NATL INST OF STAND & TECH

A11107

NBSIR 84-2870

Performance and Selection

Criteria for Mechanical Energy

Saving Retrofit Options for

Single-Family Residences

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

June 1984

Prepared for: The Department of Energy

QC Office of Conservation and Renewable Energy

2 3 Q Washington, DC 20585

,1156

34-2870

1934

C. 3
Disclaimer

Any commercial equipment, instruments or materials identified in this paper

does not imply recommendation or endorsement by the National Bureau of

Standards, nor does it imply that the materials or equipment identified are

necessarily the best available for the purpose.
' JIAHOMAL EU71EAU OF . Z . DS

IIFP.AKY

NBSIR 84-2870

PERFORMANCE AND SELECTION

CRITERIA FOR MECHANICAL ENERGY

SAVING RETROFIT OPTIONS FOR

SINGLE-FAMILY RESIDENCES

Esher Kweller

Samuel Silberstein

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Gaithersburg, MD 20899

June 1984

Prepared for: The Department of Energy

Office of Conservation and Renewable Energy

Washington, DC 20585

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler. Director
'
Abstract

Under the Weather izat ion Assistance Program the U. S. Department of Energy

(DoE) provides funds for energy-conserving building improvements in homes of

low- income persons. In proposing to modify the program to also provide funds

for energy-conserving mechanical options, DoE requested that the National

Bureau of Standards investigate energy-conserving mechanical options that may

be suitable for inclusion in the Weather ization Assistance Program. This

report estimates energy savings, and provides performance and selection

criteria, standards, and installed costs for mechanical equipment options for

single-family homes; all from prior studies reported in the literature.

Performance and selection criteria are presented as advantages, disadvantages

and limitations for each option.

Four broad categories of energy-saving mechanical options were investigated:

