 $3.28 $11.72 $58.78 $2.09 $1.47 $3.56 $62.34

Flue Damper (Electromechanical). Manufacturer costs for including an

electromechanical flue damper with a gas-fired water heater were based on data from GAMA.

Table 46 summarizes the incremental manufacturing costs of putting a flue damper on a gas-fired

EE-RM-97-900 COMMENT 38TT
63

water heater. Because electromechanical flue dampers were analyzed only in conjunction with

electronic ignition systems, the incremental manufacturer costs associated with both design

options are also summarized in Table 46. As stated previously, because electricity is required for

the operation of the flue damper, it was assumed that the standing pilot would be converted to an

electronic ignition system in order to take advantage of the electrical power at the water heater.

Table 46. Flue Damper w/ Electronic Ignition for Gas-Fired Water Heaters: Incremental

Manufacturer Costs

Incr. Variable Cost (per unit) iIncr. Fixed Costs (per unit) Total

Product Incremental

Design Material Labor Overhead Total Capital Design Total Mfg Cost

Flue Damper $85.05 $4.12 $15.87 $105.04 $3.45 $2.03 $5.48 i $110.52

FlueDamper+Electr. Ignition $128.83 $7.40 $27.59 $163.82 $5.54 $3.50 $9.04 $172.86

Side-Arm Heater and Plastic Tank. Manufacturer costs for the side-arm heater for a

gas-fired water heater design were based on data from Mr. Minniear. Table 47 summarizes the

costs for four types of side-arm heater designs; 76% and 78 % RE designs that use a metal tank

and electronic ignition and 76% and 78% RE designs with a plastic tank and electronic ignition.

For this analysis it was assumed that the cost difference between the 76% and 78% RE designs

was equal to the cost of the improved flue baffle design. This assumption means that heat

exchanger costs for a 78% RE design would be higher than those for a 76% RE design. Because

side-arm heaters were analyzed only in conjunction with electronic ignition systems, the

incremental manufacturer costs associated with both design options are also summarized in Table

47. As discussed previously, plastic tanks cannot be considered as a stand-alone design option

for standard center-flue gas-fired water heaters due to the high temperature of combustion. Thus,

plastic tanks can only be considered with indirect heating designs, such as a side-arm heater.

Table 47. Side-Arm Heaters for Gas-Fired Water Heaters: Incremental Manufacturer Costs

> Incr. Variable Cost (per unit) Incr. Fixed Costs (per unit) Total

I A Product Incremental

Design Material Labor Overhead Total Capital Design Total MfgCost

76% RE Side-Arm Heater w/Metal Tank: $24.50 $2.10 $7.20 $33.80 $4.00 $10.00 $14.00 $47.80

78%RE Side-Arm Heaterw/MetalTank $25.47 $3.39 $8.52 $37.38 $5.17 $12.72 $16.89 $54.27

76% RE Side-Arm Heater w/ Plastic Tank. $29.75 $2.90 $9.25 $41.90 $8.00 $16.00 $24.00 $65.90

78% RE Side-Arm Heater w/ Plastic Tank: $30.72 $4.19 $10.57 $45.48 $9.17 $17.72 $26.89 $72.37

76% RE Side-Arm Heater w/Metal Tank $6. 76%RESide-Arn Heaterw/Me 6828 $5.38 $26.02 $99.68 $6.34 $3.49 $9.83 $109.51 including IID

78% RE Side-Arm Heater w/ Metal Tank

including IID $69.25 $6.67 $27.34 $103.26 $7.51 $5.21 $12.72 $115.98

76% RE Side-Arm Heater w/ Plastic Tank

including lID $73.53 $6.18 $30.22 $109.93 $9.34 $4.09 $13.43 $123.36

78% RE Side-Arm Heater w/ Plastic Tank

including lID $74.50 $7.47 $31.54 $113.51 $10.51 $5.81 $16.32 $129.83

EE-RM-97-900 COMMENT 38TT
64

Design Option Retail Prices

The retail price is considered to be the cost to the consumer of only the water heating

equipment. The retail price for an existing baseline 40 gallon (150 liter) gas-fired storage water

heater (with HCFC-141b foam insulation) was determined by contacting various plumbing

contractors and large retail chains. Since the price of a water heater depends on the length of the

manufacturer's warranty, only water heaters warrantied for 5 years were considered to be

baseline models. As with electric water heaters, the 5 year warranty was accepted as the shortest

warranty period offered by water heater manufacturers (although 1 year warranties have been

offered in special cases) and is typically reserved for those models which are produced in large

quantities (i.e., baseline models). A longer warranty period, in addition to raising the price, may

also indicate the presence of some design feature which would not normally be found in baseline

models. Table 48 provides the list of retail prices which went into developing the retail price of

the baseline model. For each price listed, the source for that price is also provided. All

information presented in Table 48 are from the LBNL Water Heater Database 43

As shown in Table 48, the average retail price for a baseline 40 gallon (150 liter) gasfired storage water heater is $149.94 (without taxes). As presented earlier, the baseline

manufacturer cost of a HCFC-141b-based water heater is $137.61. Using the average national

value for taxes of 5.20% (developed by A.D.L, 1998), yields a retail price of $157.74. Dividing

the retail price ($157.74) by the manufacturer cost ($137.61.) yields a manufacturer cost-to-retail

price markup of 1.15 (an exact value of 1.14626 is used as a multiplier).

The baseline manufacturer cost-to-retail price markup was assumed constant for the

design options considered for this analysis. Thus, the retail price for any modified design was

simply determined by multiplying its manufacturer cost by the derived markup of 1.15.

EE-RM-97-900 COMMENT 38TT
65

Table 48. 40-Gallon (150 liter) Gas-Fired Storage Water Heater Retail Prices

Source Manufacturer Brand Model Retail

Little Rock, AR American Water Heaters Amerimore G51-40T34-3NV $115.00

Little Rock, AR American Water Heaters Amerimore G51-40S33-3NV $116.00

Salt Lake City, UT American Water Heaters American Water Heaters G51-40T34-3NV $118.00

West Allis, WI American Water Heaters American Water Heaters Add in later $126.00

Chicago, IL American Water Heaters More-Flo G51-40T34-3NV $126.00

Minneapolis, MN American Water Heaters More-Flo G51-40T34-3NV $126.00

Nashville, TN American Water Heaters American Water Heaters DVG52-40S38-NV $127.00

Portland, OR State Industries Reliance 5-40-NORT $128.00

Reno, NV American Water Heaters American Water Heaters G51-40T34-3NV $128.00

Stockbridge, GA American Water Heaters Envirotemp G51-40T34-3NV $129.00

Atlanta, GA American Water Heaters PROLine G51-40S33-3NV $129.00

Atlanta, GA American Water Heaters PROLine G51-40S33-3NV $129.00

Marieeta, GA American Water Heaters Envirotemp G51-40T34-3NV $129.00

Las Vegas, NV State Industries Reliance 5-40-NORT $129.00

Sacramento, CA American Water Heaters American Water Heaters G5140T34-3NV $129.00

Atlanta, GA American Water Heaters PROLine G5140S33-3NV $129.00

Atlanta, GA American Water Heaters PROLine G51-40T34-3NV $129.00

Chicago, IL American Water Heaters More-Flo PVG52-40T50-3NV $130.00

Denver, CO State Industries Reliance 5-40-NORT $131.00

Phoenix, AZ State Industries Reliance 5-40-NORT $131.00

St. Louis, MO American Water Heaters American Water Heaters G5140T34-3NV $131.00

Oklahoma City, OK State Industries Reliance 5-40-NORT $131.00

New Orleans, LA American Water Heaters American Water Heaters G5140T34-3NV $131.00

Dallas, TX State Industries Reliance 5-40-NORT $132.00

Emeryville, CA American Water Heaters American Water Heaters G5140T34-3NV $133.00

Falls Church, VA American Water Heaters PROLine G5140T34-3NV $134.00

Orange, CA State Industries Reliance 5-40-NORT $134.00

West Allis, WI American Water Heaters Craftsman $134.00

Seattle, WA State Industries Reliance 5-40-NORT $134.00

Nashville, TN American Water Heaters American Water Heaters G51-40T34-3NV $135.00

Lexington, KY American Water Heaters American Water Heaters G51-40T34-3NV $135.00

Livermore, CA Sears/State Industries Kenmore $139.99

Bensalem, PA American Water Heaters Moreflow G51-40t34-NV $144.00

Charlotte, NC American Water Heaters $147.00

Charlotte, NC American Water Heaters More-Flo G5140T34-3NV $147.00

Richmond, CA Sears/State Industries Kenmore 33246 $160.00

Emeryville, CA American Water Heaters American Water Heaters G51-40S33-3NV $161.00

Parkersburg, WV A.O. Smith FSG40 $162.88

Livermore, CA Sears/State Industries Kenmore $164.99

Berkeley, CA Rheem Rheem 21V40-7N $167.00

Indianapolis, IN State Industries PRV40 $170.00

Berkeley, CA Rheem Rheem 21V40S-2 $177.00

Berkeley, CA Rheem Rheem 21VR40-7 $177.00

Bethpage, NY Rheem RH21V40 $178.50

Winchester, VA Rheem Rheem 21 V407 $184.00

Marion, IN A.O. Smith FSG40 $187.38

EE-RM-97-900 COMMENT 38TT
66

Source Manufacturer Brand Model Retail

Boston, MA State Industires POWERMISER 5 33246 $190.00

Boston, MA State Industires POWERMISER 5 33246 $200.00

Orange, CA State Industries Reliance 5-40-NBRT $209.00

Berkeley, CA Rheem Rheem 21V40T $222.00

Boston, MA State Industires ANNIV. SERIES 10 $250.00

Boston, MA State Industires POWERMISER 5 33246 $260.00

Average Retail Cost $149.94

Installation and Maintenance Costs

The installation cost is the cost to the consumer of installing the water heater and is not

considered part of the retail price. The cost of installation covers all labor and material costs

associated with the replacement of an existing water heater. Delivery, removal, and permit fees

are also included.

For the baseline water heater models, data was collected from the same sources as those

used to gather retail prices, to establish the installation cost of a 40 gallon (150 liter) baseline

gas-fired storage water heater. Table 49 lists the installation costs. The average installation cost

was determined to be $159.52. All information presented in Table 49 are from the LBNL Water

Heater Database44.

Table 49. 40-Gallon (150 liter) Gas-Fired Storage Water Heater Installation Costs

Source Manufacturer Brand Model Installation

Berkeley, CA Rheem Rheem 21V40-7N $65.00

Berkeley, CA Rheem Rheem 21V40S-2 $65.00

Berkeley, CA Rheem Rheem 21VR40-7 $65.00

Berkeley, CA Rheem Rheem 21V40T $65.00

Falls Church, VA American Water Heaters PROLine G51-40T34-3NV $75.00

Anchorage, AK Bradford White $90.00

Anchorage, AK Bradford White $90.00

Stockbridge, GA American Water Heaters Envirotemp G51-40T34-3NV $119.00

Salt Lake City, UT American Water Heaters American Water Heaters G51-40T34-3NV $125.00

Denver, CO State Industries Reliance 540-NORT $130.00

Little Rock, AR American Water Heaters Amerimore G51-40S33-3NV $130.00

Little Rock, AR American Water Heaters Amerimore G51-40T34-3NV $130.00

Little Rock, AR American Water Heaters Amerimore DVG52-40S38-NV $130.00

Phoenix, AZ State Industries Reliance 5-40-NORT $136.00

Atlanta, GA American Water Heaters PROLine G51-40S33-3NV $142.00

Atlanta, GA American Water Heaters PROLine G51-40S33-3NV $142.00

Nashville, TN American Water Heaters American Water Heaters G51-40T34-3NV $145.00

Nashville, TN American Water Heaters American Water Heaters DVG52-40S38-NV $145.00

Marieeta, GA American Water Heaters Envirotemp G51-40T34-3NV $149.00

Livermore, CA Sears/State Industries Kenmore $153.99

Livermore, CA Sears/State Industries Kenmore $153.99

EE-RM-97-900 COMMENT 38TT
67

Source Manufacturer Brand Model Installation

Reno, NV American Water Heaters American Water Heaters G51-40T34-3NV $154.00

Dallas, TX State Industries Reliance 5-40-NORT $155.00

Charlotte, NC American Water Heaters $155.00

Orange, CA State Industries Reliance 5-40-NORT $159.00

Orange, CA State Industries Reliance 5-40-NBRT $159.00

West Allis, WI American Standard American Standard $159.00

St. Louis, MO American Water Heaters American Water Heaters G51-40T34-3NV $160.00

Dale City, VA American Water Heaters Craftsman $169.00

Las Vegas, NV State Industries Reliance 5-40-NORT $170.00

Richmond, CA Sears/State Industries Kenmore 33246 $174.00

Charlotte, NC American Water Heaters More-Flo G51-40T34-3NV $175.00

Emeryville, CA American Water Heaters American Water Heaters G51-40T34-3NV $176.00

Emeryville, CA American Water Heaters American Water Heaters G51-40S33-3NV $176.00

Oklahoma City, OK State Industries Reliance 5-40-NORT $180.00

Lexington, KY American Water Heaters American Water Heaters G51-40T34-3NV $200.00

Chicago, IL American Water Heaters More-Flo PVG52-40T50-3NV $209.00

Chicago, IL American Water Heaters More-Flo G51-40T34-3NV $209.00

Sacramento, CA American Water Heaters American Water Heaters G51-40T34-3NV $210.00

Boston, MA State Industires ANNIV. SERIES 10 $220.00

Boston, MA State Industires POWERMISER 5 33246 $220.00

Boston, MA State Industires POWERMISER 5 33246 $220.00

Boston, MA State Industires POWERMISER 5 33246 $220.00

Bew Orleans, LA American Water Heaters American Water Heaters G51-40T34-3NV $225.00

Seattle, WA State Industries Reliance 5-40-NORT $231.00

Atlanta, GA American Water Heaters PROLine G51-40S33-3NV $234.00

Atlanta, GA American Water Heaters PROLine G51-40T34-3NV $234.00

Minneapolis, MN American Water Heaters More-Flo G51-40T34-3NV $258.00

Average Installation Cost $159.52

Four design options were assumed to increase the cost of installing a gas-fired water

heater: the improved flue baffle, electronic ignition, the electromechanical flue damper, and the

side-arm heater.

For several designs, TANK reported flue efficiency close to 80%. For those designs it

was assumed a Type B vent connector is required to ensure that condensation would not occur

within the vent system. The additional installation cost associated with this vent connector was

based on an analysis by GRI and independently verified by PNNL (see Appendix C). As

established by GRI, the cost for replacing a single-wall vent connector with a Type B double-wall

vent connector is $85 in 1990 dollars45 or $105.29 in 1998 dollarsa (conversions from 1990

dollars to 1998 dollars were adjusted by the consumer price index (CPI) from the Bureau of

a Values in 1990 dollars are converted to 1998 dollars by multiplying the 1990 value by

the ratio of the 1998 and 1990 CPI. The 1990 CPI for all urban consumers is 130.7. The 1998

CPI is based on the average CPI during the first three months of the year (161.9).

EE-RM-97-900 COMMENT 38TT
68

Labor Statistics4 6). It was determined that 51.3% of householdsa required a Type B vent

connector4 7. Thus, the average additional installation cost was determined by multiplying the

$105.29 cost by 51.3%. This yields a value of $54.01 in 1998 dollars as the representative

average installation cost for the improved flue baffle design, or other design options within

RE=78%.

The three remaining design options (electronic ignition, electromechanical flue damper,

and side-arm heater) all require electricity to operate. The installation cost was increased in order

to include the cost to bring electricity to the gas-fired water heater for these design options. This

installation cost estimate was also based on data from GRI48. Of the added installation cost,

$6.20 in 1990 dollars, or $7.68 in 1998 dollars, is required for labor and wiring of every water

heater with any of these three design options. Thirty-two percent of households will also require

an electrical outlet at the water heater. GRI estimated this cost at $66.15 in 1990 dollars 4 9; this is

equivalent to $81.94 in 1998 dollars. Thus, the average cost for installing an outlet was

determined by multiplying the $81.94 cost by 32%. This yields an average cost of $26.22 in

1998 dollars for the installation of an outlet. This value plus the wiring and labor cost of $7.68

yields a total representative added installation cost of $33.90 in 1998 dollars for the three design

options which require electricity to operate.

The electromechanical flue damper was the only design option that was assumed to

increase a gas-fired water heater's maintenance cost. The maintenance cost of the flue damper

was based on a prior DOE analysis50 , in which the national average flue damper maintenance cost

was estimated as $63.64 in 1990 dollars or $78.84 in 1998 dollars. For this analysis, the flue

damper was assumed to fail in the tenth year of operation. Using a 6% discount rate, this yields a

present value of $44.02 in 1998 dollars or an annualized maintenance cost over the ten year

period of $5.98.

With the exception of the electromechanical flue damper, information gathered to date

suggests that there is virtually no maintenance of residential gas-fired water heaters. Side-arm

heater designs may incur increased maintenance costs due to fouling of the heat exchanger from

hard water, but data has not been identified or provided to confirm this. It should be noted that

manufacturers recommend that water heaters be drained and flushed annually to minimize

deposition of sediment, maintain operating efficiency and prolong equipment life.

Cost-Efficiency Data

a The 51.3% value was determined by multiplying the total number of water heater

installations with either Type B vertical vents (42%) or masonry chimneys (48%) by the fraction

of households requiring a Type B vent connector (75%) and the fraction of households not

already utilizing Type B vent connectors (76%). Thus, the total number of household requiring a

Type B vent connector is represented by the following equation: (42% + 48%) · 75% 76% =

51.3%.

EE-RM-97-900 COMMENT 38TT
69

The results of the design option analysis for 40 gallon (150 liter) gas-fired storage water

heaters are presented in Tables 50 and 51. Included in the cost and efficiency tables are

disaggregated manufacturer costs, retail prices, installation costs, maintenance costs, energyefficiency and energy use data, and payback periods. Design options were added to the baseline

model in order of shortest payback period. The payback period for each set of design options

was calculated relative to the baseline design according to the following relationship:

ACC ARC+AIC

PA YBA CK - AA OC AEC+ AMC

where;

PAYBACK = payback period (years),

ACC = change in consumer cost relative to baseline, ($),

AOC = change in operating cost relative to baseline, ($/year),

ARC = change in retail cost relative to baseline, ($),

AIC = change in installation cost relative to baseline, ($),

AEC = change in energy cost relative to baseline, and ($/year),

AMC = change in annualized maintenance cost relative to baseline,

($/year).

The existing baseline design with HCFC-141b foam insulation is presented in Table 50 to

show the manufacturer cost and retail price differences between the baseline designs with HCFC141b and HFC-245fa. Also presented in Table 50 are the costs for incorporating a design to

resist igniting flammable vapors. For purposes of this analysis, the cost effectiveness of all

design options were evaluated in reference to the analytic baseline design with HFC-245fa and

the flammable vapor ignition resistant design. Energy costs were from national average energy

prices for 2003 from the 1998 Annual Energy Outlook".

The costs for all the design option combinations are shown in Table 50 and the efficiency

data is shown in Table 51. A design option selection process is presented as a flowchart in

Figure 3. The first selected design option.combination is "Analytical Baseline" plus "Heat

Traps", which has the shortest payback period - 2.2 years. This combination is called selection 1.

Selection 2 and selection 3 are branches from selection 1 and include "2 in. Jacket Insulation"

and "2.5 in. Jacket Insulation" design options. Based on the next shortest payback period,

selection 4 is chosen. It includes the "Side Arm Heater" design option and is built on selection 3.

The last is selection 5 - "Efficient Flue Baffle", which is based on selection 2. Table 50a and 5 la

contain cost data and efficiency data for the selected design combinations respectively. These

selected design combinations are used in the Life Cycle Cost Analysis.

Metal heat traps are not included in the cost-efficiency table because plastic heat traps are

more cost effective. The highest EFs are obtained with the side-arm heater designs. No designs

pay back in less than 2 years. The gas-fired water heater with heat traps, 2/2 in. of insulation,

electronic ignition and a mechanical flue damper has a .638 EF, energy savings of 3.96 million

EE-RM-97-900 COMMENT 38TT
70

Btu of natural gas per year and a payback of 18.96 years. The side-arm gas-fired water heater

with efficient flue baffle, 2/2 in. of insulation and electronic ignition has a .675 EF, energy

savings of 6.45 million Btu of natural gas and a payback of 7.05 years.

Figure 4 graphically depicts the relationship between both increased consumer cost and

increased operating cost versus EF.

Gas Fired Water Heaters

Design Option Selection Process

Analytic Baseline Opt. Oa

Opt. 0 + Heat

Traps (Opt. 1)

Opt. 1 + 2" '

insulation (Opt. 2) pt 2 &

i nsulation \(Opt. 3a) Opt. 3d Heater * Inreaeed RE

Opt. ___________________N 2.5Ba Opt. 4b 

I Opt. 2 + Efficient | /< 9\ , o f | opt 4Baffle

Opt. 3a Side- Ar + 

Arm Heater w/

Standard RE (Opt. -_

in---' ' ^ '~~sula / ~~Opt. ^ 3ae n1d & Electromechanical Flue St -'''- 40 ^

v Damper

Opt. 2 + Effici 5 Opt. 4 Efficient Flue

Flue Baffle t(Opt. 3o

Figure 3. Gas Fired Water Heaters Design Option Selection Process

EE-RM-97-900 COMMENT 38TT
71

EE-RM-97-900 COMMENT 38TT
72

Table 50. Cost Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater

Incremental Variable Costs (per unit) '" Incr. Fixed Costs (per unit) *' Total

Design Total Product Total Mfg Retail Install. Maint.

No. Design Options Material Labor Overhead Variable Capital Design Fixed Cost Price"' Cost' Cost'

0 Existing Baseline $75.02 $12.49 $50.10 $137.61 $0.00 $0.00 $0.00 $137.61 S157.74 $159.52 $0.00

Oa Analytic Baseline + Resistant Flammable Vapor $16.11 $0.00 $0.00 $16.11 $20.00 $0.00 $20.00 $173.72 $199.13 $159.52 $0.00

I Oa + Heat Trap $2.75 $0.16 $0.21 $3.12 $0.07 $0.13 $0.20 $177.04 $202.93 $159.52 $0.00

2 I + 2" Jacket Insulation $9.59 $0.60 $4.93 $15.12 $0.85 $0.59 $1.44 $193.60 $221.92 $159.52 $0.00

3a +2.5" Jacket Insulation $14.49 $1.20 $9.86 $25.55 $1.28 $1.18 $2.46 $205.05 $235.04 $159.52 $0.00

3b 2 + Improved Flue Baffle $0.97 $1.29 $1.32 $3.58 $1.17 $1.72 $2.89 $200.07 $229.33 $213.54 $0.00

3c 2 + Electronic Ignition & Flue Damper3 $128.83 $7.40 $27.59 $163.82 $5.54 $3.50 $9.04 $366.46 $320.06 $193.42 $5.98

3d 2 + Side-Arm Heater w/ Increased RE6 $69.25 $6.67 $27.34 $103.26 $7.51 $5.21 $12.72 $309.58 $354.86 $193.42 $0.00

4a 3a + Side-Arm leater w/Standard RE 7 $68.28 $5.38 $26.02 $99.68 $6.34 $3.49 $9.83 $314.56 $360.57 $193.42 $0.00

4b 3a + Improved Flue BaffleR $0.97 $1.29 $1.32 $3.58 $1.17 $1.72 $2.89 $211.52 $242.46 $213.54 $0.00

4c 3a + Electronic Ignition & Flue Damper9 $128.83 $7.40 $27.59 $163.82 $5.54 $3.50 $9.04 $377.91 $433.18 $193.42 $5.98

5 4a + Improved Flue Baffle'" $0.97 $1.29 $1.32 $3.58 $1.17 $1.72 $2.89 $321.03 $367.98 $247.44 $0.00

All costs and prices in 1998$.

2 Incremental variable and fixed costs are per unit costs.

' For the Existing Baseline Model with HCFC-141b, the TOTAL variable costs are provided.

Retail Prices are calculated based on the manufacturer cost-to-retail price markup of 1.14626.

Design option 3c: The incremental cost covers Electronic Ignition & Flue Damper.

The total cost includes Heat Trap and 2" Jacket Insulation

Design option 3d: The incremental cost covers 78% RE Side-Arm heater w/ Metal tank and Electronic Ignition

The total cost includes Heat Trap and 2" Jacket Insulation

7 Design option 4a: The incremental cost covers 76% RE Side-Arm heater w/ Metal tank and Electronic Ignition

The total cost includes Heat Trap and 2.5" Jacket Insulation

Design option 4b: The incremental cost covers Improved Flue Baffle.

The total cost includes Heat Trap and 2.5" Jacket Insulation

Design option 4c: The incremental cost covers Electronic Ignition & Flue Damper.

The total cost includes Heat Trap and 2.5" Jacket Insulation

'" Design option 5: The incremental cost covers Improved Flue Baffle.

Ihe total cost includes Heat Trap, 2.5" Jacket Insulation, 78% RE Side-Arm heater w/ Metal tank and Electronic Ignition.

EE-RM-97-900 COMMENT 38TT
73

Table 50a. Cost Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater - Selected Design Option Combinations

Incremental Variable Costs (per unit) ''. Incr. Fixed Costs (per unit) '1 Total

Selection Design Total Product Total Mfg Retail Install. Maint.

No. No. Design Options Material Labor Overhead Variable Capital Design Fixed Cost Price" Cost' Cost'

0 0 Existing Baseline' $75.02 $12.49 $50.10 $137.61 $0.00 $0.00 $0.00 $137.61 $157.74 $159.52 $0.00

Oa Oa Analytic Baseline + Resistant Flam. $16.11 $0.00 $0.00 $16.11 $20.00 $0.00 $20.00 $173.72 $199.13 $159.52 $0.00

I I Oa+ Heat Trap $2.75 $0.16 $0.21 $3.12 $0.07 $0.13 $0.20 $177.04 $202.93 $159.52 $0.00

2 2 1 +2" Jacket Insulation $9.59 $0.60 $4.93 $15.12 $0.85 $0.59 $1.44 $193.60 $221.92 $159.52 $0.00

3 3a 1 + 2.5" Jacket Insulation $14.49 $1.20 $9.86 $25.55 $1.28 $1.18 $2.46 $205.05 $235.04 $159.52 $0.00

4 4a 3a + Side-Arm Heater' $68.28 $5.38 $26.02 $99.68 $6.34 $3.49 $9.83 $314.55 $360.57 $193.42 $0.00

5 3b 2 + Improved Flue Baffle $0.97 $1.29 $1.32 $3.58 $1.17 $1.72 $2.89 $200.07 $229.33 $213.54 $0.00

All costs and prices in 1998$.

2 Incremental variable and fixed costs are per unit costs.

'For the Existing Baseline Model with HCFC-141b, the TOTAL variable costs are provided.

4 Retail Prices are calculated based on the Manufacturer to Retail Markup of 1.0896.

'Side-arm heater with metal tank includes electronic ignition, 2.5"insulation, heat traps.

EE-RM-97-900 COMMENT 38TT
74

Table 51. Efficiency Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater

Fuel Energy Use Electrical Energy Use Payback

Design Energy Recovery UA Thermal Daily Yearly Daily Yearly Period2

No. Design Options Factor Efficiency Efficiency Btuday MMBu/ear kWh/day kWh/year years

0 Existing Baseline 0.545 75.48% 13.82 77.90% 78289 28.58 0.00 0.00 NA

Oa Analytic Baseline + Resistant Flammable Vapor 0.544 75.56% 13.86 77.90% 78298 28.58 0.00 0.00 NA

I Oa + Heat Trap 0.554 75.57% 12.96 77.90% 77523 28.30 0.00 0.00 2.31

2 I + 2" Jacket Insulation 0.580 76.21% 11.04 77.85% 75159 27.43 0.00 0.00 3.42

3a I + 2.5" Jacket Insulation 0.587 76.38% 10.64 77.74% 74647 27.25 0.00 0.00 4.63

3b 2 + Improved Flue Baffle 0.595 78.01% 10.69 79.75% 72784 26.57 0.00 0.00 7.19

3c 2 + Electronic Ignition & Flue Damper 0.638 76.52% 5.95 77.85% 67465 24.62 0.14 52.77 19.81

3d 2 + Side-Arm Heater w/ Improved Flue Baffle 0.655 76.00% 5.68 - 62483 22.81 0.08 29.32 5.82

4a 3a + Side-Arm Heater 0.662 76.00% 5.24 - 61819 22.56 0.08 29.32 5.97

4b 3a + Improved Flue Baffle 0.600 78.03% 10.37 79.57% 72530 26.47 0.00 0.00 7.19

4c 3a + Electronic Ignition & Flue Damper 0.645 76.71% 5.52 77.84% 66792 24.38 0145 52.77 18.75

5 4a + Improved Flue Baffle 0.675 78.00% 5.36 - 60618 22.13 0.08 29.32 7.28

'Annual operating cost for Payback Period calculation established with a gas price of $5.82 /MMBtu and an electricity price of $0.0787 /kWh in 1998$.

Thermal Efficiency is used to determine the risk of venting system corrosion...

EE-RM-97-900 COMMENT 38TT
75

Table 51a. Efficiency Table for 40 gallon (150 liter) Gas-Fired Storage Water Heater - Selected Design Option Combinations

Fuel Energy Use Electrical Energy Use Payback

Selection Design Energy Recovery UA Thermal Daily Yearly Daily Yearly Period'

No. No. Design Options Factor Efficiency Efficiency 2 Btu/day MMBtu/year kWh/day kWh/year years

0 0 Existing Baseline 0.545 75.48% 13.82 77.90% 78289 28.58 0.00 0.00 NA

Oa Oa Analytic Baseline + Resistant Flam. 0.544 75.56% 13.86 77.90% 78298 28.58 0.00 0.00 NA

I I Oa + Heat Trap (plastic) 0.554 75.57% 12.96 77.90% 77523 28.30 0.00 0.00 2.31

2 2 1 + 2" Jacket Insulation 0.580 76.21% 11.04 77.85% 75159 27.43 0.00 0.00 3.42

3 3a I + 2.5" Jacket Insulation 0.587 76.38% 10.64 77.74% 74647 27.25 0.00 0.00 4.63

4 4a 3a + Side-Arm Heater 0.662 76.00% 5.23 - 61819 22.56 0.08 29.32 5.97

5 3b 2 + Improved Flue Baffle 0.595 78.01% 10.69 - 72784 26.57 0.08 0.00 7.19

Annual operating cost for Payback Period calculation established with a gas price of $5.82 /MMBtu and an electricity price of $0.0787 /kWh in 1998$.

2 Thermal Efficiency is used to determine the risk of venting system corrosion.

EE-RM-97-900 COMMENT 38TT
76

540 4 180

i -- Consumer Cost I

X 500 - 1------- - Operating Cost __ 170

a 460 - _ - - - . _____ 160

S I s ;J I a

340 2 130

0.52 0.54 0.56 0.58 0.60 0.62 0.64 0.66 0.68

Energy Factor

Figure 4. 40 gallon (150 liter) Gas-Fired Storage Water Heaters: Total Consumer Cost and

Oil-fired water heaters are typically constructed using a glass-lined metal storage tank

located above an insulated combustion chamber. There are two basic design types, center flue

and rear flue (also referred to as floating tank design). Both designs utilize an oil-burner

consisting of oil pump, blower, ignition device, and controls. The two basic designs are

differentiated by flue location. In a center flue design, the combustion products are vented

through a center flue that goes up the middle of the storage tank. By contrast, rear-flue designs

provide for the combustion gases to travel around the outside of the storage tank. The rear-flue

design provides significantly more heat exchange area between the storage tank and flue gases.

Thus, these designs typically have higher RE and input ratings compared to center flue designs of

similar storage volumes. However, because the hot exhaust gases travel near the outside of the

water heater, there is also more heat transfer area for off-cycle losses to the flue. Because centerflue designs are much more common in residential use, the DOE analysis for oil-fired water

heaters heaters only only considers considers center-flue designs. center-flue designs.

EE-RM-97-900 COMMENT 38TT
77

The pump and blower of the water heater are powered by a single motor. The blower

provides for proper mixing of oil and combustion air. The oil and air mixture is electrically

ignited with a high voltage spark. In most burners, this spark operates continuously as long as

the burner is firing. Since the spark does not operate when the burner is off, this is referred to as

an intermittent ignition system.

Oil-fired water heaters have higher input ratings than similar sized gas-fired storage water

heaters, resulting in higher recovery rates. Because of the relatively high recovery rates, the

industry uses storage tank volumes slightly smaller than those used with gas-fired or electric

storage water heaters. The oil-fired water heater industry uses two common tank volumes, each

with a corresponding input rating. These are either 32 gallon (120 liter) water heaters with an

input rating between 85,000 to 95,000 Btu/hr (24,905 to 27,835 watts) or, 50 gallon (189 liter)

water heaters with an input rating between 100,000 to 110,000 Btu/hr (29,300 to 32,230 watts).

Discussions with installers and manufacturers indicate that the 32 gallon water heater size

represents the bulk of the residential market and this is the size used as a baseline model in the

engineering analysis.

Existing Baseline Model

The first step in the design options analysis is to characterize the energy usage of the

existing model. As stated previously, the existing oil-fired water heater used in this analysis has

an EF of 0.529, an RE of 75% and an energy consumption of 90,962 Btu/hr (90,000 Btu/hr of

fuel oil and 282 W [962 Btu/hr] for the pump and blower motor) during firing.

Table 52 summarizes the primary baseline characteristics. The jacket insulation was

assumed to be 1 in. of HCFC-141b foam, characteristic of water heater models known to closely

match DOE's baseline performance criteria. Many existing oil-fired water heater models use

fiberglass insulation, however these models typically use more than 1 in. of insulation and have

better performance. Note that the analysis did not address the modeling of the combustion

chamber and hence no detailed description of the combustion chamber was needed. The values

in Table 50 describe the water heater in engineering terms for use in the heat transfer

calculations.

Table 52. Oil-Fired Water Heater Baseline Model Characteristics

Descriptive parameter Value

Input Rating (oil) 90000 Btu/hr (26377 W)

On-cycle power consumption 282 W

Off-cycle power consumption 0.0 W

Tank Dimensions

Inside Diameter 17.892 in. (40.366 cm)

Steel Wall Thickness 0.054 in. (0.1372 cm)

Height 32.7 in. (83.1 cm)

Volume 32.0 gallons (120 liter)

EE-RM-97-900 COMMENT 38TT
78

Jacket Description

Foam insulation thickness 0.981 in. (2.492 cm)

Sheet metal thickness 0.019 in. (0.0483 cm)

Thermal conductivity of foamed 0.0140 Btu/hr-ft °F (0.0242

Outer Jacket Emissivity 0.87

Flue Description

Internal Diameter 6.00 in. (15.24 cm)

In order to determine the daily energy consumption, the first step is to determine the

hours of operation. This is done with the following equation.

Qdr,, BOH= draw (A) EF. Po

where;

BOH = burner operating hours, the number of hours per day the burner is on

(hrs/day),

Qdraw = the amount of heat added to the water in the daily draw under the DOE

test procedure, (41,094 Btu/day [43,346 kJ/day]),

Pon = the total energy consumption rate (both electrical and fuel oil) when

the burner is firing (Btu/hr)

For the existing model, this results in 0.854 burner operating hours per day. Using the

DOE test procedure as a guideline, the daily energy consumption is calculated from the electrical

and oil input rates multiplied by the number of operating.hours per day. This results in an oil

consumption of 76,860 Btu/day (81,072 kJ/day) and an electrical energy consumption of 241

Wh/day.

The UA from the DOE test procedure was estimated using the following equation:

1 1

EF P,,

((ta --t-n b 24 RE 1 (

Qdra.w i R Pon

Plugging in the appropriate existing model values of EF, RE, and Pon results in a UA of

14.494 Btu/hr-°F (7.64 W/°C) for the existing model. By definition, this UA consists of standby

heat losses through the tank shell, through fittings, and from the flue during the off-cycle. Table

53 summarizes the results for the energy characteristics of the existing baseline model.

Table 53. Performance Characteristics for Existing Baseline Oil-Fired Water Heater

EE-RM-97-900 COMMENT 38TT
79

Description UA RE EF Oil Use Electrical Use

Btu/hr °F (W/°C) Btu/day (kJ/day) Wh/day

Existing Baseline 14.494 (7.64) 75% 0.529 76,860 (81,072) 241

The continuous losses, on-cycle flue losses, and off-cycle flue losses are determined from

two equations. The first equation sets two definitions of total daily heat loss equal. It states that

the sum of the rates of loss multiplied by the hours of each type of loss equals the total

consumption minus delivered energy. The second equation is based on the definition of RE, i.e.,

the total on-cycle losses equal the energy input minus the hot water energy removed from a tank

during the recovery portion of the DOE test procedure. The two equations can be written as

follows:

24-Losscontinuous + (24-BOH) Loss_Flue_off + BOH Lossflue_on = Qda /EF - Qd (C)

Losscontinuous + Lossjlue_on = Input (1 - RE) (D)

where;

Loss_continuous = continuous losses through the jacket insulation and out the

fittings, (Btu/hr) or (Watts),

Lossflue_on = on-cycle losses up the flue, (Btu/hr) or (Watts),

Lossflue_off = off-cycle losses up the flue as well as other off-cycle noncontinuous losses, (Btu/hr) or (Watts),

These losses are not used for calculating annual energy consumption, rather they are used

as the basis for differences in heat loss rates for other design options.

Analytic Model. Similarly to gas water heaters, the existing model's HCFC-141 b foam

insulation was replaced with HFC-245fa foam insulation due to the impending phase out of

HCFC-141b in 2003. HFC-245fa has a 3.0% higher conductivity than HCFC-141b and for this

design option, the conductivity value of the foam insulation in the existing model was increased

by 3.0% to a value of 0.0144 Btu/hr-ft-°F (0.0249 W/m *K). To maintain the same R-value of

the insulation (and thus maintain constant UA and RE values for the water heater) the thickness

of the nominal 1-in. of foam insulation surrounding the tank was increased from 0.981 in. (2.492

cm) actual thickness to 1.01 in. (2.57 cm). This increase in insulation thickness also resulted in

an increase of jacket material. Table 54 summarizes the changes that were made to the existing

model with HCFC-141b to provide the same performance with HFC-245fa (see Table 53). All

further design options assume the use of HFC-245fa for the tank insulation. Table 54

summarizes the results for the energy characteristics of the analytic baseline model.

EE-RM-97-900 COMMENT 38TT
80

Table 54. Oil-Fired Water Heater Modeling Differences: Existing Model with HCFC-141b vs.

Analytic Model with HFC

Descriptive Parameter Existing Model Analytic Model

Jacket Description

Foam insulation thickness 0.981 in. (2.492 cm) 1.01 in. (2.57 cm)

Thermal conductivity of 0.0140 Btu/hr-ft-F (0.0242 0.0144 Btu/hr-ft-°F (0.0249

foamed assembly W/m-K) W/m-K)

Table 55. Performance Characteristics for Analytic Oil-Fired Water Heater

Description UA RE EF Oil Use Electrical Use

Btu/hr °F (W/°C) Btu/day (kJ/day) Wh/day

Analytic Baseline 14.494 (7.64) 75% 0.529 76,860 (81,072) 241

Heat Traps. Two types of heat traps were analyzed for oil-fired water heaters: metal

and plastic. Both types of heat traps prevent the losses associated with the circulation of hot

water into the piping distribution system.

An estimate for the reduction of fitting heat losses due to heat traps added to the analytic

model was based on the analysis of the same design option applied to gas-fired water heaters.

Results from TANK simulations (see analysis of gas-fired water heaters) suggests that metal heat

traps reduce the UA of a water heater tank by 0.318 Btu/hr-°F (0.168 W/°C) during the DOE test.

The TANK analysis suggested plastic heat traps reduced the UA of the tank by 0.899 Btu/hr-°F

(0.474 W/°C). There is no impact on the RE of the analytic model. Subtracting these UA

reductions from the UA of the analytic oil-fired model and plugging the new UA into equation

(B) without changing the values for the other parameters from the analytic models yields a new

estimate for EF. The results of this analysis are shown in Table 56.

Table 56. Analysis Results for Design Option #1 (Heat Traps)

Design Option #1 UA RE EF Oil Use Electrical Use

Btu/hr °F (W/C) Btu/day (kJ/day) W-h/day

Metal Heat Trap 14.176 (7.476) 75% 0.532 76,363 (80,547) 239

Plastic Heat Trap 13.595 (7.17) 75% 0.539 75,456 (79,590) 236

For this analysis, plastic heat traps will be the chosen design option. Manufacturing costs

appear to be roughly comparable between metal and plastic traps and plastic heat traps are

considerably more effective in reducing the water heater standby losses.

Note, using the results from TANK in this manner is slightly conservative. Since oilfired water heaters have larger recovery rates, they spend more of the "Standby" portion of the

EE-RM-97-900 COMMENT 38TT
81

DOE test not firing. Thus, they will have longer periods for which heat traps are useful and

consequently heat traps should have slightly higher benefits on oil-fired water heaters compared

with gas-fired water heaters. This has not been accounted for in this analysis.

Increased Jacket Insulation. This design option replaces the nominal 1-in. (2.54 cm) of

foam insulation surrounding the storage tank in the existing tank design with 2 in. (5.08 cm) of

polyurethane foam insulation around the sides and top of the tank. The diameter of the tank

increases to 22 in. (56 cm) and the total height of the water heater (including the combustion

chamber) increases to 51 (130 cm) in.. It is assumed that there are no changes to the thickness of

insulation surrounding the combustion chamber and no benefit has been calculated for this. No

other changes to the tank design are assumed in this analysis except to enlarge the entire water

heater jacket to accommodate the increased thickness of insulation.

A water heater designer will either increase the fiberglass insulation thickness around the

combustion chamber, or increase the internal dimensions of the combustion chamber to maintain

a smooth cylindrical jacket on the water heater. These will add additional costs to the design.

The addition of insulation may require a way to recess the burner or to increase the length of the

burner blast tube to maintain proper placement of the nozzle in the combustion chamber. This

analysis does not account for any modifications to the heat loss from the combustion chamber.

Jacket heat losses are calculated as conductive losses through the insulation to the jacket

in series with convective and radiative heat transfer from the jacket to the surrounding air and

environment. The side insulation is modeled as a hollow cylinder with the inner diameter equal

to the tank diameter (18 in. [45.7 cm]) and the same height as the tank (32.7 in. [83.1 cm]). The

top insulation is modeled as a disk (18 in. diameter [45.7 cm]) with a hole for the flue in the

center (6 in. diameter [15.2 cm])). The details of the calculation of the total conductive heat loss

from the top and sides of the storage are provided in Appendix E.

Both RE and UA are changed by this reduction in total jacket heat loss as it occurs

continuously during water heater use. Since jacket losses are continuous losses, they are related

to the RE through equation (D):

Loss_continuous + Losslue_on = Po, (1 - RE) (D)

Thus,

RE = - (Losscontinuous + Loss_flue_on) / Po (E)

And subtracting the RE for two different levels of jacket loss when all other losses are held

constant gives

RE2 - RE, = (Loss_continuous, - Loss continuous) / Po, (F)

or

EE-RM-97-900 COMMENT 38TT
82

RE2 - RE, = (Jacket_loss, - Jacketloss) /Po, (G)

In the DOE test procedure, the UA represents the average rate of tank energy input

needed to maintain the tank at a constant temperature during standby. The standby heat loss rate

is calculated as:

Standby heat loss rate = UA (Tan - Tam (H)

This "standby heat loss rate" is the average rate of heat input needed to maintain a tank at

a constant temperature during standby. It includes continuous losses, flue losses when firing, and

flue losses and piping losses during the off-cycle. An overall energy balance on the standby

period yields:

UA-(Tta, - Tb)-(24 - BOH&a) = (Loss_continuous + LossJlue_off.(24 - BOH) +

BOH,-,Pan(1 - RE) (I)

where;

BOHda = Burner operating time to make up for hot water drawn from the tank

(hr),

BOHs, = Burner operating time to make up for standby losses (hr).

BOHs, can be calculated from the total energy required during the standby period divided

by the energy input during firing. The energy required to make up for losses during the standby

period is equal to the energy input for the whole DOE test minus the energy that is actually used

to heat water removed from the tank. In equation form, BOH,, is:

BOHs, = I/Po, Qdr, (I/EF-1/RE) (J)

And by default

BOHdrw = BOH-BOHs, (K)

Inserting equation (J) in equation (K) and solving for the loss components gives

UA (Tin-Tamb) (24 BOH+BOHs,,)- Q. (I- RE)- ( F- (L)

Losscontinuos + Lossflu rff = 2- 24 - BOH

Plugging in the known parameters for the analytic model water heater, and water heater

with plastic heat traps gives combined Loss_continuous + LossJlue_offvalues of 742 Btu/hr (217

W), and 695 Btu/hr (204 W) respectively.

With the addition of more insulation, the continuous losses from the plastic heat trap

design option are reduced by the difference in the jacket losses between the design with 2 in. (5.1

EE-RM-97-900 COMMENT 38TT
83

cm) of insulation (design option 2) and the same design with 1 in. (2.5 cm) of insulation (design

option 1 - heat traps). By solving the equations (A), (B), (J) and (L), the UA value and EF value

can be found that provides the new combined Loss_continuous +Loss_flue_off value for the water

heater with 2 in. (5.1 cm) insulation. Table 57 shows the results of this procedure.

Table 57. Analysis Results for Design Options 2 - 2" Jacket Insulation

Design Option Actual Calculated UA, RE EF Oil Use Electrical

Insulation Shell Loss, Btu/hr- Btu/day Use

Thickness "F (kJ/day)

in. (cm) Btu/hr (W) ( /°C) (W-h/day)

2" Jacket 1.981 89.2 12.241 75.1% 0.555 73,285 230

Insulation + (4.82) (26.1) (6.46) (77,301)

Heat Traps

Improved Flue Baffle. As described for gas-fired storage water heaters, improved flue baffle

designs allow the extraction of more heat from the exhaust gases and increase the flue-loss (and hence

recovery) efficiency of the water heater.

The oil-fired water heater analysis assumes that the improved flue baffle is added after heat traps and

2" jacket insulation. The energy savings for this design option are calculated by assuming that

modification of the flue baffle will provide more efficient heat transfer to the storage tank. This

design option will allow the water heater to achieve a RE of 0.78 by impacting reduction of

Flue_loss_on only. No modifications to Flue loss_offor Loss_continuous are assumed with this

design option.

There do not appear to be significant concerns with condensing flue products at a RE of 0.78.

The references regarding the existing rear-flue oil-fired water heaters report REs in this range.

Additionally, the premium water heater products sold by Bock Water Heaters all exceed this level of

RE 5 2, 5 3 .

Improving the RE alone, from 0.75 to 0.78, while maintaining the sum of Flue_loss_off and

Loss_continuous at 626 Btu/hr (183 W) as in the previous design option (2" jacket insulation)

provides an EF of 0.576 as shown in Table 58.

Table 58. Analysis Results for Design Option 3 - Improved Flue Baffle

Design Option UA RE EF Oil Use Electrical

Btu/hr- "F Btu/day Use

(W/°"C) (kJ/day) (W-h/day)

Improved Flue 11.786 (6.216) 78% 0.576 70,562 (74,429) 221

Baffle + 2" Jacket

EE-RM-97-900 COMMENT 38TT
84

Insulation + Heat

Traps

Increased Heat Exchanger Surface Area. This is a broad area of design options, generically

referred to as Increased Heat Exchange Surface Area. The suggested design option makes use of

small projections from the inner flue surface to: 1) increase the heat transfer area and 2) increase

turbulence along the inner flue wall. One manufacturer presently builds water heaters that use a flue

with many small rectangular fins attached in a helical pattern on the inside flue surface. Variations

of this model have the highest efficiency rating listed in the GAMA directory for oil-fired water

heaters.

This design option is used here to describe a number of possible design modifications that

would increase the surface area for heat exchange between the flue gases and water. These could

include increased flue diameter with improved baffling, multiple flues, or internally finned flues.