space heating, water heating retrofit options, heat purrp water heaters, and

recovery of central air conditioner waste heat by desuperheaters. Gas- and

oil-fueled forced-air furnaces and hydronic (hot water) space-heating equipment

were treated in this report.
TABLE OF CONTENTS

Preface

Abstract

List of tables

List of figures Page

1.0. Introduction 1

1.1. Background 1

1.2. Objectives 1

1.3. Scope 1

2.0. Summary of energy-saving mechanical options 1

2.1. Space heating systems 2

2.1.1. Derating with control of excess combustion air

2.1.2. Replacement oil burners 3

2.1.3. Gas conversion burners 3

2.1.4. Vent dampers 3

2.1.5. Reduced excess dilution air 4

2.1.6. Flue gas heat reclaimers 5

2.1.7. Thermostat controls 5

2.1.7 .1. Automatic or manual boiler water temperature reset

control 3

2. 1.7. 2. Setback room temperature thermostats 6

2. 1.7. 3. Fan delay blower temperature control 6

2.1.8. Replacement furnaces and boilers

2.1.9. Electronic pilot ignition devices

2.1.10. Insulating exposed duct work

2.1.11. Zone control 8

2.2. Water heating retrofit options 8

2.2.1. Reduced excess dilution air 8

2.2.2. Reduced thermostat settings 8

2.2.3. Add-on insulation of tank 9

2.2.4. Insulation of distribution pipe 9

2.2.5. Heat traps 9

2.2.6. Vent dampers (see 2.1.4) 10

2.3. Heat punp water heaters 10

2.4. Heat recovery from air conditioners 11

2.5. Maintenance 11

2.5.1. Gas and Oil Fueled Furnaces and Boilers 11

2.5.2. Water Heaters 12

2.5.3. Central Air Conditioning Systems 12

3.0. Recommended approach to retrofit of mechanical options 12

4.0. Space heating system energy saving retrofit options 13
Page

4.1. Derating with control of excess combustion air 14

4.1.1. Gas fueled heating systems 15

4.1.2. Oil fueled heating systems 16

4.2. Replacement oil burners

4.3. Gas conversion burners 19

4.4. Vent dampers 19

4.4.1. Gas-fueled heating systans 20

4.4.2. Oil-fueled heating systems 20

4.5. Reduced excess dilution air 20

4.5.1. Resized vent connector 20

4.5.2. Forced exhaust 21

4.6. Flue gas heat reclaimers 21

4.7. Thermostat controls

4.7.1. Automatic or manual boiler water temperature reset control

4.7.2. Setback room temperature thermostats

4.7.3. Fan delay blower temperature control

4.7.4. Thermostatic radiator valves 23

4.8. Replacement furnaces and boilers 23

4.8.1. Forced-air furnaces 23

4.8.2. Hot-water boilers 23

4.8.3. Determining energy savings from annual efficiency ratings of

furnaces and boilers 23

4.9. Electronic pilot ignition devices

4.10. Insulating exposed duct work

4.11. Zone control 25

4.11.1. Radiator and warm air register covers 2 5 4.11.2. Thermostatic radiator valves (see 4.7.4) 25

5.0. Water heating retrofit options 25

5.1. Reduced excess dilution air (due to reduced size of new water heater)

5.2. Reduced thermostat settings

5.3. Add-on tank insulation

5.4. Insulation of distribution pipe

5.5. Heat traps

5.6. Vent dampers

5.7. Combination Boiler/Water Heaters

6.0. Heat pump water heaters

7.0. Heat recovery from air conditioners/desuperheaters

8.0. Maintenance

8.1. Central Air Conditioners

8.2. Heating systems

iii
Page

8 . 2 . 1 . Oil-fueled furnaces and boilers 32

8 . 2 . 2 . Gas-fueled furnaces and boilers 33

8 . 3 . Water Heaters 33

9.0. Standards 35

REFERENCES 38

iv
LIST OF TABLES Page

l.a Methods of reducing energy losses for heating systems 44

1.

b Design routes to high seasonal efficiency 44

2. Gas conservation potential of various retrofit options 45

3. Oil conservation potential of various retrofit options 46

4. Energy conservation potential of various water heater retrofit

options 47

5. Energy conservation potential of various water heater design changes 48

6. Calculated annual energy and dollar savings and rate of return for

four different water heating systems in four Florida cities 49

7. Calculated annual energy and dollar savings for $100 of annual cost as

a result of increased furnace efficiency 59

v
LIST OF FIGURES

Page

1. Recommended approach for retrofit of space heating systems 51

2. Recommended approach for retrofit of vater heaters 52

3. Part-load efficiency in direct input/output tests 53

4 . Energy flow diagram for a gas furnace system. 54

5. Schematic of air supply and venting in furnace and water

heater 55

6. Schematic of aquabooster water heater with a tankless coil

vater heating boiler 55

7. Diagram of a flame retention head oil burner 56

8. a. Diagram of a boiler with a vent danper 57

b. Diagram of a vent danper installation with a common

venting system 57

9 . a. Diagram of a thermally activated vent danper 58

b. Diagram of an electrically operated vent danper 58

10. Diagram of the flow paths in a flue gas heat recovery

system 59

11. Example of one type of flue gas heat recovery system 60

12. Diagrams of heat traps 61

13. Diagram of heat purrp water heater with integral condenser 62

14. Diagram of a separated type of heat pump water

heater with add-on condenser 62

15. Diagrams of an electric resistance water heater without

and with a waste heat recovery unit 63

16. Monthly coefficient of performance of four different

water heating systems in four Florida cities 64

17. Effect of regrigerant overcharge and undercharge on

performance of central air conditioning system 65
PERFORMANCE AND SELECTION CRITERIA FOR MECHANICAL ENERGY

SAVING RETROFIT OPTIONS FOR SINGLE-FAMILY RESIDENCES

1.0. Introduction

1.1. Background

Under the Weather ization Assistance Program [1] established by the Energy

Conservation in Existing Buildings Act of 1976 [21 , the U. S. Department of

Energy provides funds to install insulation, storm windows, caulking,

weatherstripping, and other iirprovements to the building shell, in order to

conserve energy in homes of low-income, particularly elderly and

handicapped, persons. The Department of Energy is now proposing to modify

the program to make it more "balanced" [3] , that is to also provide funds

for energy-conserving mechanical options.

1.2. Objectives

The Department of Energy requested that the National Bureau of Standards

identify energy-conserving mechanical options that may be suitable for

inclusion in the Weather ization Assistance Program, estimate their energy

savings, and provide performance and selection criteria. This is done in

this report for single-family homes; results for multiple-family homes are

reported separately.

Lt.3. t - Scope

The energy-savings estimates of mecahnical options, and performance and

selection criteria were derived from prior studies reported in the

literature. Performance and selection criteria are presented as advantages,

disadvantages and limitations for each option. Since selection criteria

depend upon local codes, circumstances such as equipment age, and local

fuel and electricity costs, decisions as to which options to be used should

be made at the local level.

Standards concerning equipment and its installation are listed for each

option, as are installed costs. Some equipment costs are also given for

new commercially available products that may not have been previously

reported. Payback times are outside the scope of this report, but are

included if they are available in the literature.

Section 3 recommends the order in which these options should be considered.

A more detailed description of each products' energy savings alone, and in

some cases in combination with other options is presented in Sections 4 to

7 together with references.