Presently, the only design feature on the U.S. market representative of this design option is the Bock

Turboflue system. The Turboflue design uses many small rectangular fins welded in a helical pattern

on the inside of the flue. The fins provide increased surface area for heat exchange with the flue gases

and they create turbulence in the flue. The use of this type of internally finned flue is assumed to

preclude the use of improved flue baffles, and hence the increased heat exchanger surface area design

option is really an alternative to the improved flue baffle design option.

The energy performance of the increased heat exchanger surface area design option is modeled

by increasing the RE of the 2" jacket insulation (design option 2) to 0.82. Several of the water heater

models that include the Turboflue in their design have a listed RE of 0.82. As was done when

considering the improved flue baffle design, no modifications to Flue_loss_ofor Losscontinuous

are assumed with this design option.

Improving the RE alone, from 0.75 to 0.82 while maintaining the sum of Flue_loss_off and

Loss_continuous at 626 Btu/hr (183 watts) (as in design option 2) provides an energy factor of 0.606.

Table 59 shows the resulting performance for Design Option 4 - Increased Heat Exchanger Area.

EE-RM-97-900 COMMENT 38TT
85

Table 59. Analysis Results for Design Option 4 - Increased Heat Exchanger Area

Design Option UA RE EF Oil Use Electrical

Btu/hr- °F Btu/day (kJ/day) Use

(W/°C) (W-h/day)

Increased Heat 11.216 (5.915) 82% 0.606 67,149 (70,829) 210

Exchanger Area

+

2" Jacket

Insulation + Heat

Traps

It should be noted that the energy factor estimate arrived at above may be conservative. An

examination of the energy performance parameters of several of the water heater models that use the

Turboflue design suggested much better energy performance can be achieved. For example, a 32

gallon (121 liter) water heater model 32PP (Bock) utilizes the internally finned Turboflue design and

has 1" jacket insulation. However, this model reports an energy factor of 0.66 and an RE of 0.82.

Bock's standard design model 32E, also incorporating the Turboflue design, has a reported energy

factor of 0.63 and an RE of 0.82.

To illustrate this example, the energy losses for the model 32PP design were partitioned as

was done for the analytic model, but using the EF, RE and rated input of the 32PP model. Inserting

an EF of 0.66, RE of 0.82, and rated input of 104,000 Btu/hr (30,472 W) from the GAMA directory

into equation (B) results in a UA value of 7.652 Btu/hr (4.036 W/°C). Note however, that it should

actually be easier to achieve the RE of 0.82 on a water heater when the rated input is the same as the

analytic model unit. If the partitioning of losses is done using the EF of 0.66, RE of 0.82, and rated

input of 90,962 Btu/hr (26,652 W), the resultant UA is 7.676 Btu/hr- F (4.052 W/°C). Both of these

examples suggest a considerable reduction in UA above what has been assumed for the increased

heat exchanger surface area design option. Standby losses for the Bock 32PP model are reduced

significantly from that estimated for the increased heat exchanger surface area design option. It is

not clear how much of this reduction in standby loss can be attributed to the Turboflue design

(possibly by restricting air movement during the off-cycle) and how much is achieved through other

means.

Interrupted Ignition. Interrupted ignition devices allow for the ignition spark to be turned

off after a flame has been established. Interrupted ignition devices will provide electrical energy

savings since the time the spark is operating is shorter than with the intermittent ignition systems in

use on present water heater designs. Intermittent ignition systems provide spark continually while

the burner is operating. Note, interrupted ignition systems may also increase the life of the spark

electrodes somewhat and may reduce maintenance costs.

EE-RM-97-900 COMMENT 38TT
86

Interrupted ignition provides electrical energy savings by shutting off the transformer used

to make the sparks. A typical intermittent ignition system utilizing an iron-core transformer may

draw approximately 1.7 Amps at 110 V during operation61. It does this for all burner operation hours,

so the daily electrical energy use for the ignition system for the increased heat exchanger surface area

design option (the most efficient case of the previous design options) would be calculated as:

Intermittentlgnition_Energy = (1. 7Amps) (110 0V)BOH (S)

For the design option 3 - increased heat exchanger surface area, BOH is 0.746 hrs/day from

equation (A).

Equation (S) ignores any power factor relationships in the transformer or electronic circuitry.

The Intermittent_Ignition_Energy for the increased heat exchanger surface area design option is then

calculated to be 140 wh/day.

For an interrupted ignition system, the system fires for approximately 20 seconds each time

the burner is ignited. The duration of each water-heater on-cycle is a function of the usage pattern,

but the DOE test procedure, with six 10.3-gallon draws per day, will serve as the basis for this

analysis. For most water heater designs, there will be a single recovery for each draw, with the

length of each recovery period given by 1/6' of BOHw (see equation Q). For the increased heat

exchanger surface area design option water heater, BOHdw equals 0.551 hrs and the recovery period

after each draw is thus 0.092 hrs.

Additionally, during the standby period there will be one or more occasions for the burner

to fire to make up for standby losses. The working assumption is that the average tank temperature

drops 20°F below the set point before firing is initiated, as dictated by the typical water-heater

thermostat deadband. The energy required for each recovery is then the product of the actual storage

volume of the water heater (estimated at 95% of the rated volume), the density and heat capacity of

the water, and the water temperature rise during firing. The time for each individual recovery during

standby can then be estimated as

BOHrecoverysandby = ( Vol, dens C,) (Trise) / (Po RE) (M)

where;

BOHrecoverystandby = the average time for each recovery during standby (hr)

Volnk = 0.95 * rated tank volume (gal)

Trse = the difference between the average tank temperature before and

after recovery (°F)

Solving the above equation yields an average BOHrecovey, stan equal to 0.0676 hr/day.

The number of draws during standby equals BOHst / BOH recoverystandby Using design option

3 - increased heat exchanger surface area as a base, this is equal to 2.125 draws during the standby

period. Thus, on average, the DOE test procedure would require the burner to fire an average of

4' -

EE-RM-97-900 COMMENT 38TT
87

8.125 times per day. At 20 seconds of igniter operation per firing, this requires 0.045 hours of

ignition operation per day.

The difference between intermittent ignition and interrupted ignition operating time is thus

0.701 hrs per day (0.746 hr - 0.045 hr), saving 131 wh/day of electrical energy. This represents 447

Btu/day reduction in the Loss_burner_on losses. If this energy savings is averaged over the total

burner operating hours of 0.749 hrs/day for the increased heat exchanger surface area design option,

this represents an average reduction in electrical power draw of 176 W (602 Btu/hr).

Since the Pon is reduced by 602 Btu/hr (176 W) and the output of the water heater is

unaffected, the definition of RE can be used to construct an equation for the new RE when the design

goes to interrupted ignition.

RE_interrupted = (RE_intermittent Polintermittent) / (Pointerrupted) (N)

For the water heater described by the increased heat exchanger surface area design option,

the change from an intermittant to an interrupted ignition results in an increase in RE from 0.820 to

0.825.

The UA is also affected, since there is some burner operation during the standby period.

Again, since the energy input to the tank during the standby period (represented by UA) is changed

while the heat energy to the water during standby does not change, the ratio of the UA of the

intermittent ignition system to the UA of the interrupted ignition system is equal to the ratio of the

input (Pon) for the intermittent system to the input of the interrupted ignition system. Hence,

UAinterrupted = UA_intermittent .(Pointerrupted / Pointermittent) (0)

And solving, UA_interrupted = 11.142 Btu/hr-°F (5.88 W/°C). This UA, in combination

with a calculated RE of 0.825 results in a EF of 0.610 from equation (B).

The same interrupted ignition analysis can be performed on the improved flue baffle design

option. The resulting performance parameters are an RE of 0.785, UA of 11.708 Btu/hr- F (6.17

W/°C), and EF of 0.580. Table 60 shows the resulting performance for Design Option 5 -

Interrupted Ignition.

EE-RM-97-900 COMMENT 38TT
88

Table 60. Analysis Results for Design Option 5 - Interrupted Ignition

Design Description UA RE EF Oil Use Electrical

Option Btu/hr- °F Btu/day Use

(W/ "C) (kJ/day) (W-h/day)

5a Interrupted 11.708 (6.175) 78.5% 0.580 70,562 83

Ignition + (70,829)

Improved

Flue Baffle

5b Interrupted 11.142 (5.876) 82.5% 0.610 67,151 79

Ignition + (70,829)

Increased

Heat

Exchanger

Area

NOTE: The savings indicated from the interrupted ignition design option are based on the

use of a conventional magnetic transformer to provide high voltages in the ignition system.

Electronic high voltage generators used in electronic igniter circuitry typically use about 0.5 Amps,

or less than a third the current draw of magnetic igniter circuitry6',62. Assuming the same hours of

burner operation as from design option 3 - increased heat exchange, the transition to electronic

ignition circuitry from magnetic ignition circuitry in an intermittent ignition system would save 90

Wh/day. This is 70% of the energy saved from going to an interrupted ignition system. However,

the adoption of an interrupted ignition system in a water heater with electronic igniter circuitry

would result in net energy savings of only 51 Wh/day (176 Btu/day) as compared with intermittent

electronic-ignition circuitry. Discussions with oil-fired water heater manufacturers indicates that

electronic ignition circuitry is not commonly used in residential water heater burners, but is an

available technology.

Design Option Manufacturer Costs

Manufacturing cost estimates for the oil-fired water heater design options are broken down

into variable and fixed costs for each design option. These cost estimates are shown in Table 59

and the assumptions and sources behind the estimates are discussed below. Note that all fixed

conversion costs have been amortized over a five year period unless otherwise noted, and also

amortized over an assumed shipment volume of 5,000 units annually.

Existing Baseline. Baseline cost for the oil-fired water heat tank (without burner) was

estimated based on data provided by Mr. Minniear under contract to LBNL63. It was recognized

that manufacturers of oil-fired water heaters use both fiberglass and foam in their baseline

models. For the purposes of this analysis however, the cost for the baseline model, whether

foam or fiberglass insulated, are assumed to be equivalent. A calculation of the volume of foam

and shell material for the baseline model was made independently of the data supplied by Mr.

EE-RM-97-900 COMMENT 38TT
89

Minniear. For a 32 gal baseline model the total mass of the insulation was estimated at 2.77 lbs

of HCFC141b foam. The unit price for the HCFC141 b based insulation was estimated at

$1.00/lb, yielding a total cost of the insulation for the 32 gallon water heater of $2.77/unit.

Total shell material is 16.87 lbs of steel at $0.30/lb resulting in a manufacturer cost of $5.06.

Total material cost for insulation and shell is $7.83. This cost information was used in

determining the cost impact of increasing the insulation thickness on oil fired water heaters.

Analytic design option. The analytic model assumed 1.01 in. of HFC245fa based

insulation on top and sides of tank. For 32 gal tank, total mass of the insulation was estimated

at 2.86 lbs. At $1.32/lb estimated cost for HFC245fa based insulation, total insulation cost was

estimated at $3.77. Total shell material was estimated to be 16.93 lbs of steel at $0.30/lb for a

total shell cost $5.08. Total material cost for foam and shell is $8.85, an addition of $1.02 for

materials over the baseline model. Since the phase out ofHCFC141b as a foaming agent is

unrelated to the DOE's energy efficiency mandate and will be borne by the manufacturers

regardless of mandated efficiency improvements, fixed costs for the analytic design option have

not been estimated.

Heat Traps. Variable cost estimates for heat traps are based on data gathered by Mr.

Minniear. Variable costs for heat traps were also estimated by a second consultant, Mr. Eugene

West. Both estimates were very comparable. Mr. Minniear's estimates are used here as they

provided the higher cost (more conservative) estimate and were broken out into variable

material, labor, and overhead costs. Fixed conversion costs to incorporate heat traps were

developed from product design cost estimates provided by Mr. West 4 65. For a small

manufacturer, capital cost impact to incorporate heat traps was deemed negligible.

2" Jacket Insulation. Variable costs to increase insulation from 1 to 2 nominal in. of (1.01

to 1.981 in. actual thickness) of HFC-245fa based insulation were estimated based on a nominal

1 in. increase in foam on both the top and side walls of the tank. Total foam mass for 2 in. of

insulation was estimated at 6.01 Ibs. At $1.32/lb for an HFC-245fa based foam, the total foam

cost is estimated at $7.93. The corresponding increase in tank jacket size increased the total

mass of jacket steel to 19.16 Ibs. Assuming an estimated $0.30/lb for jacket metal provided a

jacket cost estimated at $5.75. Total material cost for foam and shell is $13.68. An additional

cost of $0.76 for miscellaneous costs such as foam stop blocks and larger shipping cartons was

incorporated into the material costs based on data provided by Mr. West65. Additional labor cost

of $0.29/unit and additional overhead burdens of 0.99/unit, provided by the same source, were

also incorporated into the variable cost. Finally, the addition of insulation can affect the

shipping cost for the water heaters. No data for the increased shipping cost for an oil-fired water

heater was provided to LBNL or PNNL; however, an estimate for this impact on shipping cost

was made based on GAMA's estimated increase in shipping costs of $2.56 for an increase of 1

EE-RM-97-900 COMMENT 38TT
90

in of insulation on gas-fired water heaters66. This value was added to the variable cost overhead,

resulting in a net cost increase to $9.43 in variable cost over that calculated for the analytic

model.

Fixed conversion costs for this design option were based on data provided by Mr. West67,

who estimated that a small manufacturer, using spin forming to shape the top and bottom pans

for the water heater, would incur an estimated $18,000 in engineering costs for this design

option, and a further $20,000 in capital expenses to modify the production line65. It is noted

here that a manufacturer who used a die stamping method to produce the top and bottom pans

could expect approximately $100,000 in new die costs alone. However, it was believed that for

a large manufacturer, cost for dies to cut and form the top and bottom pans would likely have

most of that cost amortized over an existing, similar diameter, gas product line.

In addition to the above costs, discussions with manufacturers and installers of oil-fired

water heaters have indicated that at least one-half of all installations of oil-fired water heaters

are retrofits of a new water heater to an existing oil burner. The oil burner life is typically at

least twice that of the typical water heater tank, however in some cases if a new model or brand

of water-heater is installed it may be impossible or costly to fit to an existing burner and a

complete installation of tank and new burner will be undertaken.

Since the cost of a new burner is a significant fraction of the cost of the water heater tank

on most models, it is desirable to be able to attach an existing burner onto a new water heater.

This is a significant problem since the extra insulation thickness would affect the burner

placement and hence the combustion characteristics of the water heater. The solution, suggested

by several industry members; was for the manufacturer to provide a kit that allowed replacement

of the nozzle and blast tube on the existing burner with a nozzle and blast tube that was suitable

for a new, heavily insulated, model. The estimated cost for manufacturing and stocking this kit

was between $20 and $40 based on input from Mr. West68. The midpoint of that range, plus a

labor charge of $6.50 (20 minutes of service at $19.50/hour) is used as an additional cost when

tanks utilizing this design option are retrofit to existing burners.

Improved Flue Baffles. Variable costs for improved flue baffles were estimated as

$3.75 for material, $0.55 for labor, and $1.00 per unit for overhead costs based on estimates

provided by Max Minniear. Fixed costs for improving the flue baffle design are estimated at

$300,000 for production improvements and $500,000 for product design cost based on estimates

provided by Mr. Minniear.

Increased Heat Exchanger Surface. Variable costs for providing increased heat

exchanger surface area were estimated at $17.25/unit for material costs, $1.75/unit for labor

costs and $4.25/unit in overhead. Fixed conversion costs for this design option were estimated

at $1,500,000 for production improvements and $500,000 for product design costs. The fixed

cost estimates are based on Bock's Turboflue model.

EE-RM-97-900 COMMENT 38TT
91

Interrupted Ignition. Variable costs to incorporate interrupted ignition circuitry in oil

burners was estimated at $16.50 material costs based on data provided by Mr. Minniear.

Discussions with a burner manufacturer 69 indicated that the burner manufacturers cost

differential for interrupted versus intermittent controls was presently between $10 and $15 and

that typically these controls are installed on the burner by the burner manufacturer. The burner

units with controls are then sent to the water heater manufacturer who subsequently ships the

burner to the distributer or equipment dealer. There were not anticipated to be any additional

overhead or labor costs for interrupted ignition controls over intermittent ignition controls. It

was also the opinion of the person consulted that in the near future, interrupted controls would

likely be the primary control option offered on all burners. However, no attempt was made to

indicate the effect of this on the interrupted ignition control cost.

No fixed capital costs are anticipated for interrupted ignition. Design costs for the water

heater manufacturer are predominantly related to testing and certification of the water heater.

These costs are estimated at $25,000 based on similar product testing costs for increased

insulation and heat traps submitted by Mr. West. It is assumed that these costs are amortized

over a 5 year period.

DOE hopes that GAMA will gather cost data for these design options from GAMA

members who produce oil-fired water heaters. If GAMA supply manufacturer cost data, DOE

will revise the analysis with the GAMA data and use the consultants data as an independent

check on the GAMA data. As of this writing, GAMA has been unsuccessful in gathering this

cost data for oil-fired water heaters.

The cost for all the considered design option combinations are shown in Table 61 and

the cost for the selected design options is presented in Table 61a. The first selected design

option combination is "Analytical Baseline" plus "Heat Traps", which has the shortest payback

period - 3.8 years. This combination is called design option 1. Selection 2 "2 in. of Jacket

Insulation" is based on design option 1. Based on the next shortest payback period, design

option 3 is chosen. It includes "Improved Flue Baffle" design option and is built on selection 2.

The last is selection 5 - "Interrupted Ignition", which is also based on design option 3. Table 62

and Table 62a presents accordingly the relative first cost, performance and annual energy use

predicted for the considered design options and for the selected design options used in this

analysis. Those selected design combinations are further used in the Life Cycle Cost Analysis.

EE-RM-97-900 COMMENT 38TT
92

Table 61. Cost Table for 32 gallon Oil-Fired Storage Water Heater Design Options

Incremental Variable Costs (per unit) '12 Incr. Fixed Costs (per unit) '12 Total Mfg to

Design Total Product Total Mfg Retail Retail Install. Maint.

No. Design Options Material Labor Overhead Variable Capital Design Fixed Cost Markup Price' Cost' Cost'

0 Baseline (HCFC14 b) - I" foam3 $85.00 $18.25 $36.00 $139.25 $0.00 $0.00 $0.00 $139.25 3.20 $445.60 $491.00 $97.14

Oa Analytic (HFC245fa)- I" foam $1.02 $0.00 $0.00 $0.00 $0.00 $0.00 $10.00 $140.27 3.20 $448.86 $491.00 $97.14

I Oa + Heat Trap (plastic) $2.95 $0.05 $0.15 $3.15 $0.00 $1.52 $1.52 $144.94 3.20 $463.81 $491.00 $97.14

2 I + Increased Insulation to 1.981" (5.032 cm)4 $5.59 $0.29 $3.55 $9.43 $0.80 $0.72 $1.52 $155.89 3.20 $498.85 $509.25' $97.14

3 2 + Improved Flue Baffle (78% RE)4 $3.75 $0.55 $1.00 $5.30 $12.00 $20.00 $32.00 $193.19 3.20 $618.21 $509.25' $97.14

4 2 + Increased Heat Exchanger Surface4 $17.25 $1.75 $4.25 $23.25 $60.00 $20.00 $80.00 $259.14 3.20 $829.25 $509.25' $97.14

5a 3 +Interrupted Ignition4 $16.50 $0.00 $0.00 $16.50 $0.00 $1.00 $1.00 $210.69 3.20 $674.21 $509.254 $97.14

5b 4 +interrupted Ignition4 $16.50 $0.00 $0.00 $16.50 $0.00 $1.0 .001.00 $ 276.64 3.20 $885.25 $509.25' $97.14

All costs and prices in 1998$.

2 Incremental variable and fixed costs are per unit costs.

For the Baseline Model with HCFC-141b, the TOTAL variable costs are provided.

' Includes additional installation cost for burner conversion kit for 50% of existing market

EE-RM-97-900 COMMENT 38TT
93

Consumer Cost, Installation, and Maintenance Costs for oil fired water heaters.

Sales and installation of residential oil-fired water heaters are typically done by a local

residential heating oil dealer. Hence, in most cases, the purchase and installation of the water

heater is as a package, making it somewhat difficult to break out installation cost from purchase

price. A phone survey of 29 companies dealing in oil-fired water heating equipment was made,

with 13 companies providing some form of consumer price data to PNNL. Based on that survey

as well as discussion with water heater and burner manufacturers and two oil-heating associations,

the following costs were established.

Typical consumer cost for a base performance oil-fired water heater without burner: $446

Typical consumer cost for an oil burner for an oil-fired water heater: $285

Typical installation cost for new oil-fired water heater $300-$700

The estimated installation cost for a typical oil-fired water heater was estimated at $491

based on data provided by seven dealers in the northeastern U.S.70. In addition, it was

established that at least 50% of oil-fired water heater installations involve fitting a new water

heater tank to an existing burner. For the purpose of this analysis, it is assumed that 50% of all

oil-fired water heaters sold are for retrofit to an existing burner. Therefore, 50% of the

installations of water heaters with 2" of insulation would require an oil burner modification kit.

On average, the installation cost would rise to $509.25.

A typical manufacturer to consumer markup of 320% was used across all design options

based on the $446 figure for the existing baseline oil-fired water heater cost (without burner), and

the estimated manufacturing cost of $139.25 is shown on Table 59.

A typical maintenance contract cost of $97.14/yr was included in Table 59. It is based on

data provided by a phone survey discussed previously. This charge is highly variable, depending

on the presence of other oil-fired equipment in the residence. Since none of the design options is

anticipated to impact maintenance significantly, this charge has no bearing on the final

engineering analysis of the design options. It may however impact the final economic analysis

when evaluating possible fuel switching.

Relative Cost vs. Efficiency for Oil-fired Water Heater Design Options

Table 62 presents the relative first cost, performance and annual energy use predicted for

the design options considered in this analysis. Table 62a presents the relative first cost,

performance and annual energy use predicted for the design options selected from this analysis. It

also shows the annual energy cost and estimated simple payback for each design option. Annual

energy costs were based on residential energy rates of $7.522/MMBtu of oil and $0.0787/kWh of

electricity. Design options were selected based on the payback and the energy factor. Those

design options well beyond the average life of an oil-fired water heater were not selected.

EE-RM-97-900 COMMENT 38TT
94

EE-RM-97-900 COMMENT 38TT
95

Table 62. Energy Impact and Simple Payback of Oil-Fired Water Heater Design Options

Recover Fuel Energy Use Electrical Energy Annual

Design Factory Retail Install. Energy Efficienc UA Daily Yearly Daily Yearly Energy Simple

No. Design Options Cost Price Cost Factor (%) Btu/hr- Btu/day MMBtu/ Wh/day kWh/yr Cost' Payback

0 Existing $139.25 $445.60 $491.00 0.529 0.750 14.494 76860 28.05 241 87.9 $217.94 --

Oa Analytic model w/HFC-245fa $140.27 $448.86 $491.00 0.529 0.750 14.494 76860 28.05 241 87.9 $217.94 ---

I Oa + Heat Traps $144.94 $463.81 $491.00 0.539 0.750 13.595 75456 27.54 236 86.3 $213.96 3.8

2 1 + 2 in. foam insulation $155.89 $498.85 $509.25 0.555 0.751 12.241 73285 26.75 230 83.8 $207.80 8.7

3 2 + Improved Flue Baffles $193.19 $618.21 $509.25 0.576 0.780 11.786 70562 25.76 221 80.7 $200.08 13.1

4 2 + Increased Heat Exchanger $259.14 $829.25 $509.25 0.606 0.820 11.216 67149 24.51 210 76.8 $190.40 17.9

5a 3 + Interrupted Ignition $210.69 $674.21 $509.25 0.580 0.785 11.708 70562 25.76 83 30.3 $196.11 14.1

5b 4 + Interrupted Ignition $276.64 $885.25 $509.25 0.610 0.825 11.142 67151 24.51 79 29.0 $186.64 14.1

'Annual energy costs are based on residential energy rates of $7.522/MMBtu of oil and $0.0787/kWh of electricity.

Table 62a. Energy Impact and Simple Payback of Selected Oil-Fired Water Heater Design Options

Recover Fuel Energy Use Electrical Energy Annual

Design Factory Retail Install. Energy Efficienc UA Daily Yearly Daily Yearly Energy Simple

No. Design Options Cost Price Cost Factor (%) Btu/hr- Btu/day MMBtu/ Wh/day kh/yr Cost' Payback

0 Existing $139.25 $445.60 $491.00 0.529 0.750 14.494 76860 28.05 241 87.9 $217.94 ---

Oa Analytic model w/HFC-245fa $140.27 $448.86 $491.00 0.529 0.750 14.494 76860 28.05 241 87.9 $217.94 ---

I Oa+ Heat Traps $144.94 $463.81 $491.00 0.539 0.750 13.595 75456 27.54 236 86.3 $213.96 3.8

2 1 + 2 in. foam insulation $155.89 $498.85 $509.25 0.555 0.751 12.241 73285 26.75 230 83.8 $207.80 8.7

3 2 + Improved Flue Baffles $193.19 $618.21 $509.25 0.576 0.780 11.786 70562 25.76 221 80.7 $200.08 13.1

5a 3 + Interrupted Ignition $210.69 $674.21 $509.25 0.580 0.785 11.708 70.562 25.76 83 30.3 $196.11 14.1

Annual energy costs are based on residential energy rates of $7.522/MMBtu of oil and $0.0787/kWh of electricity.

EE-RM-97-900 COMMENT 38TT
96

REFERENCES

1. Department of Energy, Energy Information Administration, Annual Energy Outlook 1998

(AE098), http://www.eia.doe.gov/oiaf/aeo98/earlyrel.html, December 18, 1997.

2. 10 Code of Federal Regulations, Part 430- Energy Conservation Programfor Consumer

Products Energy Conservation Program for Consumer Products, Appendix E to Subpart B

- Uniform Test Methodfor Measuring the Energy Consumption of Water Heaters.

3. Department of Energy, Energy Information Administration, Annual Energy Outlook 1998

(AE098), http://www.eia.doe.gov/oiaf/aeo98/earlyrel.html, December 18, 1997.

4. Gas Appliance Manufacturers Association, October 1997, Consumers' Directory of Certified

Efficiency Ratings for Residential Heating and Water Heating Equipment, Arlington, VA

5. U.S. Census Bureau; Current Industrial Reportfor Major Household Appliances (MA36F),

1995; published 18 September 1996; <ftp://ftp.census.gov/pub/industry/ma36f95.wkl>

6. Paul, D. D., Sheppard, W. J., Whitacre, G. R., Fischer, R. D., Rutz, A. L., Locklin, D. W.,

Crisafulli, J. J., Stickford, G. H., Murray, J. G., Landstrom, D. K., Talbert, S. G., Buhr, A.

R., DeWerth, D. W., Farnsworth, C. A., Loria, A. R., & Pietsch, J. A. (1991). Assessment of

Technologyfor Improving the Efficiency of Residential Gas Water Heaters, Topical Report

No. GRI-92/0298). Battelle.

7. Barbour, Edward C., Dieckman, John T., and Nowicki, Brian J., Market Disposition of

High-Efficiency Water Heating Equipment, Final Report, Arthur D. Little, Inc., reference no.

46230, Washington, DC, prepared for Office of Building Equipment, Office of Building

Technologies, State and Government Programs, U.S. Department of Energy, November

1996,

8. Water Heater Rulemaking Framework (June 11, 1997)

http://www.eren.doe.gov/buildings/codes_standards/posted/whbb8O8.pdf

9. National Appliance Energy Conservation Act (NAECA). 1987. Public Law 100-12.

10. Federal Technology Alert. Sep. 1995. "Residential Heat Pump Water Heaters", prepared

by Pacific Northwest National Laboratory for the Federal Energy Management Program,

U.S. Department of Energy, Washington, D.C.

11. Arthur D. Little, Inc., "Market Disposition of High-Efficiency Water Heating Equipment",

1996.

12. 10 Code of Federal Regulations, Part 430, op. cit.

13. Hiller, Carl C., Lowenstein, Andrew I., Merriam, Richard L.,.WATSIM User's Manual,

Version 1.0: EPRIDetailed Water Heating Simulation Model User 's Manual, Electric Power

Research Institute, Palo Alto, CA, TR-101702, October 1992,

EE-RM-97-900 COMMENT 38TT
97

14. Paul, D.D.; Whitacre, G.R.; Crisafulli, J.J.; Fischer, R.D.; Rutz, A.L.; Murray, J.G.;

Holderbaum, G.S., TANK Computer Program User's Manual with Diskettes: An Interactive

Personal Computer Program to Aid in the Design and Analysis of Storage-Type Water

Heaters. prepared for Gas Research Institute GRI-93/0186, Battelle Memorial Institute,

Columbus, OH, July 1993

15. DOE, GRI, LBNL and PNNL, conference call, July 23, 1998.

16. Lutz, J.D., C.D.Whitehead, A.Lekov, D.Winiarski, G.J.Rosenquist, WHAM: A Simplified

Energy Consumption Equation for Water Heaters, Proceedings of the ACEEE 1998

Summer Study on Energy Efficiency in Buildings, American Council for an Energy Efficient

Economy (ACEEE), Washington, DC, 1998

17. U.S. Office of the Federal Register. 1993. Code of Federal Regulations, Title 40,

Environment. Part 82: Protection of Stratospheric Ozone; Final Rule. Washington, DC.

Vol. 58, No. 236, December 10, 1993.

18. McGee, I.E., Dobransky, M. A., and Ingold, K.A., HFC-245fa as a BlowingAgentfor Water

Heater Foam Insulation, Bayer Corporation, Pittsburgh, PA pp 170-173 in Proceedings of

the Polyurethanes EXPO' 96, sponsored by the Polyurethane Division of The Society of the

Plastics Industry, Inc., Las Vegas, NV October 20-23, 1996.

19. Ghadiali N.D., presentation to GRI's Gas Water Heater Technical Advisory Group, Battelle,

Columbus, OH, p.5, December 1997

20. Topping, R.F., and Benedek, K.R., Flammable Vapor Test Methodology Development for

Gas-Fired Water Heaters, Arthur D. Little, Inc., Cambridge, MA, April 1996, prepared for

Gas Research Institute, GRI-96/0102.

21. Crisafulli, J J.; Pate, A. D.; Philips, D. B.; Talbert, S. G.; and Rutz, A. L. Gas Water Heater

Venting Issues andAlternatives., GRI-96/0443, Battelle Memorial Institute, Columbus, OH,

December 1996. prepared for Gas Research Institute.

22. Philips, D.B., Talbert, S.G., Whitacre, G.R., Crisafulli, J.J., and Rutz, A.L., Categorization

Criteria for Residential Draft-Hood-Equipped Gas Water Heaters, GRI-95/0198, Battelle,

Columbus, OH, October 1995, prepared for Gas Research Institute.

23. National Fuel Gas Code - An American National Standard, ANSI Z223.1 -1996, National Fire

Protection Association, Quincy, Massachusetts, 1996, pp.51-53

24. Carl Hiller, personal communication, conversation with Greg Rosenquist, November 1997

25. Gas Research Institute, TANK Computer Program User's Manual, report GRI-93/0186,

prepared by Battele, Columbus, OH, 1993

EE-RM-97-900 COMMENT 38TT
98

26. Nisson, J.D. Ned, ed. 1994. "Simple Heat Trap for Water Heaters," Energy Design Update,

Vol. 14, No. 10, New York, p 14.

27. Harvey, J.A. "Making Your Water Heater More Efficient." Home Mechanix, March, 1994,

p.1 4.

28. Hiller, 1992, p. C-7. Op. cit.

29. Rheem Manufacturing Company, Water Heater Division, "Marathon High Performance,

High Efficiency, Lifetime Gas Water Heater," Form No. 101-41, 10-93 BP, Montgomery,

AL, 1993

30. Max Minniear, personal communication, e-mail to Jim Lutz, LBNL, Feb. 25, 1998

31. Dave Williams, Allied Signal, personal communication, telephone conversation with Jim

Lutz, LBNL, March 17, 1998

32. lain Gilchrist, Perfection, Inc., Madison, OH, personal communication, fax to Judy

Roberson, LBNL, March, 13, 1998

33. LBNL Water Heater Database, under continuous development, 1998.

34. Ibid.

35. Department of Energy, Annual Energy Outlook 1998 (AE098), 1997, Op. cit.

36. Ghadiali N.D., 1997, p.2, Op. cit.

37. Bergles, A.E., M.K. Jensen, E.F.C. Sommerscales, and R.M. Manglik. 1991. "Literature

Review of Heat Transfer Enhancement Technology for Heat Exchangers in Gas-Fired

Applications." GRI-91/0146, Gas Research Institute, Chicago, Illinois.

38. Beckermann, C. and V.W. Goldschmidt. 1986. "Heat Transfer in the Flueway of Water

Heaters." ASHRAE Transactions 92(2): 485-495.

39. Gas Research Institute, 1993, pp.45-47, Op. cit.

40. Max Minniear, "Initial Estimates of Manufacturing Costs and Energy Consumption", Task

1 of subcontract 6466797, p.3, Minniear Corporation, Panama City, Florida, Nov 1997

41. Max Minniear, Feb. 25, 1998, Op. cit.

42. Jack Langmead, Water Heater Flammable Vapor Ignition Prevention Consortium, DOE,

April 2, 1998, Op.Cit.

43. LBNL Water Heater Database, 1998, Op. cit.

EE-RM-97-900 COMMENT 38TT
99

44. LBNL Water Heater Database, 1998, Op. cit.

45. Paul, D.D., Shepard W.J., Whitacre, G.R., Fischer R.D., Rutz A.L., Locklin D.W., Crisafulli

J.J., Stckford G.H., Murray J.G., Landstrom D.K., Talbert S.G., Buhr A.R., Assessment of

Technologyfor Improving the Efficiency ofResidential Gas Water Heaters. prepared for Gas

Research Institute GRI-91/0298, Battelle Memorial Institute, Columbus, OH, December

1991, Table 8.1, page 96.

46. U.S. Census Bureau; "Consumer Price Index-All Urban Consumers ;" April 1998,

<http://www.census.gov/146.142.4.24/cgi-bin/survymoct>

47. Paul, D.D., et al,., GRI-91/0298, Appendix C, Op. cit.

48. Paul, D.D., et al., GRI-91/0298, Table B.10, Op. cit.

49. Paul, D.D., et al., GRI-91/0298, Appendix D., Op. cit.

50. Technical Support Document: Energy Efficiency Standards for Consumer Products: Volume

1, Appendix D, page D-2, DOE, November 1993

51. Department of Energy, Annual Energy Outlook 1998 (AE098), 1997, Op. cit.

52 Product literature from John Wood (GSW) Water Heaters, received from John Wood on

4/27/1998 and Bock Water Heaters product catalog.

53. Bock Water Heaters product catalog, 1998.

61. John Grahm at R. W. Beckett Corporation, personal conversation, May 16, 1998.

62. Dave Nelsen, Education Chairmen of NAOHSM (National Association of Oil Heating

Service Managers), personal conversation, April 16, 1998.

63. Max Minniear, "Initial Estimates of Manufacturing Costs and Energy Consumption", Task

1 of subcontract 6466797, p.3, Minniear Corporation, Panama City, Florida, Nov 1997

65. Eugene West, "Oil Fired Water Heaters, Improvement to the Energy Use Attribute", received

by PNNL on August 14, 1998.

66. GAMA Cost Data, recieved by LBNL on July 17, 1998

67. Eugene West, "Oil Fired Water Heaters Increased Insulation Thickness - Analysis of Fixed

Cost to Implement". received by PNNL on September 9. 1998

EE-RM-97-900 COMMENT 38TT
100

68. Eugene West, "Oil Fired Water Heaters, Improvement to the Energy Use Attribute". Op.

cit.

69. John Grahm at R. W. Beckett Corporation, personal conversation, September 25, 1998.

70. Survey of residential oil-fired equipment dealers conducted by PNNL during April, 1998.

EE-RM-97-900 COMMENT 38TT
APPENDIX A: "WATSIM-DOE TEST.XLS" - SPREADSHEET TOOL TO

DETERMINE THE ENERGY PERFORMANCE

CHARACTERISTICS OF ELECTRIC STORAGE WATER

HEATERS BASED ON OUTPUT FILES FROM THE WATSIM

COMPUTER SIMULATION MODEL

This Appendix describes the spreadsheet tool "WATSIM-DOE Test.xls", which was developed to

calculate the energy efficiency characteristics according to the specifications of the DOE test

procedure from a standard WATSIM output file. This tool can be found on DOE's Office of Codes

and Standards' web-site (www.eren.doe.gov/buildings/codes_standards/index.htm).

Background

The WATSIM electric water heating simulation program contains two simulation algorithms: one

for the detailed simulation of the energy performance of water heater tanks and a second for

controlling water draw profiles for use with the tank model. The output of WATSIM does not

however include EF, RE, and UA values, which are specific to the DOE test procedure.

Since the simulation analysis must be performed according to the requirements of the DOE

test procedure', the water draw profile is specified to 64.3 gallon (243.4 liter) level. The specified

draw profile is provided in a standard WATSIM draw file (machine.643). WATSIM provides

detailed temperature profiles for the water in the water heater tank during the simulation run. The

temperature profiles are specified in the WATSIM input file (baseline.dat). The draw file and input

file are available in the same DOE's Office of Codes and Standards' web-site. The temperature

profile is provided in a standard WATSIM output file called tw_vs_tl.out. These temperature

readings are used by the "WATSIM-DOE Test.xls" to determine EF, RE, and UA.

"WATSIM-DOE Test.xls" was developed using Microsoft Excel and is a workbook file

consisting of three individual worksheets: 1) results, 2) tw_vs_tl, and 3) EF calc. (Note that at the

bottom of the screen view are the names of all three individual Worksheets.) This is a customized

analysis tool, developed specifically for this analysis and, as such it has certain limitations,

descriptions of which are provided in the detailed explanation of the procedure.

Program Description

Introduction. The following requirements must be satisfied before performing the procedure:

1) "WATSIM-DOE Test.xls" works in conjunction with the standard WATSIM output file

twvstl.out. The two files need to be in the same directory.

2) The tool is customized to work with a set of parameters required by the DOE test

procedure. It is necessary to supply values for the following variables used for the actual simulation:

A-I

EE-RM-97-900 COMMENT 38TT
* water heater rated input, V,,

* average inlet water temperature, Ti,,n,

average ambient temperature during the total standby period, Tstb,,,

* average ambient temperature after the last draw to the end of the 24-hour test, Ts,stb.

The input cells for those variables are located in the twvstl worksheet.

"Results" Worksheet. The purpose of the "results" worksheet is to load WATSIM's tw vs tl.out

file into the spreadsheet tool. The user simply needs to "click" on the Load Data File button to

activate a macro, which loads the tw_vs_tl. out file into the spreadsheet tool. Figure A. shows an

_ 9 A l " *#2A~Ikf~4~w%-~l

'3 J· _ X.L* - ·$ 

21

2¥

Mi bjl ms.sf M - I 'tF

29- i

16 ..

240

Figure A.1 Excel Screen View of Results Worksheet

Excel screen view of the spreadsheet tool's results worksheet.

A-2)

EE-RM-97-900 COMMENT 38TT
"tw vstl" Worksheet. After the tw_vs_tl.out file is loaded into the spreadsheet tool, the user is

automatically transferred over to the twvs_t] worksheet. The twvstl worksheet is where the

tw_vs_tl.out file is actually loaded. Because the twvstl worksheet will contain a previously

loaded twvstl.out file, the user will need to edit the worksheet after the current twvstl. out file

is loaded. Editing consists of clearing out the data from the previous file. Figure A.2 shows a partial

Excel screen view of the spreadsheet tool's tw_vs_tl worksheet. It shows the data that is provided

in WATSIM's twvstl.out file.

* Column A provides the DAY on which data is being recorded. Since the DOE simulated

use test lasts 24 hours, a value of 1 is always recorded.

* Column B provides the TIME (in minutes) when data is being recorded. Since the DOE

simulated use test lasts 24 hours, the last value in which data will be recorded is at the

1440 th minute. Obviously, all the data up the 1440th minute cannot be shown in Figure

A.2 as hundreds of data records are contained in any single tw_vstl.out file.

* Column C provides the water DRAW (in gallons per minute) at the time the data is being

recorded. Since the draw pattern is conducted per the requirements of the DOE simulated

use test, the value recorded will either be 3 gpm or 0 gpm. It should be noted that during

the water draw period, WATSIM records data into the tw_vstl.out file approximately

every 5 seconds. Thus, during the six draw periods lasting approximately 3 Vz minutes as

prescribed by the DOE simulated use test, a wealth of data will be recorded.

* Column D provides the rate of electrical HEATER consumption (in Btu/hr) at the time

in which data is being recorded. In Figure A.2, results are provided for a 50-gal (190-liter)

electric storage water heater with two 4.5 kW electrical heater elements. Thus, in the case

shown in Figure A.2, the rate of electrical heater consumption will always be 15,370

Btu/hr (4.5 kW) when the heater element is required to come on to maintain the

temperature setpoint. It should be noted that during a non-water draw period while the

heater element is on, WATSIM records data into the tw_vstl. outfile approximately every

33 seconds. At conditions where there is no water draw and the heater element is off,

WATSIM records data into the tw_vs_tl.out file approximately every 5 minutes.

* Columns E through AB contain the HOT WATER TEMPERATURE profile data. For

example, Temperature #1 corresponds to the temperature measurement taken closest to

the bottom of the tank while Temperature #24 corresponds to the measurement taken

closest to the top of the tank. Temperature #24 is assumed to equal the temperature of the

hot water drawn from water heater. Temperature #24 is also referred to as the

DRAWTEMP. The 24 temperatures are measured at evenly spaced intervals throughout

the tank.

A-3

EE-RM-97-900 COMMENT 38TT
Ljife tdit D¶ew tnet Faw"t lcds &ata MMidow tx 4ii

:Aja. 9 - E U. ff S 3S g % ,F « i I? ? j " * t * i a .'u; ..

-e ill ~ S%. t~s~I1~W1 I-PA 1 .I;' I -AY MT¶.TrRXv H?-F= HT WAIFf TF.MAPFRAT1F1FS

14 (r)fMi (170T,1mni' »* f2 4}3 4 05 06 *7 0 »9 13 *It *1 413 014 *15 0I- *I »8 'i » 20 021' 22 i 02 $

4. 1 C 3 0 X3 92 IX 135 135 1 X 135 135 13 135 135 135 135 13S 135 135 136 135 135 135 135 135 135 135

5 1 C j u i 2J 12U 1 '. J 12U I 135 136 536 136 13 135 136 136 13 136 136 13S 136 136 136 136 136 135

8 1 rnI 3 *371'3 1 19 119 119 119 116 134 135 135 13S 135 35 135 -35 135 135 135 135 135 (3I 135 135 135 135

7 1 n;f 3 7r 7 17 117 117 1717 117 117 132 35 135 135 135 t35 135 125 435 135 13 435 35 135 135 13535 135 135

8 1 C 3 53,O '1 16 116 116 i 11 30 135 135 1:35 13 135 135 1365 13 135 135 1365 3 335 135 3 35

9 I C c 3 '370 'is15 115 1 51 I1I 116 115 129 134 13 35 135 135 13 136 135 135 135 13S 135 135 1¶ 3 5 135 S 135 135

10; 1 C '57 3 I i 1170 I 11 1 13 I1 11 127 134 135 135 135 135 135 1:5 135 135 135 I35 135 135 135 135 135 135

II ( n, 3 *S '1 1' 11 112 112 112 11 125 133 13 5 13 35 35 135 135 ¶ 135 13 1 3535 135 1 135 135 135 135

.; 1 V-- 3 SS'**U 'II *n I111I1 11"i 11 123 132 135 135 135 1365 13 15 135 135 136 135 135 135 135 135 I

1

3. 136

13! 1 ( 77 3 f "I( 4 1 IM 1C13r'n9¶ 101 I- 121 It? 1¶ 1 135 135 135 135 115 5 1 1 3 15 135 ¶ 135 135 ¶35 1315

14 I C?7 3 '537 01* 100 I CC 100 100 1 ) 119 130 134 135 135 135 135 1?¶5 136 135 1315 135 135 135 135 135 1 35 135

15 i 1 L '53 UN *U' 1U' 1 1u I7 1U I ? 1'i 129 134 135 1:6 135 135 135 13S 135 135 136 136 13S 136 13S 135 135

16 1 I -F '94i1 'nf in6 If 10ins inls 1)3 15 1fl 1 34 135 13S 1 35 '- I'S 135 1 35 1365 35 135 135 1331 35 13 K 135

17 ¶ 1 V 3 '5I70' *'0 105i 10 10'5 10 I35 113 127 ¶33 135 135 135 135 135 135 135 136 135 135 t35 135 135 135 135

18 1 12 1 3 '5370 04 104 104 104 104 134 I1i 125 132 135 135 135 135 165 '35 135 135 135 135 135 135 135 135 135

19i 1 1m 3 '6370 '03 103 103 103 103 103 109 123 132 134 135 135 135 135 135 135 135 135 135 135 135 135 135 135

20 1 14! 3 '5370! '01 102 1 02 102 102 102 107 121 131 134 135 135 135 135 435 135 135 135 135 ¶35 135 135 135 135

21j 1 1.6 3 .5370 "02 102 1¶02 102 102 ¶1I. 02I 119 2IX 134 135 3 135 1 165 35 '35 3 135 135 135 135 135 135 135

22 1 153 3 I5531U 'U1 101 101 101 101 11 101 117 129 133 135 135 135 135 135 135 135 135 13 136 135 135 135 135

23 ¶ 1 71 3 -i 15771 n 100 ion 0 iwoi 1 1) I 1) 115 12 133 131 1i35 135 135 '35 135 135 35 135 135 135 135 13S 16

24 i 117 3 '5370J X.7 997 997 99.7 997 997 997 113 127 133 134 ¶35 135 135 135 1365 ¶3 136 135 1333 6 135 135

26 1 1 3/ 3 $3j/U 9- 49Y' 99.1 99 1 991 99 I ¶3111 125 132 124 135 135 135 ' 35 135 136 135 135 135 135 135 ¶35 . 135

2. 1 i 3 :f53n as 91 84 <W14 i,4 9R4 9A14 934 109 124 131 134 135 135 I3S 13S 135 136 13S 135 1-3 135 135 135 1.S

2I 1 i2 3 55370 37 3 979 970 9789 78S 970 978 107 123 131 134 135 135 135 13 35 15 135 '3 135 1 35 135 135 135 135

26 1 ¶2 3 '5370 372 97'2 972 972 972 972 972 105 121 130 134 135 135 1¶S 13 1335 135 135 135 ¶3S 135 135 135 135

29 I 2 1 3 '53701 5 9E 6 96 96 96W 966 966 6 956 103 119S 129 133 135 135 135 535 135 135 135 135 13 135 1 5 136 135

30 2I ' 3 '5370! 9 3 959 959 959 959 959 359 101 117 129 133 135 135 135 135 135 136 135 135 135 135 135 13- 135

31 1 24 3 163701 3 .153 95. 9.3 9633 959 9.3 995 ¶15 127 132 134 135 ¶S 13- 135 135 13 3 135 131 35 136 35 ¶35 135 3,2 1 ;4 3 5370 -3 948 948 394 948 94 948 977 113 126 132 134 135 135 135 135 135 135 135 135 135 135 135 135

33 1 5, 1 '970'j C 4I 943 943 9449 3 94 3 8 ¶11 174 131 134 1 I5 135 35 35 13 135 35 1 135 15 136 1.'s 135 135

34 1 ?7 3 '5370 93 03893 938 93.8 938 93.6 93.8 94.5 1C 3 123 131 134 135 135 135 135 135 135 135 135 135 135 I35 135

3l 1 -4 3 9537IJ 33 93.3 93 93.3 93.3 93 933 933 6 1307 122 130 133' 135 156 135 135 165 135 135 13 135 135 135 135

2316' \ 167 9 3ri 9S); 929 979 929 929939 929 93 105 120 1219 133 135 I 135 135 135 135 135 3 1 135 135 1135 135