2.0. Descriptions of and selection criteria for energy-saving mechanical

options

Four broad categories of energy-saving mechanical options were

investigated: space heating, water heating retrofit options, heat pump

water heaters, and recovery of central air conditioner waste heat by

1
desuperheaters. Gas- and oil-fueled forced-air furnaces and hydronic (hot

water) space-heating equipment were treated in this report. Following in

this section are brief descriptions of these options and estimated energy

savings potential where such data are available.

2.1. Space-heating systems

Before investing in retrofit equipment for a furnace or boiler, the heat

exchanger should be examined to ensure that it is not defective.

Guidelines for inspecting the heat exchanger are in section 8.2.2.

2.1.1. Derating with control of excess combustion air

Derating reduces the rate of fuel and air admitted to a burner. Derating

is done for the purpose of providing a better matching of the maximum heat

output of the furnace or boiler to the design heating requirement. Approval

of this option is dependent upon local codes. Manufacturers of gas

furnaces and boilers do not encourage derating, and it may nullify their

warranty.

Advantages

Energy savings averaging 9% have been reported for gas-fueled heating

systems. For oil-fueled heating systems, energy savings are 8.7% in forced

air systems, and 2.6% in hot water systems.

Off-period losses are decreased by the reduced number of burner cycles.

On-period combustion efficiency may increase.

Little or no material cost is required for derating gas-fueled equipment.

Dis^dvehtaggs/iMtatj-png

Derating may void warranty of gas-fueled furnace.

Derating may violate local building codes.

Derating could lead to severe safety problems unless done by qualified

personnel, especially for gas furnaces.

Derating may reduce life of heat exchanger (especially counterflow type) in

gas-fueled furnaces.

Derating should be limited to not more than 40% of maximum rated input to

avoid condensation problems.

Replacement of the combustion chamber liner may be required in order to

improve the efficiency of oil-fueled equipment.

Derating is not applicable to boilers equipped with domestic water heating

coil (unless a separate hot water storage tank is used).

Field tests showed no savings with steam-boiler systems.

2
2.1.2. Replacement oil burners

Flame retention head burners use a fuel-air mixture that requires less

excess combustion air than conventional burners.

Advantages

For oil-fueled boilers, energy savings over 20% have been reported. For

oil-fueled furnaces, energy savings of 8% have been reported.

Replacement burners save the cost of replacing entire furnaces,

particularly when several years of life remain.

Disadvantages/limitations

Incompatibility of the more intense combustion or smaller flame size may

require the combustion chamber to be modified.

2.1.3. High efficiency gas conversion burners

Many old coal-fired heating systems have been converted to heat with gas by

replacement with gas conversion burners, most likely atmospheric type.

Since 1979, powered gas conversion burners have been marketed. Converting

from old atmospheric to powered gas conversion burners saves energy because

the newer burner operates with less excess combustion air. Recently, oilfueled furnaces and boilers have been converted to gas (where the cost of

fuel oil was disproportionately higher than gas). These burners are most

likely to be the powered type.

Advantages

Newer powered gas conversion burners offer higher combustion efficiency and

reduced off-period loss as a replacement for older atmospheric-type gas

conversion burners. Powered burners offer flexibility of derating to a more efficient firing rate. Combustion efficiency improvement of 15% has

been reported at steady-state operation. The installed part-load

efficiency improvement would be even better since off-period loss is

reduced with a powered burner.

Disadvantages/limitations

May not be advisable for older equipment with deteriorated heat exchanger

having limited remaining life.

2.1.4. Vent dampprs

A vent damper is an electromechanical ly or thermally operated valve

installed between the draft diverter and the vent connector with a movable

plate that closes to prevent heat loss during heating system off-cycles.

Vent dampers for water heaters are similar to those for space-heating

systems

3
Advantages

Reduced off period losses for all types of danpers installed indoors.

For gas-fueled heating systems, energy savings averaging 5% have been

reported

For oil-fueled heating systems, energy savings averaging 8-9% have been

reported

Thermal-type vent dairpers offer the possibility of low-cost installation.

Disadvantages/limitations

Full potential savings can only be achieved if furnace or boiler is

installed in an area coirarunicating with the heated area of the home (that

is, not as useful if furnace is in attic or crawl space).

Installation can lead to severe safety problems unless done by qualified

personnel

A water heater vented through a common stack with the furnace should also

be equipped with a stack dairper to maximize savings.

2.1.5. Reduced excess dilution air

In many homes retrofitted to reduce heat loss or with thermostat setback,

the furnace may either be replaced with a smaller unit or the input rate

reduced to better match the new heating requirements (as described under

Derating) . Consequently, the venting system will be oversized. It may

have been oversized with the original furnace as well. This results in

excessive stack draft. Hie consequent flow rate of heated room air out the

stack is considerably greater than needed for flue gas dilution. This is

particularly true for older homes with tall masonry chimneys which are

generally larger in cross-sectional area than factory-built chimneys.