37 1 2 3 '*3701 25 92s.5 925 925 925 92 S 925 925 I 119 128 133 134 13S 35 135 135 135 135 135 135 135 135 35

380 1 .' 'S53Uj 92 9 V2 92 92 92 92 92 921 ¶l1 1? 127 132 134 135 '35 135 13S 135 135 ¶3 13 135 13. 135 3 1 ?37 3 '5370; ? 5 916 916 916 916 916 916 917 99.3 115 16 132 134 1735 135 135 1135 135 I 135 113 135

144 ''\lw m v»_tl/¶cat/res V s C. / 'w . r 

Dv4 * o *ME \ ^ 0 C 0 Mn 

c e aj y.* * *e **-* "*- -- *--- ****---- --***- *-- **** "*-* "*- * *--* - -*

Figure A.2 Excel Screen View (1 of 2) of twvstl Worksheet: tw vstl.out Variables

A-4

EE-RM-97-900 COMMENT 38TT
i t *J e tdit vew Insrrt ,Pwrat als tr w t.__,* , _ aui 

rAil"* o - 5s 'TisjA . *^ f g. ^ m 9.. J . ._|: -,-~ ? " -!:~ ; O ^-~: :^ 

\_^J"B\"C .';'AC ."t - 3^.1. .AE U:..NU ..../.A... j. ..... *P.. ...... 0, .ij:1 .i.. .lAi.".lt.

tA, ' t r » .t4 T* . fE nl. r nrn »n m H I -.mnf H·.*II Si- r Slm H".F Sum TI1EMTlF t1WFFP'

2 C 1 IMIJI Temp Coinl, Cci 2 Coumt2 :crt 1r Co. I ount2 Cournt Co 1 IPcl et MEANTEMr -

3 .'FA\TFmP nra r rC ' rn A Hr- HCB ' ' F-r ,n , HC ^ ' Mf 1n Fi rvf Twr r

4 1 13142 1 I 1 0 0 0 0 0 0 O0

5 , I L J 1Jt 2U C U U I I 1 1 0 0 2 262

1 C I 13076 C 0 0 1 0 0 0 1 0 009 11.77

7 1 0. 130 20 0 0 0 0 0 1 0 0 C 11.73

8 1 C.-l 12982 C 0 0 0 0 0 I 0 0.0 11 e8

9 1 C 3 129 34 C 0 0 1 0 0 1 0 009 1164

10 1 4E 1 26: 3 0 0 0 1 0 0 0 1 0 0.1 128

11 I 5. 12834 0 0 0 0 0 1 0 0.1 1283

12 C : 1b r c (1 1 a B 0 1 0 0.1 12.lg

1a I r77 1 ?J 4 e 0 I 0 n I 0 0O . 1147

14 1 C 7 12 96 0 0 0 I 0 0 0 1 0 01 1270

15 1 1 126' U U J I 0 0 0 1 0 OM9 11 39

16 1 1-f 1inqfl r 0 n O I n 0 0 1 1231

17 1 I1C 125 6 C 0 0 0 0 0 1 0 009 11 31

18 1 1 12523 0 0 1 0 0 0 1 0 0.1 1252

19 1 1 12 479 0 0 0 I 0 0 0 1 0 01 1248

1 1 4f 12437 C 0 I 0 0 0 I 0 0.1 1244

21 1 1. 12380 0 0 0 o0 0 0 1 0 0.11 1362

22 1 16 12353 3 0 0 0 0 0 0 1 0 0o07 865

23 1 71 21?217 0 0 0 1 0 0 0 1 0 n00 9q

24 179 122 98 0 0 0I 0 0 1 0 O.t 9 e4

5 1 1' . 12' C3 0 U 1 U 0 0 1 0 0 d 9 2

2' I Y 1??43 0 n 0 I n . n 1 0 ao.e q97

27 1 2 4 12216 C 0 0 0 t 0 10 009 99

28 1 121871 C 0 0 0 0 1 0 0 975

29 21 121 57 C 0 0 I 0 0 I 0 009 10 s

30 1 2 121 22 0 0 0 1 0 0 0 1 0 009 10.91

31 ' 4 12088 0 0 0 I 0 0 0 1 0 0.1 12 9

32 1 :4- 121055 0 0 I 0 0 0 1 0 009 10

t3 1 i 1n702? 0 n n I 0 0 0 I 0 oo00s ne?

34 1 ;7 1'9988 0 0 0 1 0 0 0 1 0 0J09 10.79

35 /I 1' 55 O U O I O 0 a 1 0 007 8.37

. 1 , 1' i ?q4 0 n D I 0 o o 1 o o0O0 954

37, 1 2c 1'090 C 0 0 0 0 0 1 0 009 951 38' 1 . '152 Li 0 U I U a 1 0 0 8 .48

39 1 3 7 1'e 15 C 0 0o 0 0 0 I o 0C 106I3

14 4 \_Wvstl I /EF cc reaJts / --. . t - A-.-

D · toSi eo \ \ a O #^ B - i^ ,-l *4I -' g| . i ;0 ; ^ ^

Pea, adv - -"*r--*- "** - -; - --*- -- 7- 

Figure A.3 Excel Screen View (2 of 2) of twvstl Worksheet: Calculated Variables

A-5

EE-RM-97-900 COMMENT 38TT
Figure A.3 shows the remaining variables in the tw_vs_tl worksheet. The remaining

variables are NOT recorded by WATSIM into the tw_vstl. out file. Rather, they are variables which

are automatically calculated in order to determine quantities necessary for establishing the EF, RE,

and UA of the water heater being analyzed according to the DOE test procedure. Figure A.3 presents

a partial Excel screen view of the spreadsheet tool's twvs_tl worksheet showing the calculated

variables.

* MEANTEMP is located in column AC. It represents the mean hot water tank temperature

and is based on 12 of the 24 temperatures recorded in Columns E through AB. The

following equation shows how MEANTEMP is calculated.

T2+ T3 T 6+ T7 T o+ 0 T 11 T 14+ T5 T 18+ T,9 T 22+ T 23

Tmean- 2 + 2 + 2 2

6

Since the DOE test procedure requires that six temperature readings be used to establish

the mean tank temperature, those temperatures recorded in tw_vs_tl. out that best represent

the six temperatures (the average of the two temperatures representing the six evenly

spaced regions of the tank) are used to calculate MEANTEMP.

* DCA is located in column AD. DCA returns a value of 1 only if the row DRAW changes

from a value of 0 to 1.

* DCB is located in column AE. DCB is 1 whenever DRAW changes value (either going

from a value of 0 to 1 or 1 to 0). Thus, a value of 1 will be calculated for DCB only at the

beginning and end of each water draw period.

* DCC is located in column AF. DCC sums up the values in column AE (variable DCB)

if and only if DCB equals a value of 1 and DRAW changes value. Thus, a value of 1 or

greater will be calculated for DCC only at the beginning and end of each water draw

period. For example, during the first draw period, DCC will equal a value of 1 at the

beginning of the draw and a value of 2 at the end of the draw. During the second draw

period, DCC will equal a value of 3 at the beginning of the draw and a value of 4 at the

end of the draw. DCC gets incremented by a value of 1 for each subsequent draw.

* DCD is located in column AG. DCD changes to an incrementally larger value for the

length of each of the six draw periods. For example, DCD is a value of 1 during the length

of the first draw period, a value of 2 during the length of the second draw period, a value

of 3 during the length of third draw period, and so on for each subsequent draw period.

* HCA is located in column AH. HCA is comparable to variable DCA except that its value

is based on the status of HEATER rather than DRAW. HCA changes to a value of 1 only

A-6

EE-RM-97-900 COMMENT 38TT
when HEATER changes from a value of 0 to 1.

* HCB is located in column AI. HCB is comparable to variable DCB except that its value

is based on the status of HEATER rather than DRAW. HCB switches to a value of 1

whenever HEATER changes value (either going from a value of 0 to 1 or 1 to 0). Thus,

a value of 1 will be calculated for HCB only at the beginning and end of each time period

in which the heater element is on.

* HCC is located in column AJ. HCC is comparable to variable DCC except that its value

is based on the status of HEATER rather than DRAW.

* HCD is located in column AK. HCC is comparable to variable DCC except that its value

is based on the status of HEATER rather than DRAW. HCD changes to an incrementally

larger value for the length of each time period that the heater element is on. It should be

noted that, unlike the water draw periods, there may be more than six time periods in

which the heater element comes on. The heater element comes on to maintain

temperature setpoint, thus, it cycles during standby operation after all six water draws

have been completed. For example, a typical baseline 50-gal (190-liter) electric water

heater will have its heater element cycle 9 to 10 times in the course of the 24-hour DOE

simulated use test.

* HCF is located in column AL. HCF switches to a value of 1 and remains a value of 1

after the heater element has cycled for sixth time.

* TIMEDIFF is located in column AM. TIMEDIFF tracks the time difference between each

set of recorded data.

* TDIFF_TEMP is located in column AN and is used to calculate "time-weighted average"

mean tank temperatures. Because the time difference between data records varies

depending on the status of the water DRAW and the HEATER elements, the mean tank

temperature for a time period spanning multiple water draws cannot be determined

directly from the values calculated for MEANTEMP. TDIFF_TEMP allows for the

determination of accurate mean tank temperatures. TDIFF_TEMP is calculated by

multiplying TIMEDIFF by MEANTEMP. Thus, for any desired time period, the mean

tank temperature is determined by summing the values for TDIFF_TEMP and dividing

by the elapsed time for the time period.

A-7

EE-RM-97-900 COMMENT 38TT
"EF calc" Worksheet. This worksheet shows the results of the procedure. After all of the data has

been loaded and intermediate values generated in the tw_vstl worksheet, the user must manually

switch to the EF calc worksheet to see the results of the energy performance calculations. All the

energy performance calculations in the EF calc worksheet, including those for EF, RE, and UA,.are

done automatically. Figure A.4 shows the energy performance values as they are presented in the

EF calc worksheet. All the variables in the EF calc worksheet are required by the DOE test

procedure equations in order to determine RE, UA, and EF. The EF calc worksheet uses the same

nomenclature as in the DOE test procedure in order to maintain consistency and to enable the user

to easily identify and define all the variables.

All shaded areas in the EF calc worksheet represent variables that are determined directly

from the data in the twvstl worksheet. All other variables are determined from DOE test

procedure equations or are equal to default values provided in the test procedure. A list of variables

in the EF calc worksheet determined from the data in twvstl worksheet is provided below.

* M,, mass of water withdrawn during the first draw (lbm): Determined by multiplying the

DRAW rate (3 gpm) during the first draw by the elapsed time of the first draw. Once the

total draw is determined in gallons, it is converted to lbm using conversion factors. The

calculation is based on the use of variable DCC in the twvstl worksheet. The TIME

when DCC equals 1 (the beginning of the first draw) is subtracted from the TIME when

DCC equals 2 (the end of the first draw) in order to calculate the elapsed time.

* Tde,1, average delivery temperature for the first draw (°F): Determined by calculating the

average draw temperature during the first draw. The calculation is based on the use of

variable DCD in the twvstl worksheet. First, all the DRAWTEMPs (hot water

temperature #24) for the period when DCD equals 1 (the length of the first draw) are

summed. Then, the summed DRAWTEMP value is divided by the number of times in

which DCD equals 1 to arrive at the average delivery temperature during the first draw.

* Tmax, maximum mean tank temperature recorded after cutout following the first draw

(°F): The key to to determining Tm.,, is selecting the maximum temperature after the

HEATER element first cycles off. This determination is based on the use of variable

HCC in the twvstl worksheet. Since the maximum temperature occurs immediately

after the HEATER element cycles off, the value for the maximum MEANTEMP is when

HCC equals 2 (the end of the first HEATER cycle).

* To, maximum mean tank temperature recorded prior to the first draw (°F): This is simply

the first value for MEANTEMP recorded in the twvs_1 worksheet.

* Qr, total energy used by the water heater between cutout following the first draw,

including auxiliary energy such as pilot lights, pumps, fans, etc. (Btu): Determined by

multiplying the HEATER's rate of consumption (15,370 Btu) during its first cycle by the

elapsed time of the HEATER's first cycle. Key to determining Qr is the calculation of

the elapsed time of the first HEATER cycle. The calculation is based on the use of

A-8

EE-RM-97-900 COMMENT 38TT
variable HCC in the tw_vs_tl worksheet. The TIME when HCC equals 1 (the beginning

of the first cycle, i.e., when the HEATER element first turns on) is subtracted from the

TIME when HCC equals 2 (the end of the first cycle, i.e., when the HEATER element first

turns off) in order to calculate the elapsed time.

Qsby, total energy consumed by the water heater between the time at which the maximum

mean tank temperature is observed after the sixth draw and the end of the 24-hour test

period (Btu): Determined by calculating the total HEATER energy consumption during

the standby period of the water heater. The standby period, with respect to calculating

Qtby starts immediately after the sixth cycle of the HEATER element. This is because the

maximum mean tank temperature occurs immediately after the HEATER element cycles

off for the sixth time. Key to determining Qtby is the calculation of the elapsed time of

each HEATER cycle after the HEATER element's sixth cycle. The calculation is based

on the use of variable HCC in the twvstl worksheet. At the TIME when the HEATER

cycles off for the sixth time, HCC equals 12. Thus, the elapsed time of the seventh

HEATER cycle is determined by subtracting the TIME when HCC equals 13 (the

beginning of the seventh cycle) from the TIME when HCC equals 14 (the end of the

seventh cycle). The elapsed times of all subsequent cycles are determined in the same

manner with the beginning and ending HCC values for each cycle incremented by 1.

Once all the elapsed times are determined, they are summed and then multiplied by the

HEATER's rate of consumption to come up the total HEATER energy consumption

during the standby period.

T24, mean tank temperature at the end of the 24-hour test period (°F): This is simply the

value for MEANTEMP corresponding to the last record in the tw_vs_l worksheet (i.e.,

when TIME equals 1440).

* T,,, maximum mean tank temperature observed after the sixth draw (°F): Key to

determining T,, is selecting the maximum temperature after the HEATER element cycles

off for the sixth time. This determination is based on the use of variable HCC in the

tw_vstl worksheet. Since the maximum temperature occurs immediately after the

HEATER element cycles off, the value for the maximum MEANTEMP is when HCC

equals 12 (the end of the sixth HEATER cycle).

* tstby,, elapsed time between the time at which the maximum mean tank temperature is

observed after the sixth draw and the end of the 24-hour test period (hours): Very similar

to determining Ts. Key to determining tstby, is selecting the maximum temperature after

the HEATER element cycles off for the sixth time. This determination is based on the use

of variable HCC in the tw_vs_tl worksheet. Since the maximum temperature occurs

immediately after the HEATER element cycles off, the value for the maximum

MEANTEMP is when HCC equals 12 (the end of the sixth HEATER cycle). The TIME

corresponding to when HCC equals 12 is subtracted from 1440 (the TIME at the end of

the test period) to arrive at the elapsed time.

A-9

EE-RM-97-900 COMMENT 38TT
* Tstby, average storage tank temperature between the time at which the maximum mean

tank temperature is observed after the sixth draw and the end of the 24-hour test period

(°F): Key to determining Tstby is selecting the maximum temperature after the HEATER

element cycles off for the sixth time. This determination is based on the use of variable

HCF in the twvstl worksheet. Since the maximum temperature occurs immediately

after the HEATER element cycles off, the value for the maximum MEANTEMP is when

HCF equals 1 (the end of the sixth HEATER cycle). HCF remains a value of 1 for the

remainder of the 24-hour test period. For time period when HCF equals 1, the sum of the

TDIFF_TEMP values and the sum of the TIMEDIFF values are calculated. The average

storage tank temperature is determined by dividing the sum of the above TDIFF_TEMP

values by the sum of the above TIMEDIFF values.

* M2, mass of water withdrawn during the second draw (Ibm): Determined by multiplying

the DRAW rate (3 gpm) during the second draw by the elapsed time of the second draw.

Once the total draw is determined in gallons, it is converted to lbm using conversion

factors. The calculation is based on the use of variable DCC in the twvstl worksheet.

The TIME when DCC equals 3 (the beginning of the second draw) is subtracted from the

TIME when DCC equals 4 (the end of the second draw) in order to calculate the elapsed

time.

* Tde, 2, average delivery temperature for the second draw (°F): Determined by calculating

the average draw temperature during the second draw. The calculation is based on the use

of variable DCD in the twvstl worksheet. First, all the DRAWTEMPs (hot water

temperature #24) for the period when DCD equals 2 (the length of the second draw) are

summed. Then, the summed DRAWTEMP value is divided by the number of times in

which DCD equals 2 to arrive at the average delivery temperature during the second draw.

* M3, mass of water withdrawn during the third draw (Ibm): Determined by multiplying the

DRAW rate (3 gpm) during the third draw by the elapsed time of the third draw. Once

the total draw is determined in gallons, it is converted to lbm using conversion factors.

The calculation is based on the use of variable DCC in the twvs_t] worksheet. The

TIME when DCC equals 5 (the beginning of the third draw) is subtracted from the TIME

when DCC equals 6 (the end of the third draw) in order to calculate the elapsed time.

Tde, 3, average delivery temperature for the third draw (°F): Determined by calculating the

average draw temperature during the third draw. The calculation is based on the use of

variable DCD in the twvstl worksheet. First, all the DRAWTEMPs (hot water

temperature #24) for the period when DCD equals 3 (the length of the third draw) are

summed. Then, the summed DRAWTEMP value is divided by the number of times in

which DCD equals 3 to arrive at the average delivery temperature during the third draw.

M4, mass of water withdrawn during the fourth draw (Ibm): Determined by multiplying the

DRAW rate (3 gpm) during the fourth draw by the elapsed time of the fourth draw. Once

the total draw is determined in gallons, it is converted to Ibm using conversion factors.

A-10

EE-RM-97-900 COMMENT 38TT
The calculation is based on the use of variable DCC in the twvstl worksheet. The

TIME when DCC equals 7 (the beginning of the fourth draw) is subtracted from the TIME

when DCC equals 8 (the end of the fourth draw) in order to calculate the elapsed time.

Tde,4, average delivery temperature for the fourth draw (°F): Determined by calculating

the average draw temperature during the fourth draw. The calculation is based on the use

of variable DCD in the twvstl worksheet. First, all the DRAWTEMPs (hot water

temperature #24) for the period when DCD equals 4 (the length of the fourth draw) are

summed. Then, the summed DRAWTEMP value is divided by the number of times in

which DCD equals 4 to arrive at the average delivery temperature during the fourth draw.

* Ms, mass of water withdrawn during the fifth draw (lbm): Determined by multiplying the

DRAW rate (3 gpm) during the fifth draw by the elapsed time of the fifth draw. Once the

total draw is determined in gallons, it is converted to Ibm using conversion factors. The

calculation is based on the use of variable DCC in the twvstl worksheet. The TIME

when DCC equals 9 (the beginning of the fifth draw) is subtracted from the TIME when

DCC equals 10 (the end of the fifth draw) in order to calculate the elapsed time.

* Tdel5, average delivery temperature for the fifth draw (°F): Determined by calculating the

average draw temperature during the fifth draw. The calculation is based on the use of

variable DCD in the twvs tl worksheet. First, all the DRAWTEMPs (hot water

temperature #24) for the period when DCD equals 5 (the length of the fifth draw) are

summed. Then, the summed DRAWTEMP value is divided by the number of times in

which DCD equals 5 to arrive at the average delivery temperature during the fifth draw.

* M6, mass of water withdrawn during the sixth draw (lbm): Determined by multiplying the

DRAW rate (3 gpm) during the sixth draw by the elapsed time of the sixth draw. Once

the total draw is determined in gallons, it is converted to lbm using conversion factors.

The calculation is based on the use of variable DCC in the twvstl worksheet. The

TIME when DCC equals 11 (the beginning of the sixth draw) is subtracted from the TIME

when DCC equals 12 (the end of the sixth draw) in order to calculate the elapsed time.

* Tde,6, average delivery temperature for the sixth draw ( F): Determined by calculating the

average draw temperature during the sixth draw. The calculation is based on the use of

variable DCD in the twvstl worksheet. First, all the DRAWTEMPs (hot water

temperature #24) for the period when DCD equals 6 (the length of the sixth draw) are

summed. Then, the summed DRAWTEMP value is divided by the number of times in

which DCD equals 6 to arrive at the average delivery temperature during the sixth draw.

* Q, total energy used by the water heater during the 24-hour simulated use test including

auxiliary energy such as pumps, fans, etc. (Btu): Determined in a very similar manner to

Qstby. Key to determining Q is the calculation of the elapsed time of each HEATER cycle

in the 24-hour test period. The calculation is based on the use of variable HCC in the

twvstl worksheet. The variable HCC increments by a value of 1 each time the

A- I

EE-RM-97-900 COMMENT 38TT
HEATER turns on and off. Thus, for the first HEATER cycle, HCC equals 1 when the

HEATER turns on and increments to a value of 2 when the HEATER turns off. For each

subsequent HEATER cycle, the value of HCC increments by 1. Thus, the elapsed TIME

of any given cycle is determined by subtracting the TIME corresponding to the

"beginning" HCC value for that cycle from the TIME corresponding to the "ending" HCC

value for the same cycle. The "beginning" HCC value for any cycle will have an odd

numerical value while the "ending" HCC value will have an even numerical value. Thus,

if the HEATER cycles ten times in a 24-hour period, the "beginning" HCC value will

equal 19 and the "ending" HCC value will equal 20. Once the elapsed times of all

HEATER cycles are determined, they are summed and then multiplied by the HEATER's

rate of consumption to come up the total HEATER energy consumption during the 24-

hour test period.

* Tby, mean tank temperature during the total standby portion of the 24-hour test (°F):

Determined by calculating the average mean tank temperature whenever a DRAW is not

occurring. This determination is based on the use of variable DCD in the tw_vs_tl

worksheet. Whenever DCD equals 0 (i.e., when a DRAW is not occurring), the sum of

the TDIFFTEMP values and the sum of the TIMEDIFF values are calculated. The

average mean tank temperature is determined by dividing the sum of the above

TDIFF_TEMP values by the sum of the above TIMEDIFF values.

* tby2, the number of hours during the 24-hour simulated test when water was not being

withdrawn from the water heater (hours): Determined by calculating the elapsed times

between DRAWS and the elapsed time between the end of the last (sixth) DRAW and the

24-hour time period. This determination is based on the use of variable DCC in the

tw_vs_tl worksheet. The TIME when DCC equals 3 (the beginning of the second draw)

is subtracted from the TIME when DCC equals 2 (the end of the first draw) in order to

calculate the elapsed time between the first and second draw periods. For each subsequent

time period between draws, the elapsed time is calculated in the same manner. The TIME

when DCC equals 12 (the end of the sixth draw) is substracted from the TIME at the end

of the 24-hour test period in order to calculate the elapsed time between the end of the 24

test period and the last draw. After all the elapsed times when water is not being drawn

are determined, they are summed to arrive at the value for ttby,2.

A-12

EE-RM-97-900 COMMENT 38TT
RECOVERY EFFICIENCY (n,) CALCULATIONS

M UTd ^, ,., (TdL+Tb, )/2 C T . -p T.Io 0-, l+To)/2 C2 Qt |i n,

lb, F F F Bht/lb, F F F F Bhi/lb,-F gal lb ,/gal Btuj

88.00 135.00 58.00 96.50 0.99 131.42 131.42 131.42 1.00 45.00 8.23 6936.99 0.966

UA CALCULATIONS

Q.,b T -4 T. - (Tz2+T.)/2 t,,t Cp p M Qh T- T, T,- UA

Bnt F F F hours Bh/lb, -F lh/gal lb,, Btu/hr F Bu/hr-F

458.19 132.28 1 31.41- 131.4 18.54 I.OU 8.23 370.13 230.12 130.82 7.0 3.5-3-

PRELIMINARY CALCULATIONS

-T It] I Co M, | 1d2 | L-M^ | Cp |1

Ib,,, F Biv/lb,.-F Ib, F Bhu/lb,-F Ib, F Btu/lb -F

M.W 135.W 1.00 8- 134.60-99 0. V.7.5U0 34.6 U9.YY

rKtLIMIINAKY LALLULA IIJNS

M I I dL I CPS M I U' M -- CP6 lb," F Bhtulb-F 1b, F Bhu/lb,-F lb,, F Bnu/lb -F

| u X7.50 134.60 | .99 - | X.W 134.60 --- - O YY -. | K8.Z4 | 134.60 -|1O.Y

ENEKGY USED ''O HEAI WAI'ER (Qw)- CALCULATIONS

| djl-Tm)/n,l MCp2(TdKr2-T.)1n, MplC3(TrT)n, MC* (I-bn, MnSicpsn(TLkS-nbiln M AC(ln F

/UU7.U6 69U.3 \ I 6863.15 6862.72 --o 0.38 I I 6Y1.15 4, .X | S.M

ENERGY USED '10 HEAI WA'IER IF DELIVERED IEMPERAIURE EQUALS 135'F (QHW.7 ) - CALCULATIO.NS

M,C,,(135-58)/n, M,C,,(135-58)/n, M,C,,(135-58n,7 M ^(4 5-58)/n, MC,^(35-58n, M6C,6(35-5)/n, [| Q h

| 7007.50 | 6Y37.42 689Y.536 689.36 | 0937.4Z 6956.XS 6 6 | 4163.31 

MODIFIED DAILY WATER HEATING ENERGY CONSUMPI'ION (Qd) CALCULATIIONS

| Q | T b T*Y | ta,2 t | Q b | Qdm Bht Bht F I F Bt B h u B

4640 .27 46311.7 1 13U.11 67.0 | 3.64 | 46731.63 | 179.47 4011.1u

ENERGY FACTOR (Er) CALCULATIONS

M,C,,(135-58)/Qd= I MCp,,(135-58)/Qd I M,Cp(135-58YQd= M4Cp(135-58)/Qma MCp(I-58)/Qd MC(- E

0.1i444 0.1430 , 0.142 - 0.142. 0.1143430 -J- 4 " S

Figure A.4 Energy Performance Values as presented in the EF calc Worksheet

A-13

EE-RM-97-900 COMMENT 38TT
References

1. 10 Code of Federal Regulations, Part 430- Energy Conservation Program for Consumer

Products Energy Conservation Program for Consumer Products, Appendix E to Subpart B

- Uniform Test Methodfor Measuring the Energy Consumption of Water Heaters.

A-14

EE-RM-97-900 COMMENT 38TT
APPENDIX B: WATER HEATER ANALYSIS MODEL (WHAM) - METHOD FOR

DETERMINING WATER HEATER ENERGY CONSUMPTION

Introduction

The Water Heater Analysis Model (WHAM) is a simple energy equation that accounts for a

variety of operating conditions and water heater characteristics when calculating energy

consumption. The WHAM energy calculation is based on assumptions that account for a variety

of field conditions and water heater types. The results of WHAM calculations have been

compared to the results of detailed water heater simulation programs and show a high level of

accuracy in estimating energy consumption.

WHAM Algorithm Fundamentals

WHAM, which is based on the DOE water heater test procedure, permits the user to minimally

describe both the water heater and the water heater operating conditions (10CFR430, Subpart B).

The operating conditions are characterized by four variables:

* daily draw volume,

* thermostat setpoint temperature,

* inlet water temperature, and

* ambient air temperature.

The water heater is described by:

* rated input (Pon),

* stand-by heat loss coefficient (UA), and

* recovery efficiency (RE).

The DOE water heater test procedure includes a method for calculating the Energy Factor

(EF), a measure of efficiency. During the standard test procedure, a 24-hour trial is performed in

which 6 equal draws are made during the first 6 hours of the test for a total of 64.3 gallons

(243.4L). For the remaining 18 hours, the water heater is in stand-by mode and associated energy

losses are measured. The energy consumption during the test is totalled and the mass of water

drawn is summed over the six draws. The temperature of the water entering, leaving, and inside

the water heater tank is recorded. The temperature of the air around the water heater is also

noted. Additional equations appear in the test procedure to correct for any deviation from the

standard testing specifications to guarantee uniformity in testing results in different laboratories.

The test is based on the conditions shown in Table 1.

B-l

EE-RM-97-900 COMMENT 38TT
TABLE 1. DOE Test Procedure Operating Conditions

Daily Draw, Thermostat Setpoint Temperature, Inlet Water Temperature, Ambient Air

gallon (liter) °F (°C) °F (°C) Temperature, °F (°C)

64.3 (243.4) 135 (57) 58 (14) 67.5 (49.7)

Stated in general terms, EF is the ratio of the energy output of the water heater to the total

amount of energy delivered to the water heater. EF is the added energy content of the water

drawn from the water heater divided by the energy required to heat and maintain the water at the

water heater's setpoint temperature:

,EF MCp-(tank - Tinier) EF = (1)

Qdm

where:

EF = energy factor

M = mass of water drawn (Ibs) (kg)

C, = specific heat of water, (Btu / lb - °F) (kJ/kg - °C)

Ttank = water heater thermostat setpoint temperature (°F) (°C)

7

Tniet = the inlet water temperature (°F) (°C)

Qdm = water heater's daily energy consumption (Btu) (kJ)

This equation establishes the EF for water heaters. Manufacturers are required by federal

law to determine EF and to label all products with EF. UA and RE are determined in the course

of the test procedure and are used in the test procedure equations to calculate EF.

WHAM is based on a number of assumptions. It assumes that the values for Pon, UA,

and RE do not change significantly when conditions differ from test procedure conditions. Other

assumptions also help to simplify the equation:

* Water temperature in the tank is always at the thermostat setpoint

Water and air temperatures are constant

* Water density is constant

Specific heat of water is constant

WHAM only calculates average energy use. Other tools should be used for calculating

water heaters' response to peak use and for sizing systems.

WHAM Development

B-2

EE-RM-97-900 COMMENT 38TT
WHAM relies on the following variables, which are defined in the DOE test procedure:

Qn = total water heater energy consumption (Btu/day) (kJ/day)

Qrov = energy consumed to heat the water drawn from the water heater (Btu/day) (kJ/day)

Qstdby = energy consumed to make up for standby heat loss from the water heater (Btu/day)

(kWh/day)

Qot = heat content of the water drawn from the water heater (Btu/day) (kJ/day)

Hby = hours of standby for storage water heaters (hr/day)

RE = recovery efficiency

EF = energy factor

Pon = rated input power (Btu/hr) (kJ/day)

UA = standby heat loss coefficient (Btu/hr - °F) (kJ / hr - °C)

Tak = tank thermostat setpoint temperature (°F) (°C)

Tin = inlet water temperature (°F) (°C)

Tmb = temperature of ambient air surrounding the water heater (°F) (°C)

vol = volume of water drawn in 24 hours (gal/day) (liter/day)

den = density of water (Ib/gal) (kg/L)

Cp = specific heat of water (Btu/lb - °F) (kJ/(kg °C)

The amount of energy consumed by the water heater (Qn) includes not only the amount of

energy needed to heat the water (Qcov) but also the amount of energy to replace that which is

lost to the surroundings when no water is being drawn from the tank (Qwby).

Qi Q + Qstdby (2)

By definition, energy consumed to heat the water drawn from the water heater (without

standby losses) is equal to the heat content in the water divided by the RE.

0 = Qou u) (3 Qrecov R(3) n 

Energy consumption to compensate for standby energy loss from a storage tank water

heater is equal to the difference in the water heater thermostat setpoint and the average ambient

air temperature around the water heater multiplied by the standby heat loss coefficient and the

hours of standby. Note that the standby heat loss coefficient is expressed in terms of energy

losses to the environment. The hours of standby are equal to the number of hours the burner is

not firing, plus the number of hours the burner is firing (or elements are energized) to make up

for standby heat losses.

B-3

EE-RM-97-900 COMMENT 38TT
Qstdby = UA '(Tank - Tmb) Hstdby (4)

The hours of standby equals the time the water heater is not recovering from a draw. This

is equal to 24 hours minus the ratio of the amount of energy used to heat the water drawn from

the water heater divided by the rated input power of the water heater.

Qrecov Hstdby = 24- (5) Pon

Heat content of the hot water drawn from the water heater is equal to the volume of water

drawn multiplied by the water's density, specific heat, and the temperature difference between

the water heater setpoint and the inlet water temperature.

Qot = vol-den Cp(Ttank - Tin) (6)

The energy factor is equal to the heat content of the water drawn from the water heater

divided by the total energy consumption.

Q out EF = (7)

Qin

Q i, can be represented by the parameters from the DOE test procedure by substituting for

Qrecov and Qtdby in equation (2):

Qin = QREt + UA 24.'^ -^^ ^-^ -^)-^ (8) (Ttank Tb) 24 RE QPont (8) RE RE.Pon

WHAM can now be expressed by expanding Qu,,, rearranging the terms, and simplifying.

This is the equation to calculate average daily energy consumption.

Q vol den -CP (Tnk - Tn) ( l UA (Ttank - Tamb) 24 UA(T -T ) (9) voldenC'(Tt k- T) Pon an m

The WHAM equation is a function of readily available information that can be grouped

B-4

EE-RM-97-900 COMMENT 38TT
into three categories:

* Physical characteristics of water represented by density and specific heat (Cp)

* Water heater operating conditions represented by draw volume and temperatures

* Water heater parameters represented by UA, RE, and Pon

WHAM: Calculation of Standby Heat Loss Coefficient UA

UA is a necessary input in the WHAM equation, yet it is not always available. The same

DOE test procedure that established a basis for the WHAM equation can be used for determining

a value for UA.

Since energy consumption to make up for standby losses is equal to the total energy

consumption minus the energy content of water withdrawn from the water heater, it is possible to

rearrange equation (2) as follows:

Qstdby = Qin-Qrecov (10)

Substituting for Qn and Qcov from equations (3) and (6), equation (10) becomes:

Qtdby Qit EF RE(11)

The energy consumption to make up for standby losses can also be defined by combining

equations (3), (4), and (5):

Qsdby = UA (Tk- Tb) 24 Pon(12)

Equating the two terms for Qtdby from equations (11) and (12) and solving for UA

produces equation (13):

EF RE U (TAnkTamb) (RE___ (13)

(Tk - T.)- -24 - I

Qout RE-Pon

Inserting the temperatures and conditions specified in the test procedure, the equation

becomes:

B-5

EE-RM-97-900 COMMENT 38TT
UA EF RE] UA= = 24 1 (14)

41094 RE-Pon

This equation allows the user to determine a value for UA, if it is unavailable from other

sources.

WHAM Sample Calculation

A sample application of the WHAM equation to calculate the energy consumption and

the standby heat loss coefficient (UA) is presented in Table 1 and Table 2. The available data is

organized into three sections representing: 1) the inputs for the energy parameters from DOE test

procedure, 2) the operating conditions parameters, and 3) the physical characteristics of water.

The average daily energy input (energy consumption) and the standby heat loss coefficient are

calculated directly from the input data. Detailed definitions of all the parameters can be found in

the DOE test procedure document (see reference 2 of the main report).

C:\DATA\WATERHTR\whtsd\Appd_B.wpd B-6

EE-RM-97-900 COMMENT 38TT
Table 1 WHAM Sample Calculation with Specified Inputs

WHAMSanme Calculation

Ipus:

10 CRpo t 430 TesmgP IwedRaads

UA 3.319(1.751) Blahr-&egF(W/degQ SlaxLby He Ls Coefficiet

RE 0.98 [-] Rc y Efficiency

Pbn 15,354(4500) Btuhr(W) Raed ltpt o

Total Voduma ofrPe Rumed

Vl 55(208) gl/day(/day) DIiig te24hrTest

bmak 140(60) degF(deg) Tlmmostat Set Rint

Tn 56(13) degF(degC) InletaWTaerT

Tanb 65(18) degF(degC) Arriae Tmwatre

ftad Chmceis csf Wter F

des 8.293752(995.25) Wb/galW(kgcubic mer) Dity ofthe Waer

M 4562(206.9) Ib(kg) Ns ofVtr Wdirtn Ding tTe 24 hr Test

Qp 1.000743(4.187) Btu/lxfegF(k/(g-degC SpecificI at of W

Results:

Qin 44468(13033) Btu/day(Wday) AvSrge Dily ey Inp

vol dens Cp (Ttank Tin) [ UADOE(Ttnk- Tamb)

Qm- -- 1-------DOE + 24 UADOE,(Ttank- Tamb)

:\DAT ER TR\whtsd OC E OEA\WA 

C :\DATA\WATERHTR\whtsd\Appd_B.wpd B-7

EE-RM-97-900 COMMENT 38TT
Table 2 UA Sample Calculation with Specified Inputs

Standby Heat Loss Coefficent (UA)

Sample Calculation

Inputs:

10 CFR part 430 Testing Procedure Results

EF 0.700 Energy Factor

RE 0.78 Recovery Efficiency

Pon 40000 (11.72) Btu/hr (kW) Rated Input Power

Operating Conditions

Removed During the 24 hr

vol 64.3 (243) gal/day (Lday) Test

Ttank 135 (57) deg F (deg C) Thermostat Set Point

Tin 58 (14.5) deg F (deg C) Inlet Water Temperature

Energy Content of Water

Withdrawn During 24 hr

Qout =M*Cp*(Ttank-Tin) Btu/day (W-h/day) Test

Physical Characteristiscs of the Water at mean of Tin & Tout at test conditions

dens 8.2938 (995.25) Ib/gal (kg/cubic meter) Density of the Water

Mass of Water Withdrawn

M 456.2 (206.9) lb (kg) During the 24 hr Test

Cp 1.0007 (4.187) Btu/lb-deg F (kJ/kg - K: Specific Heat of Water

Results:

Standby Heat Loss Coefficient

UA 3.655 (1.928) Btu/hr-deg F (W/deg C)

where,

1 1

UA= EF RE BTU

67.5- ( 24 _ 1 deg-hr 2(Qou-t -RE Ponjd

C :\DATA\WATERHTR\whtsd\Appd_B.wpd B-8

EE-RM-97-900 COMMENT 38TT
APPENDIX C: VENTING ISSUES IN GAS-FIRED WATER HEATERS

This Appendix summarizes the available data on the impacts of high-efficiency water

heaters on water heater vent system corrosion.

Introduction

Use of high flue-loss efficiency gas-fired water heaters (flue-loss efficiency generally

greater than 80.0%) with existing venting systems that are not designed for lower temperature

flue gases can potentially lead to excessive corrosion and failure of the vent system in certain

situations. DOE has recognized this potential problem and will incorporate into the efficiency

standards analysis necessary costs for venting modifications in the total installation costs for gasfired water heaters.

Venting problems are not unique to gas-fired water heaters; other gas-fired appliances

have similar problems. The gas industry, through research sponsored by the Gas Research

Institute (GRI), has identified and established new venting guidelines for high efficiency gas

furnaces'. Although there are no such guidelines for gas-fired water heaters, a few research

studies were conducted by the gas industry to evaluate the upper limits of flue-loss efficiency.

This appendix summarizes the findings of the previous studies on the impacts of highefficiency water heaters on vent system corrosion. The results from two surveys conducted by

PNNL to estimate the cost of relining exterior masonry chimneys with corrosion-resistant

material and the cost of replacing a single-wall vent connector with a double-wall vent connector

are summarised.

Background Information

Relationship between Flue-Loss Efficiency and Recovery Efficiency

Flue-loss efficiency (also referred to as thermal efficiency in the older literature; the

proposed ASHRAE Standard 90.1-1989R correctly uses thermal efficiency to refer to recovery

efficiency) is defined as the ratio of the input energy minus the energy lost through the flue in the

exhausted combustion products to the input energy.

The recovery efficiency is the percentage of energy transferred to the hot water compared

to the input energy. It takes into account the amount of the energy that is lost out of the flue and

other parts of the water heater, such as jacket and fitting losses. Therefore, recovery efficiency is

always less than the flue-loss efficiency for a given water heater.

Flue-loss efficiency is the key parameter used to estimate the amount of condensation that

can occur in a vent system because higher flue-loss efficiencies mean lower flue gas

c-i

EE-RM-97-900 COMMENT 38TT
temperatures. The DOE test procedure for rating residential-sized water heaters does not

measure this key parameter, it instead measures the recovery efficiency. Therefore, a relationship

between the flue-loss efficiency and recovery efficiency is needed to estimate the flue-loss

efficiency from the DOE test procedure results. In the past, the water heater industry suggested

that most water heaters have a recovery efficiency that is about 3% less than the flue-loss

efficiency2 The same study also noted that this number is a guideline and individual appliance

efficiencies can vary widely. The TANK water heater simulation program developed by GRI to

evaluate the design options for gas-fired storage water heaters also predicts the difference

between the two efficiencies to be at or less than 3%.3

Although the gas industry has been using the 3% difference as a rule-of-thumb for a long

time (at least since 1990), in the past year the gas industry October 23, 1998 informed DOE that

the difference between the two efficiencies may be greater than 3%.4 The basis of this claim is

six tests of water heaters that GRI recently reviewed that showed the difference between the two

efficiencies to be between 3% and 6%. In these six tests, the flue-loss efficiency was measured

in the laboratory and the recovery efficiency was inferred from the GAMA catalog for the models

tested. When DOE requested the test data for review, GAMA denied the request, stating that the

tests were incomplete and, therefore, inconclusive. The gas industry has recommended

additional tests to verify the new data.

DOE has noted these concerns and will monitor them as part of the ongoing rulemaking

process. However, because of a lack of sufficient data that conclusively shows the difference to

be higher than 3%, DOE has decided, for now, to rely on the TANK predictions and the industryestablished guideline.

Categorization of Gas Appliances

Although not formally adopted for water heaters, the gas industry uses the same gas appliance

venting system categories developed for gas furnaces. This categorization helps installers to

match the proper vent system with the appliance (Paul 1991).

A Category I appliance is defined as an appliance that has a flue-loss efficiency of less

than 83%, and operates under negative pressure in the vent. Most water heaters sold today are

classified as Category I appliances. 5 Most Category I appliances rely on the natural draft of the

hot combustion products for venting, however some rely on fans or blowers to push or pull the

combustion products through the appliance to overcome the flow resistance (with the vent still

under negative pressure).

Appliances that have a flue-loss efficiency of greater than 83% and operate under

negative pressure are classified as Category II appliances. Category III appliances have flue-loss

efficiencies of less than 83% but operate under positive pressure in the vent system. Similarly,

Category IV appliances operate under positive pressure but have flue-loss efficiencies greater

than 83%.

C-2

EE-RM-97-900 COMMENT 38TT
All Category II, III, and IV appliances have special venting requirements that are

specified by the manufacturers. These units, in general, cannot be vented into existing vent

systems without major modifications. The modifications for Category II units include a

condensate drain and corrosion-resistant vent material (usually PVC, because the vent

temperatures are low). Category III units are permitted to vent side-ways, but need pressure-tight

vent systems. Category IV units require a condensate drain, corrosion-resistant vent material,

and pressure-tight vents.

Most gas-fired water heaters sold today are classified as Category I appliances because

the flue-loss efficiency for those units is less than 83% and they operate under negative pressure

in the vent system. The maximum flue-loss efficiency corresponding to the proposed design

options being considered is less than 83%, and will not require forced venting; therefore,

Category I water heaters will still dominate the market even if the option with the maximum

proposed flue-loss efficiency is accepted as the new manufacturing standard for residential-sized

water heaters.

Summary of Previous Studies

This section summarizes the previous studies by the gas industry that deal with specific

issues related to masonry chimneys, vent connectors, and various scenarios of installation of high

flue-loss efficiency (>80.0%) water heaters and modifications that may be required to avoid

excessive wet-times in the vent systems.

Masonry chimneys have to be wet for a significant period of time (over 1000 hours) for

any damage to occur. 6 GRI estimated that 53% of U.S. residences have common vent systems

for water heaters and furnaces. With increased minimum furnace efficiency requirements (since

1992), most replacement furnaces now have higher efficiencies than the units they are replacing.

Although masonry chimneys are quite resilient to corrosion, relining may be necessary in some

cases when the existing low flue-loss efficiency furnace is replaced with a high flue-loss

efficiency furnace. Because furnace on-times are significantly higher than water heater on-times,

masonry chimneys rely on the furnace to dry the condensate deposited by the water heater. In

high flue-loss efficiency furnaces, the flue gas temperatures are lower, thereby increasing the

potential of excessive wet-times in the chimney.

The various situations arising from the replacement of gas-fired water heaters and

furnaces are discussed in the following sections.

Replacement Installations

Most water heaters sold today are for the replacement market. Therefore, in some cases,

replacement of a low flue-loss efficiency (< 80%) water heater with a high flue-loss efficiency

water heater (> 80%) into an unmodified existing vent system may lead to excessive wet-times

and thereby corrode the vent system. In almost all replacement situations, there are vent systems

and reliners on the market to meet the venting requirements for installing high flue-loss

C-3

EE-RM-97-900 COMMENT 38TT
efficiency water heaters - there are no technological barriers to using high flue-loss efficiency

water heaters in a replacement situation.

Base Case-Two-Appliance Configuration

In the following section, a base case installation for a two-appliance configuration is

defined and the effect on the vent system when the base case unit is replaced with a high flue-loss

efficiency unit with varying characteristics and under various conditions is discussed. All the

information is extracted from the GRI, 1991 report and the findings are summarized in Table

C.2.

A base case configuration is assumed to have two natural draft appliances, a furnace and a water

heater venting into a common vent system. The flue-loss efficiency of each of these units is

assumed to be less than 80%. The vent connectors are assumed to be single wall metallic

connectors and the vent to be an exterior masonry chimney that is properly sized.

Replace Existing Water Heater with a Water Heater Equipped with Draft Hood and a FlueLoss Efficiency of 80.0%

Since the water heater is equipped with a draft hood and also because the flue-loss

efficiency is not greater than 80.0%, the new water heater can continue to vent into the existing

vent system.

Replace Existing Water Heater with a High Flue-Loss Efficiency Model

If the flue-loss efficiency of the water heater exceeds 83%, the exterior masonry chimney

needs relining in all DOE defined regions of the United States. DOE regions are listed in Table

C.1. If the flue-loss efficiency of the replacement unit exceeds 80.0% but is less than 83%,

relining may be necessary only in some regions.

Table C.1 DOE Regions

Climate Zone Location Cooling Degree Heating Degree

Days Days

Region I Minneapolis, MN 750 8070

Region II Chicago, IL 998 6194

Region III Washington, D.C. 1425 4236

Region IV Pasadena, CA 1053 1670

Region V Charleston. NC 2047 2193

C-4

EE-RM-97-900 COMMENT 38TT
Replace Existing Furnace with a High Flue-Loss Efficiency Fan-Assisted Model

When the new high flue-loss efficiency (83%) furnace (fan-assisted combustion) vents

into the existing chimney, relining the chimney is recommended in all DOE regions, except for

DOE region I (Phillips 1994). If the flue-loss efficiency of the furnace is 80.0%, then relining is

required in regions II and IV under some circumstances but is always required in DOE region V.

Replace Both Existing Water Heater and Furnace with a High Flue-Loss Efficiency Models

The exterior masonry chimney has to be relined in all DOE regions if the flue-loss

efficiency of either of the two appliances exceeds 83%, and in some regions if the flue-loss

efficiency exceeds 80.0% (but is less than 83%).

A Case of an "Orphaned" water heater

When an existing commonly vented furnace is replaced with a high flue-loss efficiency

furnace requiring its own vent system, it "orphans" the water heater (i.e., the water heater is left

alone to vent into the exterior masonry chimney). Depending on the region and the efficiency of

the water heater, the existing chimney may have to be relined.

Table C.2 Summary of Recommendations for Relining Exterior Masonry Chimneys for

Residential Installations in a Two-Appliance Configuration

Option Comment

Base case: both furnace and water heater w/

flue-loss efficiency less than 80% No relining is necessary

Replace base case water heater with 80.0%

efficient (flue-loss) unit No relining is necessary

Replace base case water heater with 83% Relining may be needed in most DOE

efficient (flue-loss) unit regions

Replace base case furnace with 83% Relining of the chimney is recommended in

efficient (flue-loss) unit (fan-assisted) all regions except DOE region I

If the flue-loss efficiency is between 80.0%

and 83%, chimneys in some DOE regions

Replace base case water heater and furnace may need relining. If the flue-loss efficiency

with high flue-loss efficient units is above 83%, relining is recommended in

all regions except region I.

"Orphaned" water heater Relining is recommended in all DOE

regions

C-5

EE-RM-97-900 COMMENT 38TT
Base Case - One-Appliance Configuration

In the following section, a base case installation with only a water heater venting into a

vent system is defined, and the effect on the vent system when the base case unit is replaced with

a high flue-loss efficiency unit with various characteristics is discussed. At the end of the

section, the findings are summarized in Table C.3.

A base case configuration is assumed to have a natural draft water heater venting into a

exterior masonry chimney. The flue-loss efficiency of the unit is assumed to be less than 80%.

The vent connectors are assumed to be single wall metallic connectors and the vent is assumed to

be properly sized.

Replace Existing Water Heater with a Water Heater Equipped with Draft Hood and a FlueLoss Efficiency of 80.0%

Since the water heater is equipped with a draft hood and also because the flue-loss

efficiency is not greater than 80.0%, the new water heater can continue to vent into the existing

vent system.

Replace Existing Water Heater with a High Flue-Loss Efficiency Model

If the flue-loss efficiency of the water heater exceeds 83%, the exterior masonry chimney

needs relining in all DOE regions. If the flue-loss efficiency of the replacement unit exceeds

80.0% but is less than 83%, relining may be necessary in most regions, except for DOE region I.

Table C.3 - Summary of General Recommendations for Relining Exterior Masonry Chimneys for

Residential Installations in a One-Appliance Configuration

Option Comment

Base case: flue-loss efficiency of the water

heater is less than 80% No relining is necessary

Replace base case water heater with 80.0%

efficient (flue-loss) unit No relining is necessary

Replace base case water heater with 83% Relining may be needed in most DOE

efficient (flue-loss) unit regions, except DOE region I

New Construction

Most water heaters with efficiencies greater than 80.0% require manufacturer-specified

vent systems. Therefore, in new construction with a proper vent system, there is no upper limit

on the flue-loss efficiency. Some issues related to new construction installations are:

Use of high flue-loss efficiency (greater than 80.0%) water heaters do not constitute venting

C:\DATA\WATERHTR\whtsd\Appd_C.wpd C-6

EE-RM-97-900 COMMENT 38TT
problems, because there are vent systems currently on the market that will handle low

temperature flue gases and any potential corrosion from the condensate.

*There are no general guidelines similar to the National Fuel Gas Code (NFGC) for Category I

appliances for installing vents for high flue-loss efficiency water heaters.

Manufacturers of high flue-loss efficiency water heaters are required to provide the vent

installation instructions.

Installers are generally not aware of potential venting problems and availability of alternate

vent systems.

If proper venting systems are used and installed according to manufacturers'

recommendations, there is no upper limit for flue-loss efficiency.

Vent Connectors

The portion of the vent system connecting the gas appliance flue collar or draft hood to

the vent is called a vent connector. A single wall vent connector limits the flue-loss efficiency of

gas appliances to 80.0% in a worst case installation (Talbert, 1995).

According to GRI, use of single-wall vent connectors is restricted to appliances with flue-loss

efficiency of up to 80.0%, because efficiencies above 80.0% increase the wet-times in the

connectors significantly.

Higher flue-loss efficiency units can be allowed if the draft-hood diameters are increased

slightly, for example, from 3" to 4".

Use of Type-B metal vent connectors with Type-B metal vents will allow for higher

minimum flue-loss efficiency (up to 84% from 80%). If a water heater has a flue-loss

efficiency of 84% or higher, a condensate drain may also be needed.

Type-B metal vent connectors and Type-B metal vents are also recommended for water

heaters installed in unheated spaces (such as in a garage, basements, outdoors).

GRI estimates an upper limit of 83.5% to 84% flue-loss efficiency in a typical house. (A

typical installation uses a single wall metal vent connector and a Type-B metal vent and has a

capacity of 35,000 Btu/hr. A worst case installation has a flue-loss efficiency upper limit of

80.0%).

C :\DATA\WATERHTR\whtsd\Appd C.wpd C-7

EE-RM-97-900 COMMENT 38TT
Vent Modification Cost Summary

Since there are a significant number of masonry venting system in the U.S., DOE recognizes

that there could be a potential problem if energy efficiency standards resulted in gas-fired water

heaters with high flue-loss efficiencies (>80.0%). Therefore, DOE will incorporate into the

analysis for standards, where necessary, the costs of venting modifications in water heater

installation costs. Relining the vent system and installation of double -wall vent connectors may

be necessary when some existing gas appliances (water heaters and furnaces) attached to exterior

masonry chimneys are retrofitted with higher flue-loss efficiency units (flue-loss efficiency

greater than 83%).

In this section, the cost estimates obtained by DOE for relining exterior masonry chimneys

are presented and compared with the costs published in the 1991 GRI report. The primary reason

for the comparison is to verify that the costs reported in the 1991 report are still valid (after

adjusting for inflation).

Two consultants to PNNL (one from Portland, OR and the other from Grand Rapids, MI)

collected two separate sets of data (herein called Data Set 1 and Data Set 2) to estimate the cost

of relining the vent system and the cost of Type-B vent connectors.

Data Set 1 Results. The Portland contractor conducted a quick nationwide survey of chimney

sweeps who actively reline chimneys for gas appliances. All of these sweeps operate successful

and relatively large businesses; several of them serve on the Board of Directors of the National

Chimney Sweep Guild. Nine responses to the request for information were received - seven from

the East, one from the Midwest, and one from the West.

The sweeps were asked to provide materials and labor cost for relining exterior masonry

chimneys with the three most commonly used relining materials: Aluminum (flexible), Type-B

metallic, and AL29-4C Stainless Steel. They were asked to provide separate estimates for oneand two-story houses having either a 4" or a 5" diameter chimney flue. The height of the flue was

not specified: the respondents were allowed to use their judgment for what is typical in their

region for one- or two-story detached houses.

The average costs of relining the exterior masonry chimneys are summarized in Table C.4.

The left-hand side of the table provides average costs from all nine responses and the right-hand

side of the table provides average costs with the highest and lowest estimates (outliers) dropped.

The bottom line shows the cost estimates from the 1991 GRI report (converted $1998) for the

same relining materials.

C:\DATA\WATERHTR\whtsd\Appd_C.wpd C-8

EE-RM-97-900 COMMENT 38TT
Table C.4 Data Set 1 - Summary of Cost Estimates and Comparison with the GRI

Vent Diameter/ Average with Outliers

No. of Stories Average of All Responses Dropped

Aluminum Type-B AL29-4C Aluminum Type-B AL29-4C

4"/one $689 $757 $1,040 $479 $603 $893

5"/one $769 $840 $1,174 $558 $711 $1,049

4"/two $833 $940 $1,288 $602 $788 $1,146

5"/two $912 $1,021 $1,434 $679 $888 $1,305

GRI Reported Cost Estimates $505 $505 $1,285

The GRI cost estimates are based on a baseline vent system with a single wall vent

connector (4" in diameter, 8' long with two elbows) attached to either a Type-B vertical vent (5"

in diameter, 22' high) or a masonry chimney (also 22' high from the breaching to the top of the

chimney outlet). The relining cost estimates from Data Set 1 are generally higher than those

reported in the GRI report. The discrepancy may be due to the fact that the flue height was not

specified in the sweeps' survey and the respondents may have assumed a worst case scenario.

The complete data are presented at the end of this appendix in Table C.6 (responses I thru IX).

Data Set 2 Results. The Grand Rapids consultant was asked was asked to estimate the

cost for a baseline vent system as specified by the GRI document. The consultant interviewed

six installers in Grand Rapids, MI. None of the interviewees had experience with installing

Type-B or AL29-4C reliners, and therefore, only provided cost estimates for relining the vent

systems with aluminum. The value of $309 represents the average from all six responses and

includes materials and labor. This group also provided a cost estimate for replacing single-wall

vent connector with Type-B vent connector. Table C.5 summarizes the costs collected from Data

Set 2. The raw data is shown in Table C.6 (responses X thru XV).

Table C.5 Data Set 2 - Summary of Cost Estimates

Aluminum Type B Vent Connector

8" Length Elbow (each) Labor

$309

$52 $31 $36

Data Collection Conclusion. The average cost to reline the vent system in a one-story

house with a 5" diameter chimney flue with aluminum for both Data Sets 1 & 2 is approximately

$433. This compares with $505 ($1998) in the GRI estimates.

The GRI cost estimate for replacing a single-wall vent connector with a Type-B double

wall vent connector was $105 ($1998) compared to the survey estimate of $114 (8" length. 2

C:\DATA\WATERHTR\whtsd\Appd_C.wpd C-9

EE-RM-97-900 COMMENT 38TT
elbows). DOE has decided to use the estimates from the recent two data sets for replacing a

single-wall vent connector with a Type-B double wall vent connector. The Department has not

considered design options that would require chimney reining.

C:\DATA\WATERHTR\whtsd\AppdC.wpd C-10

EE-RM-97-900 COMMENT 38TT
Table C.6

Raw Survey Data

One-Story Two-Story

4" 5" 4" 5"

Materials Labor Total Materials Labor Total Materials Labor Total Materials Labor Total

Response I Aluminum $201.00 $345.00 $546.00 $283.00 $414.00 $697.00 $300.00 $525.00 $825.00 $378.00 $525.00 $903.00

AL29-4C $731.00 $345.00 $1,076.00 $831.00 $414.00 $1,245.00 $1,104.00 $525.00 $1,629.00 $1,240.00 $525.00 $1,765.00

Type B $221.00 $345.00 $566.00 $278.00 $414.00 $692.00 $318.00 $525.00 $843.00 $411.00 $525.00 $936.00

Response II Aluminum $213.20 $581.80 $795.00 $245.25 $604.75 $850.00 $213.20 $581.80 $795.00 $245.25 $604.75 $850.00

AL29-4C $751.85 $546.15 $1,298.00 $846.25 $551.75 $1,398.00 $842.11 $555.89 $1,398.00 $949.43 $548.57 $1,498.00

Type B $197.42 $600.00 $797.42 $223.32 $600.00 $823.32 $226.20 $600.00 $826.20 $256.56 $600.00 $856.56

Response Ill Aluminum

AL29-4C $245.00 $225.00 $470.00 $285.00 $225.00 $510.00 $435.00 $350.00 $785.00 $443.00 $390.00 $833.00

Type B $90.00 $175.00 $265.00 $110.00 $180.00 $290.00 $146.00 $250.00 $396.00 $170.00 $275.00 $445.00

Response IV Aluminum $146.00 $300.00 $446.00 $161.00 $300.00 $461.00 $176.00 $400.00 $576.00 $198.00 $400.00 $598.00

AL29-4C $491.00 $450.00 $941.00 $539.00 $450.00 $989.00 $680.00 $450.00 $1,130.00 $755.00 $450.00 $1,205.00

Type B

Response V Aluminum $351.72 $1,600.00 $1,951.72 $4.6 1,600.00 2,034.64 $387.40 ,600.00 $1,987.40 $477.06 $1,600.00 $2,077.06

AL29-4C $876.72 $1,600.00 $2,476.72 $950.94 $1,600.00 $2,550.94 $1,246.86 $1,600.00 $2,846.86 $1,364.20 $1,600.00 $2,964.20

Type B $264.84 $1,600.00 $1,864.84 $307.46 $1,600.00 $1,907.46 $337.60 $1,600.00 $1,937.60 $394.06 $1,600.00 $1,994.06

(C:\I)AITA\WA'TIIRlI ITR\whlsd\AppdC.wpd C-l C-I I

EE-RM-97-900 COMMENT 38TT
Response VI Aluminum

AL294C

Type B $104.44 $55.00 $159.44 $180.00 $80.00 $260.00 $260.00 $125.00

Response Vll Aluminum $150.00 $160.00 $310.00 $170.00 $175.00 $345.00

AL294C $325.00 $160.00 $485.00 $370.00 $175.00 $545.00 $410.00 $170.00 $580.00 $490.00 $190.00

Type B $300.00 $160.00 $460.00 $370.00 $200.00 $570.00

Response VIII Aluminum $248.31 $150.00 $398.31 $328.70 $200.00 $528.70 $283.00 $150.00 $433.00 $380.00 $200.00

AL294C $661.85 $225.00 $886.85 $772.00 $300.00 $1,072.00 $826.44 $225.00 $1,051.44 $932.00 $300.00

Type B $315.00 $275.00 $590.00 $460.00 $300.00 $760.00 $420.00 $275.00 $695.00 $572.00 $300.00

Response IX Aluminum $228.92 $150.00 $378.92 $264.16 $200.00 $464.16 $228.92 $150.00 $378.92 $264.16 $200.00

AL294C $423.85 $260.00 $683.85 $839.11 $240.00 $1,079.11 $623.31 $260.00 $883.31 $1,037.03 $260.00

Type B

Response X Aluminum $150.00. $225.00 $375.00

Response XI Aluminum $200.00 $125.00 $325.00

Response XII Aluminum $225.00 $125.00 $350.00

Response Xlll Aluminum $200.00 $100.00 $300.00

Response XIV Aluminum $210.00 $90.00 $300.00

Response XV Aluminum $125.00 $80.00 $205.00

C':\l)A IA\WA'I'RI If R\whtsd\Appd_C.wpd C-12

EE-RM-97-900 COMMENT 38TT
References

1. GAMA. 1990. Venting Tables for Category I Central Furnaces ", Supplementary

Installation Instructions Distributed with Furnaces Shipped Since September 1990,

Arlington, VA.

2. Paul, D.D. W.J. Sheppard, G.R. Whitacre, R.D. Fischer, A.L. Rutz, D.W. Locklin, J.J

Crisafulli, G.H. Stickford, A.L. Murray, D.K. Landstrom, S.G. Talbert, A.R. Buhr, D.W.

DeWerth, C.A. Farnsworth, R.L. Loria, and J.A. Pietsch. 1991. Assessment of Technology

for Improving the Efficiency of Residential Gas-fired Water Heaters. GRI-91/0298, Gas

Appliance Technology Center, Gas Research Institute, Chicago, IL.

3. Paul, D.D, G.R. Whitacre, R. D. Fischer, J. J. Crisafulli, A. L. Rutz, J. G. Murray, and G.

S. Holdebaum. 1993. TANK Computer Program and User's Manual with Diskettes.

GRI-93/0186, Gas Appliance Technology Center, Gas Research Institute, Chicago, IL.

4. Conference calls, GAMA and DOE, March 1998 and July 1998,

5. Talbert S.G., D.B. Philips, G.R. Whitacre, J.J. Crisafulli, and A.L. Rutz. 1995.

"Categorization of Criteria for Residential Draft-Hood-Equipped Gas Water Heaters."

GRI-95/0198, Gas Appliance Technology Center, Gas Research Institute, Chicago, IL.

6. Phillips D.B, A.L. Rutz, G.R. Whitacre, S.G. Talbert. 1994. Venting Gas Appliances into

Exterior Masonry Chimneys: Analysis and Recommendations. GRI-94/0193, Gas

Appliance Technology Center, Gas Research Institute, Chicago, IL.

C:\DATA\WATERHTR\whtsd\Appd_C.wpd C-13

EE-RM-97-900 COMMENT 38TT
APPENDIX D: MANUFACTURER COST DATA FOR RESIDENTIAL

ELECTRIC AND GAS-FIRED WATER HEATERS

This Appendix presents the manufacturer cost data for residential electric and gas-fired

water heaters provided to the U.S. Department of Energy by the Gas Appliance Manufacturer

Association Inc. (GAMA), on July 17, 1998, for use in the rulemaking process to amend the

federal efficiency standards for such products.

Introduction

The cost data supplied by GAMA are a primary input to the Engineering and the LifeCycle Cost analyses. GAMA collected cost data directly from the major manufacturers of

electric and gas-fired water heaters. No data was supplied for oil-fired or LPG water heaters,

which are also covered in this analysis. The GAMA data consisted of estimates of the

manufacturer cost for a defined baseline model and for design options to increase the efficiency

of this model. Before providing the data to DOE, it was aggregated to protect the confidentiality

of the individual manufacturers submissions. Note that data were provided for typical 50-gallon

electric and 40-gallon gas-fired water heaters only.

Data Format

The cost data were provided in a format developed by the Arthur D. Little Company to

reflect the order of the design options used in the analysis. GAMA used the term "level" to

indicate the ordering sequence of the design options. The following table shows the GAMA

"levels" as they were provided with the data.

GAMA Electric Water Heaters Gas-fired Water Heaters

Level

I Baseline Baseline

2 Heat Traps Heat Traps

3 2" Improved Insulation 2" Improved Insulation

4 2.5" Improved Insulation* Flue Damper (electro-mechanical)

5 Plastic Tank* Improved Flue Baffle

6 Insulated Bottom Tank Electric Ignition (IID)

7 Side Arm Heater*

8 _Improved Combustion Chamber

*Because of insufficient data, GAMA did not provide data for three of the design options being considered: 2.5"

improved insulation, plastic tank, and side arm heater.

For the baseline unit and the design options, separate data were provided for variable

manufacturing cost, fixed manufacturing cost, and the total manufacturing cost. The variable

cost represents materials, labor, overhead, and transportation; fixed cost is the capital and product

design cost on a per unit basis; and the total cost is the sum of the variable and the fixed

manufacturing cost.

D-l

EE-RM-97-900 COMMENT 38TT
The GAMA data are presented in Tables D. 1 through D.6. For example in terms of

cumulative frequencies distribution functions for each design option cost. Each table contains a

set of cost values below which a given percentage of manufacturers said that they could produce

a given technology option. The tables were generated by sampling from the aggregate

distributions of manufacturing cost provided to GAMA by the water heater manufacturers. The

values are the result of 10,000 random samples from these aggregate distributions.

Table D. 1 - Electric Water Heaters Cumulative Variable Cost

Table D.2 - Electric Water Heaters Cumulative Fixed Cost

Table D.3 - Electric Water Heaters Cumulative Total Cost

Table D.4 - Gas-fired Water Heaters Cumulative Variable Cost

Table D.5 - Gas-fired Water Heaters Cumulative Fixed Cost

Table D.6 - Gas-fired Water Heaters Cumulative Total Cost

In addition GAMA provided average values for the design option components of the variable and

the fixed costs. This data are shown in Table D.7 and D.8.

D-2

EE-RM-97-900 COMMENT 38TT
GAMA Manufacturing Cost - Electric Water Heaters (50-gal)

Table D.1 Cumulative Variable Cost

Lvl Design Options Variable Costs

Percentiles

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1 Baseline 84.96 93.00 97.74 98.38 98.38 101.54 139.21 145.80 154.46 159.70 171.82

2 HeatTraps 105.02 105.02 105.02 110.91 110.91 110.91 140.58 147.43 156.85 162.31 174.54

3 2" Improved Insulation 93.34 102.26 107.01 130.15 133.71 140.63 155.11 158.92 161.92 165.93 175.97

4 2.5" Improved Insulation 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5 Plastic Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8 Insulated BottomTank 131.88 134.81 136.53 138.61 141.31 146.40 162.57 165.34 168.11 171.88 181.08

GAMA Manufacturing Cost - Electric Water Heaters (50-gal)

Table D. 2 Cumulative Fixed Cost

Lvl Design Options Fixed Cost

Percentiles

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1 Baseline 0.99 0.99 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.01 1.01

2 Heat Traps 0.12 0.12 0.12 0.23 0.24 0.27 0.47 0.50 0.68 0.72 0.78

3 2" Improved Insulation 0.39 0.47 0.52 0.62 0.65 0.72 2.39 2.42 19.28 20.28 22.01

4 2.5" Improved Insulation 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5 Plastic Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8 Insulated Bottom Tank 2.53 2.66 2.73 2.81 2.92 3.12 3.90 3.95 4.01 4.09 4.27

D-3

EE-RM-97-900 COMMENT 38TT
GAMA Manufacturing Cost - Electric Water Heaters (50-gal)

Table D.3 Cumulative Total Cost

Lvl Design Options Total Cost

Percentiles

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1 Baseline 85.96 93.99 98.74 99.38 99.38 102.54 140.21 146.81 155.47 160.70 172.82

2 Heat Traps 105.45 105.49 105.52 111.14 111.15 111.18 141.30 148.12 157.01 162.43 174.66

3 2" Improved Insulation 93.80 102.73 107.50 130.80 134.36 141.33 162.99 168.27 173.58 179.74 194.83

4 2.5" Improved Insulation 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

5 Plastic Tank 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8 Insulated Bottom Tank 134.62 137.61 139.33 141.41 144.13 149.16 166.57 169.36 172.10 175.89 185.22

GAMA Manufacturing Cost - Gas-fired Water Heaters (40-gal)

Table D.4 Cumulative Variable Cost

Lvl Design Options Variable Costs

Percentiles

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1 Baseline 104.31 114.33 119.90 129.57 133.05 137.49 144.18 149.55 154.93 160.83 174.40

2 HeatTraps 107.84 118.37 124.01 133.12 136.47 140.78 145.99 151.80 157.69 163.63 178.26

3 2" Improved Insulation 111.68 122.16 128.09 150.61 153.42 156.10 158.96 162.44 166.92 173.07 187.92

4 Flue Damper (electro-mechanical) 193.55 200.11 206.99 225.16 234.01 239.94 246.05 254.29 293.25 307.78 334.75

5 Improved Flue Baffle 112.42 123.03 128.70 131.41 134.38 140.15 148.66 154.89 161.49 168.76 183.51

6 Electric Ignition (lID) 138.48 152.27 159.29 169.62 174.30 182.94 199.36 209.02 242.97 254.90 276.93

7 Side Arm Heater 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8 Improved Combustion Chamber 172.07 196.94 206.17 212.02 217.39 224.26 238.52 278.89 284.10 290.94 307.51

D-4

EE-RM-97-900 COMMENT 38TT
GAMA Manufacturing Cost - Gas-fired Water Heaters (40-gal)

Table D.5 Cumulative Fixed Cost

Lvl Design Options Fixed Cost

Percentiles

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1 Baseline 0.99 0.99 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.01 1.01

2 Heat Traps 0.01 0.01 0.01 0.12 0.13 0.14 0.28 0.29 0.36 0.38 0.42

3 2" Improved Insulation 0.01 0.01 0.01 0.26 0.29 0.32 0.34 0.36 4.99 5.23 5.69

4 Flue Damper (electro-mechanical) 0.19 0.20 0.22 0.51 0.54 0.60 5.53 5.80 15.05 15.78 17.13

5 Improved Flue Baffle 0.14 0.21 0.22 0.24 0.29 0.39 0.95 1.01 9.70 10.19 11.07

6 Electric Ignition (IID) 0.12 0.13 0.14 0.16 0.16 0.76 0.81 0.87 12.60 13.25 14.39

7 Side Arm Heater 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8 Improved Combustion Chamber 1.40 1.49 1.56 1.66 2.04 2.12 2.20 3.51 4.63 5.43 7.23

GAMA Manufacturing Cost - Gas-fired Water Heaters (40-gal)

Table D.6 Cumulative Total Cost

Lvl Design Options Total Cost

Percentiles

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1 Baseline 105.32 115.33 120.90 130.57 134.05 138.49 145.18 150.55 155.94 161.83 175.40

2 Heat Traps 108.12 118.66 124.28 133.24 136.64 141.02 146.35 152.07 157.88 163.64 178.27

3 2" Improved Insulation 111.94 122.45 128.38 151.88 154.98 158.31 161.60 164.88 169.05 174.04 187.93

4 Flue Damper (electro-mechanical) 193.75 200.31 207.21 226.40 235.95 242.96 250.03 259.04 308.84 323.53 351.40

5 Improved Flue Baffle 112.75 123.29 128.95 131.65 134.64 141.42 157.51 161.92 166.12 170.84 184.47

6 Electric Ignition (IID) 138.64 152.43 159.45 170.45 175.12 183.71 199.49 209.15 255.95 267.98 289.85

7 Side Arm Heater 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

8 Improved Combustion Chamber 175.88 200.84 209.09 214.97 220.13 227.41 243.38 280.49 285.66 292.51 309.12

D-5

EE-RM-97-900 COMMENT 38TT
Table D.7 Average Design Option Component Costs - Electric Water Heaters

Variable Costs Fixed Costs

Material Labor Transportation Overhead Total Capital Product

Design

DOE Design Options $/Unit $/Unit $/Unit $/Unit $/Unit $mln $ min

I Baseline 62.16 12.41 10.11 40.88 125.56 --

2 Heat Traps 64.75 12.61 10.11 41.71 129.18

3 2" Improved Insulation 70.39 12.92 11.55 43.1 137.96

4 2.5" Improved Insulation -- -- -- --

5 Plastic Tank

6 Insulated Tank Bottom -- -- -- -- --

Table D.8 Average Design Option Component Costs - Gas-fired Water Heaters

Variable Costs Fixed Costs

Material Labor Transportation Overhead Total Capital Product

Design

DOE Design Options $/Unit $/Unit $/Unit $/Unit $/Unit $mln $ min

1 Baseline 75.02 12.49 9.67 40.43 137.61 -- --

2 Heat Traps 77.77 12.65 9.67 40.64 140.73 0.07 0.13

3 2" Improved Insulation 83.53 13.09 12.23 42.8 151.65 0.85 0.59

4 2.5" Improved Insulation -- -- -- -- -- -- --

5 Plastic Tank -- -- -- -- --

6 Improved Flue Baffle 75.99 13.78 9.67 41.75 141.19 1.17 1.72

7 Multiple Flues -- -- -- -- --

8 Improved Combustion Chamber 134.24 21.68 10.82 62.03 228.77 1.42 1.4

9 Submerged Combustion Chamber -- -- -- -- -- -- --

10 Flue Damper (electro-mechancial) 160.07 16.61 16.84 49.13 242.65 3.45 2.03

11 Side Arm Heater -- -- --

12 Two Phase Thermosiphon -- -- . --- 

13 lID 118.8 15.77 14.51 47.31 196.39 2.09 1.47

D-6

EE-RM-97-900 COMMENT 38TT
D-7

EE-RM-97-900 COMMENT 38TT
APPENDIX E: OIL-FIRED WATER HEATERS CONDUCTIVE HEAT LOSS

CALCULATION

This Appendix presents the detailed approach taken in this analysis to calculate the heat

loss through the top and sides of oil-fired waters.

Heat Loss Calculation

Water heater jacket heat losses were calculated as conductive heat losses from the water

through the insulation to the jacket in series with convective and radiative heat transfers from the

jacket to the surrounding air and environment. Conductive heat losses are calculated using

standard conductive heat transfer equations. The equations for conductive heat transfer through

the top and sides are':

Qond top = (k * areaso /th,) * (Tank- Tjiked (1)

and

Qcondde= [(k-2-nheight) / (144- In (diamcke,/ diam,a))] (Ta -Tae,) (2)

where

k = equivalent conductivity of insulation (Btu-in/hr-ft2-0F) or (W/m2-°C),

area, = area of top of tank (ft2) or (cm2),

thnsl = thickness of insulation (in) or (cm),

height = height of tank (in) or (cm),

diamiacke, = diameter of jacket (in) or (cm),

diam,an = diameter of tank (in) or (cm),

Tank = temperature of tank (°F) or (°C),

Tjace, = temperature of jacket (°F) or (°C,),

144 = conversion factor (ft/in2) (non-SI units only),

The foam insulation is HFC-245fa, with a conductivity (k) of 0.0144 Btu/hr-ft-°F (0.0249

W/m-°C) 2.

Convective heat loss from the jacket to the surrounding air is calculated as:

Q_conv = J, hconv, .area, (Tacke, - Tm,) (3)

where

hconv, = convective heat transfer coefficient for surface i (Btu/hr-ft2-°F) or

(W/m2-°C),

area, = area of surface i of tank (ft2) or (cm 2

),

Tmb = temperature of ambient air (°F) or (°C).

E-l

EE-RM-97-900 COMMENT 38TT
The convective heat transfer coefficient varies depending on surface orientation, so the

total convective heat loss is a summation of all of the heat losses from the tank surfaces exposed

to the surroundings (the top and sides of the tank). The relationships used for the convective heat

transfer coefficients are3:

for horizontal heat flow: hconv = 0.19 (Tjacket-Tamb) 33 (Btu/h-ft2-oF)

for vertical upwards heat flow: hconv = 0.22 (TjacketTamb) 0 33 (Btu/h-ft2-oF)

or

for horizontal heat flow: hconv = 1.31 (Tjaket-Tab)0 3

3 (W/m-°C)

for vertical upwards heat flow: hconv = 1.52 (Tjack,e-Tab)0 33 (W/m-°C)

The radiative heat loss from the jacket to the surroundings was calculated as:

Qrad = , hrad area, (Tacke, - Tam (4)

where area, is define as for equation 3, and where the radiative heat transfer coefficient is

defined as:

hd = e * a * [(Tjcke + (Tamb2 ]. ( Tacke,_R + Tamb_R) (5)

where

a = the Stephan-Boltzman constant, 0.1714 * 10'8} Btu/hr-ft2-°R 4 (5.6697

x 10-8 W/m2 -K4),

E = emissivity of water heater surface, or white painted surfaces, 0.87,

Tjacke _R = the absolute temperature of the water heater jacket (°R) or (K),

Tmb R = the absolute temperature of the environment around the water heater

(°R) or (K).

Equation (5) is based on the simplifying assumption that the jacket is completely

surrounded by a black body enclosure at the ambient temperature'. Since in most cases the space

the tank is located in is significantly larger than the tank itself, this is a good working

assumption.

At steady-state conditions, the heat flow from the tank through the insulation must equal

the heat leaving the jacket by convective and radiative cooling:

Qcond = Qcn, + Qrad (6)

All three terms are dependent on the unknown jacket temperature, with the radiative and

convective heat losses non-linear with temperature. To solve equation (6), the jacket temperature

is chosen iteratively until the conductive heat loss matches the sum of the convective and

radiative losses. This jacket temperature can then be used to solve for the total conductive heat

loss from the top and sides of the tank.

E-2

EE-RM-97-900 COMMENT 38TT
Both RE and UA are changed by a reduction in total jacket heat loss, as it occurs

continuously. Since jacket losses are continuous losses, they are related to the RE through

equation (7) below.

Loss_continuous + Lossflue_on = Po, (1 - RE) (7)

Thus,

RE = 1- (Loss continuous + Lossflue_on) /Po (8)

And subtracting the RE for two different levels of jacket loss when all other losses are

held constant gives:

RE2 - RE, = (Losscontinuous, - Loss_continuous) /Pon (9)

or, since the differences in continuous losses is equivalent to the difference in jacket losses,

RE2 - RE, = (Jacket_loss, - Jacketloss) /Pon (10)

The standby heat loss rate is:

Standby heat loss rate = UA (Tank - Tam) (11)

This "standby heat loss rate" is the average rate of heat input needed to maintain a tank at

a constant temperature during standby. It includes continuous losses, flue losses when firing, and

flue losses and piping losses during the off-cycle. If an assumption is made that the time to reach

the nominal water temperature after a draw is short compared to the length of the test, an overall

balance on losses during the test period can be developed as:

UA (T,ak - Tamd(24 - BOHdr,) = (Loss_continuous + Loss_flue_off (24 - BOH,,-

BOHdaJ + BOH,,Po,,(1 - RE) (12)

where

BOHd,, = Burner operating time to make up for hot water drawn from the tank

(hr),

BOH,, = Burner operating time to make up for standby losses (hr).

BOH,, can be calculated from the total energy required during the standby period divided

by the energy input during firing. The energy required to make up for losses during the standby

period is equal to the energy input for the whole DOE test minus the energy that is actually used

to heat water removed from the tank. The procedure to develop the equation for BOH,, is:

E-3

EE-RM-97-900 COMMENT 38TT
Q.sby = Qn - Qrecov (13a)

Qin = Qdrw /EF (13b)

Qrecov = Qdr/w RE (13c)

Qs,by = BOH5, * Pon = Qdr, / EF - Qdr, / RE (13d)

and

BOHs, = /P,, Qdr w (1/EF-1/RE) (13)

Where

Qby = the input energy to make up for standby losses during the test

Qn = the input energy used during the test

Qrecov = the input energy needed to make up for the hot water drawn from the tank

Qdrw = the heat content of water drawn from the tank during the test

And by default

BOHdw = BOH-BOH,, (14)

BOH is calculated as shown in equation (A) of the oil-fired section of the report as

BOH = Qdra / (EF -P,) (A)

Inserting equation (12) in equation (13) and solving for the loss components gives:

UA (T..,n Tmb).(24 BOH+ BOH,,) - Qdw (1-RE) (- (15)

Lossconinous + Lossflue _off = F R (15) 24- BOH

By substituting in equation (15) the known parameters from the analytic baseline water

heater, and using equation 13 for BOH,, and equation (A) for BOH, it is possible to calculate the

combined Loss_continuous + LossJlue_offvalues for any of the design options.

E-4

EE-RM-97-900 COMMENT 38TT
References

1. Incropera, F.P, De Witt, D.P., Fundamentals of Heat and Mass Transfer, 2nd ed., John

Wiley & Sons, New York, 1985.

2. McGee, I.E., Dobransky, M. A., and Ingold, K.A., HFC-245fa as a Blowing Agent for

Water Heater Foam Insulation, Bayer Corporation, Pittsburgh, PA, pp. 170-173 in

Proceedings of the Polyurethanes EXPO' 96, sponsored by the Polyurethane Division of

The Society of the Plastics Industry, Inc., Las Vegas, NV, October 20-23, 1996.

3. American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE),

1997 Fundamentals Handbook, p.3.12. Atlanta, GA, 1997.

E-5

EE-RM-97-900 COMMENT 38TT
APPENDIX F: ESTIMATES OF MANUFACTURING COSTS AND ENERGY

CHARACTERISTICS FOR ELECTRIC AND GAS-FIRED

STORAGE WATER HEATERS - DATA FROM MAX MINNIEAR

This Appendix documents the manufacturer cost data for residential electric and gas-fired

water heaters provided to the U.S. Department of Energy by Max Minniear, consultant to

Lawrence Berkeley National Laboratory (LBNL), on May 7, 1998. The data are used in the

Engineering and the Life-Cycle Cost analyses to develop the federal efficiency standards for such

products.

Introduction

The primary source of both manufacturer cost and efficiency data for this analysis was the

Gas Appliance Manufacturers Association (GAMA), which collected data from water heater

manufacturers. GAMA did not provide data for three of the design options being considered (2.5

in. jacket insulation, plastic tank and side arm heater). The missing data were obtained from

Max E. Minniear, former Vice President of Engineering at A. O. Smith Water Products Company

who was recommended by the Gas Appliance Manufacturers Association (GAMA). Mr.

Minniear was contracted by LBNL to provide disaggregated cost and efficiency data for baseline

designs and various design options.

Mr. Minniear's data was used primarily for two purposes: 1) to supply the manufacturing

data for the missing design options, and, 2) to confirm the reasonableness of the computer

models' estimates used in the analysis.

Data

Mr. Minniear provided manufacturer cost and efficiency data for both electric and gasfired water heaters. The data was provided in the format developed by A.D.Little Company to

reflect the basic design options used in the analysis.

Electric Water Heaters: For the typical existing baseline 50-gal electric water heater, Mr.

Minniear provided total manufacturing cost data. Plus incremental manufacturing costs for each

design option.

Table F. 1 contains the manufacturing costs and the associated uncertainty ranges for

electric water heaters and Table F.2 contains the energy characteristics values and the associated

uncertainty ranges.

Gas-fired Water Heaters: For the typical existing baseline 40-gal gas-fired water heater,

Mr. Minniear provided total manufacturing cost data. Plus incremental manufacturing costs for

each design option.

F-I

EE-RM-97-900 COMMENT 38TT
Table F.3 contains the manufacturing costs and the associated uncertainty ranges for gasfired water heaters and Table F.4 contains the energy characteristics values and the associated

uncertainty ranges.

F-2

EE-RM-97-900 COMMENT 38TT
Table F. I Manufacturing Costs - Electric Water Heaters (50-gal)

Cost Uncertainty Cost Uncertainty

Design Options Variable Costs' Range Fixed Costs 2

'3 Range

Variable Costs Fixed Costs

Material Labor Overhead Total (+/- percentage) Capital Product Design Total (+/- percentage)

$/unit $/unit $/unit $/unit Maximum Minimum min. $ min. $ min. $ Maximum Minimum

1 Baseline 58.43 5.77 18.11 82.31 1% 1% 0.00 0.00 0.00 - - 2 Heat Traps4 2.00 0.05 0.15 2.20 1% 1% 0.01 0.01 0.02 1% 1%

3 Increased Insulation (R24 Foam) 5 8.50 0.15 0.45 9.10 5% 2% 0.02 0.04 0.06 3% 2%

4 Increased Insulation (R32 Vacuum) 6 20.00 0.50 1.50 22.00 15% 5% 0.16 0.16 0.32 20% 20%

5 Plastic Tank 7 5.25 0.80 3.20 9.25 5% 5% 0.60 0.12 0.72 10% 5%

The total variable cost includes material, labor and overhead cost. The overhead cost is only the factory overhead

2Conversion cost - millon $/40,000 units

3 There is no fixed cost associated with the existing baseline model

4 The Heat Trap design option cost is assumed to be the same for plastic and metal heat traps 5 R24 which is equivalent to 3 inches of polyurethane foam

6 R32 which is equivalent to a vacuum insulation

7Cost for plastic tank design option reflects the "steel shell/plastic interior" tank method used in the analysis

Table F.2 Energy Characteristics - Electric Water Heaters (50-gal)

DOE Design Options Energy Data Uncertainty Range

EF RE UA On-Cycle Off-Cycle EF

Elec Elec (+/- percentage) (t)

-W W Maximum Minimum

1 Baseline 0.900 0.98 5.50 4400 0 89.5% 87.5%

2 Heat Traps 0.905 0.98 5.25 4400 0 90.7% 89.0%

3 Increased Insulation (R24 Foam) 0.935 0.98 4.00 4400 0 93.7% 90.0%

4 Increased Insulation (R32 Vacuum) 0.955 0.98 3.30 4400 0 96.0% 90.0%

5 Plastic Tank 0.910 0.98 5.00 4400 0 92.0% 90.0%

F-3

EE-RM-97-900 COMMENT 38TT
Table F.3 Manufacturing Costs - Gas-fired Water Heaters (40-gal)

Cost Uncertainty Cost Uncertainty

DOE Design Options Variable Costs 1 Range Fixed Costs 2.3 Range

Variable Costs Fixed Costs

Material Labor Overhead Total (+/- percentage) Capital Product Design Total (+/- percentage)

$/unit $/unit $/unit $/unit Maximu Minimum min. $ min. $ min. $ Maximum Minimum

m

1 Baseline 64.53 6.50 16.72 87.75 1% 1% 0.00 0.00 0.00 - -

2 Heat Traps 4 2.00 0.05 0.15 2.20 2% 2% 0.01 0.01 0.02 2% 2%

3 Increased Insulation (R16 Foam)5 6.00 0.05 0.15 6.20 5% 5% 0.02 0.02 0.04 4% 2%

4 Increased Insulation (R24 Foam) 5 14.50 0.15 0.45 15.10 10% 5% 0.04 0.06 0.10 5% 2%

5 Plastic Tank 7 29.75 2.90 9.25 41.90 10% 5% 0.80 0.40 1.20 10% 5%

6 Improved Flue Baffle 1.25 0.15 0.45 1.85 5% 5% 0.07 0.15 0.22 5% 2%

7 Multiple Flues 13.25 0.65 2.25 16.15 5% 5% 0.75 0.15 0.90 5% 2%

8 Improved Combustion Chamber 0.00 0.00

9 Submerged Combustion Chamber 17.25 1.75 5.75 24.75 5% 5% 0.20 1.00 1.20 8% 4%

10 Flue Damper (electro-mechanical) 6.25 0.70 2.25 9.20 10% 5% 0.03 0.15 0.18 10% 3%

11 Side Arm Heater 24.50 2.10 . 7.20 33.80 20% 10% 0.20 0.50 0.70 20% 10%

12 Two Phase Thermosiphon 12.25 1.15 3.20 16.60 20% 10% 0.04 0.12 0.16 10% 10%

13 IID 14.50 1.25 4.50 20.25 10% 5% 0.07 0.10 0.17 5% 5%

' The total variable cost includes material, labor and overhead cost. The overhead cost is only the factory overhead

2 Fixed costs - min $/50,000 units

3 There is no fixed cost associated with the existing baseline model

4 The Heat Trap design option cost is assumed to be the same for plastic and metal heat traps

5 R16 which is equivalent to 2 inches of polyurethane foam

6 R2 which is equivalent to 3 inches of polyurethane foam

7 Cost for plastic tank design option assumes that the design has a side arm combustion system with the plastic tank as a storage media.

F-4

EE-RM-97-900 COMMENT 38TT
Table F.4 Energy Characteristics - Gas-fired Water Heaters (40-gal)

DOE Design Options Energy Data Uncertainty Range

EF RE UA On-Cycle Off-Cycle EF

Gas Elec Gas Elec (+/- percentage)

Btu/hr W Btu/hr W Maximum Minimum

1 Baseline 0.560 0.75 12.0 40,400 0 400 0 56.5% 54.5%

2 Heat Traps 0.565 0.75 11.5 40,400 0 400 0 57.5% 56.0%

3 Increased Insulation (R16 Foam) 0.576 0.75 10.5 40,400 0 400 0 58.0% 56.0%

4 Increased Insulation (R24 Foam) 0.581 0.75 10.0 40,400 0 400 0 58.5% 56.5%

5 Plastic Tank 0.644 0.80 7.5 40,400 0 400 0 67.0% 63.0%

6 Improved Flue Baffle 0.595 0.79 11.0 40,400 0 400 0 60.0% 58.0%

7 Multiple Flues 0.568 0.80 14.0 40,400 0 400 0 57.5% 55.5%

8 Improved Combustion Chamber

9 Submerged Combustion Chamber 0.583 0.77 11.0 40,400 0 400 0 59.0% 57.5%

10 Flue Damper (electro-mechanical) 0.604 0.75 8.0 40,400 30 400 0 60.6% 58.5%

11 Side Arm Heater 0.637 0.80 8.0 40,400 0 400 0 64.5% 62.0%

12 Two Phase Thermosiphon 0.560 0.75 12.0 40,400 0 400 0 56.5% 54.5%

13 IID 0.565 0.75 11.5 40,000 15 0 5 56.5% 56.0%

F-5

EE-RM-97-900 COMMENT 38TT
APPENDIX G: DESIGN OPTION COMBINATIONS

This Appendix contains a list of all design option combinations for residential electric

and gas-fired water heaters considered in order to develop the final set of designs used in the

analysis to develop federal efficiency standards for such products.

A total of 18 alternative combinations were considered to develop a set of 5 electric water

heater design option combinations. Table G.1 provides a list of all of the alternative

combinations explored for the electric water heaters.

A total of 41 alternative combinations were explored to develop a set of 5 gas water

heater design options. Table G.2 provides a list of all of the alternative combinations explored for

the gas-fired water heaters.

G-I

EE-RM-97-900 COMMENT 38TT
Table G. 1 Corn lete List of Alternative Design Option Combinations - Electric Water Heaters

Design Index Design Option

0 Existing Baseline (14 lb)

I Analytic Baseline (245fa)

2 Heat Traps (metal)

2a Heat Traps (plastic)

3 Increased Insulation (2" foam)

3a Increased Insulation (2" foam) + Heat Traps (metal)

3b Increased Insulation (2" foam) + Heat Traps (plastic)

4 Increased Insulation (2.5" foam)

4a Increased Insulation (2.5" foam) + Heat Traps (metal)

4b Increased Insulation (2.5" foam) + Heat Traps (plastic)

5 Insulted Tank Bottom

5a Insulted Bottom + Heat Traps (metal) + Increased Insulation (2" foam)

5b Insulted Bottom + Heat Traps (plastic) + Increased Insulation (2" foam)

5c Insulted Bottom + Heat Traps (metal) + Increased Insulation (2.5" foam)

5d Insulted Bottom + Heat Traps (plastic) + Increased Insulation (2.5" foam)

6 Plastic Tank

6a Plastic Tank + Heat Traps (metal) + Increased Insulation (2" foam)

6b Plastic Tank + Heat Traps (plastic) + Increased Insulation (2" foam)

6c Plastic Tank + Heat Traps (metal) + Increased Insulation (2.5" foam)

6d Plastic Tank + Heat Traps (plastic) + Increased Insulation (2.5" foam)

Table G.2 Complete List of Alternative Design Option Combinations - Gas Water Heaters

Design Index Design Option

0 Existing Baseline 141 a

1 Analytic Baseline 245fa

la Analytic Baseline 245fa (Resistance to Flammable Vapors Ignition)

2 Heat Trap (plastic)

2a Heat Trap (metal)

3 Increased Insulation (2" foam)

3a Increased Insulation (2" foam) + Heat Traps (plastic)

3b Increased Insulation (2" foam) + Heat Traps (metal)

4 Increased Insulation (2.5" foam)

4a Increased Insulation (2.5" foam) + Heat Trap (plastic)

4b Increased Insulation (2.5" foam) + Heat Trap (metal)

5 · 78% RE (Improved Flue Baffle)

5a 78% RE (Improved Flue Baffle) + Increased Insulation (2" foam)

5b 78% RE (Improved Flue Baffle) + Increased Insulation (2" foam) + Heat Trap

(metal)

5c 78% RE (Improved Flue Baffle) + Increased Insulation (2" foam) + Heat Trap

(plastic)

5d 78% RE (Improved Flue Baffle) + Increased Insulation (2.5" foam)

5e 78% RE (Improved Flue Baffle) + Increased Insulation (2.5" foam) + Heat

Trap (metal)

G-2

EE-RM-97-900 COMMENT 38TT
Table G.2 (cont.)

Design Index Design Option

5f 78% RE (Improved Flue Baffle) + Increased Insulation (2.5" foam) + Heat

Trap (plastic)

6 Electronic Ignition & Electromech. Flue Damper

6a Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2"

foam)

6b Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2"

foam) + Heat Trap (metal)

6c Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2"

foam) + Heat Trap (plastic)

6d Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2"

foam) + Heat Trap (metal) + 78% RE

6e Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2"

foam) + Heat Trap (plastic) + 78% RE

6f Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2.5"

foam)

6g Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2.5"

foam) + Heat Trap (metal)

6h Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2.5"

foam) + Heat Trap (plastic)

6i Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2.5"

foam) + Heat Trap (metal) + 78% RE

6j Electronic Ignition & Electromech. Flue Damper + Increased Insulation (2.5"

foam) + Heat Trap (plastic) + 78% RE

7a Side-Arm Design (Indirect Heating + IID + Metal Tank + Insulation I")

7b Side-Arm Design (Indirect Heating + IID + Metal Tank + Insulation 1" +

HT(plastic))

7c Side-Arm Design (Indirect Heating + IID + Metal Tank + Insulation 2")

7d Side-Arm Design (Indirect Heating + IID + Metal Tank + Insulation 2" +

HT(plastic))

7e Side-Arm Design (Indirect Heating + IID + Metal Tank + Insulation 2.5")

7f Side-Arm Design (Indirect Heating + IID + Metal Tank + Insulation 2.5" +

HT(plastic))

7g Side-Arm Design (Indirect Heating + IID + Plastic Tank + Insulation 1")

7h Side-Arm Design (Indirect Heating + IID + Plastic Tank + Insulation 1" +

HT(plastic))

7i Side-Arm Design (Indirect Heating + IID + Plastic Tank + Insulation 2")

7j Side-Arm Design (Indirect Heating + IID + Plastic Tank + Insulation 2" +

HT(plastic))

7k Side-Arm Design (Indirect Heating + IID + Plastic Tank + Insulation 2.5")

71 Side-Arm Design (Indirect Heating + IID + Plastic Tank + Insulation 2.5" +

HT(plastic))

7m Side-Arm Design (Indirect Heating + Metal Tank + 76% RE)

7n Side-Arm Design (Indirect Heating + Plastic Tank + 76% RE)

G-3

EE-RM-97-900 COMMENT 38TT