Reduced excess dilution air at the draft control device can be achieved in

gas-fueled equipment by reducing the cross-sectional area of the vent

connector. Excess stack draft can also be reduced by using a small section

of pipe in the vent connector with reduced cross-sectional area, without

replacing the entire vent connector pipe.

Mvmtages Low cost of materials for resizing vent connector pipe.

Reduced on- and off-period infiltration losses.

Energy savings of 3.7% have been reported for gas-fueled heating systems.

Disadvantages/limitations

Installation can lead to severe safety problems unless done by qualified

personnel

4
2.1.6. Flue gas heat reclaimers

Flue gas heat reclaimers are devices that capture heat that would normally

be exhausted out the flue.

Advantages

Energy savings of 6.6% have been reported for gas-fueled heating systems

and 10% for oil-fueled furnaces. New designs using water spray to recover

stack energy claim even greater savings.

Flue-gas heat reclaimers offer an alternative solution to saving energy

when stack loss cannot be reduced by increasing existing burner efficiency

by tuneup or reduced input rate.

Disadvantaaes/limitations

Most effective type of heat extractor is relatively expensive,

approximately $600 plus installation cost. Therefore use of this option

should be based on expected remaining useful life of the furnace heat

exchanger

Installation should be done only by qualified personnel properly trained.

Space limitations in the furnace room could restrict some installations.

2.,1 ,7« Thermostat controls

2. 1.7.1. Automatic or manual boiler water temperature reset control

Automatic boiler temperature reset control allows for using a boiler water

temperature which more closely matches the amount of heat needed to

maintain comfortable room temperature for a given outdoor air temperature.

This controller automatically raises the circulating boiler water

tenperature set point as outdoor temperature drops, and reduces the water

temperature setting in milder weather. Energy is saved due to reduced

cycling of the burner, and less heat is lost out the stack during the off

period. (This is particularly iirportant in the absence of a stack damper

J

This is particularly applicable for systems which maintain boiler water

temperature to independently heat several zones with the same hot water

boiler (usually two or more separate zones or apartments).

Advantages

Reduces off-period losses. Energy savings of 10% have been reported.

Manual reset is a simple adjustment.

In homes with too few radiators, the boiler output is excessive and the

boiler cycles on the high limit control, wasting energy. If it is

possible, the number of radiators should be increased. If this is not

possible, reducing the boiler water tenperature would reduce short cycling.

5
Disadvantages/1 imitations

Most effective type (automatic reset control) is expensive.

Not applicable when domestic water heating coil is used.

Reducing water temperature too low could cause excessive condensation on

heat up on the flue gas side and reduce heat exchanger life.

2.1.7 .2. Setback room temperature thermostats

Setback thermostats are thermostats that allow different temperatures to be

set for different times of the day or night. Manual reset can achieve the

same results but is less likely to be practiced diligently.

Advantages

For homes with oil-fueled boilers, energy savings of 9% have been reported

(8% for gas furnaces with 3°C (5°F) night setback).

Disadvantages/limitations

Setback is limited by the possibility of pipe freezing. This can be

corrected by using electric heating tape and piping insulation for remote

areas or where water pipes pass through less heated areas of the house.

For the very young and old, setback may not be safe or comfortable.

2.1.7 .3. Fan delay blower temperature control

Fan delay blower tenperature control adjustment both after burner turn-on

and shut-down can be optimized without compromising comfort to recover heat

that would otherwise be lost out the stack.

Advantages

Setting the fan delay blower temperature control is a simple adjustment

requiring no additional materials.

Gas energy savings of 6800 MJ/year (64 therms/year) has been reported.

Electricity use has been reported to typically increase by 610 MJ/year (170

kWh/year) since the blower motor must operate longer. However, with

utility rates of $0.0066/MJ ($0.70/therm) for gas and $0.017/MJ ($0.06/kWh)

for electricity, savings amount to $35/year without need for any equipment

and minimal labor cost. (Hie adjustment can be accomplished on some units

with a screwdriver, and on most units by moving a manual control dial.)

Disadvantages/limitations

Not as effective where electricity costs are high because requires

additional electricity to operate fan motor.

6
2.1.8.

Replacement furnaces and boilers

Furnace or boiler replacement may be justified if the present furnace is

oversized, operates at low efficiency, and cannot be derated. If the heat

exchanger is defective, the entire furnace or boiler must be replaced.

Section 4.8 includes methods for estimating oversize, and for estimating

expected energy savings of furnaces and boilers with a known annual

efficiency.

Advantages

Recently, a wide variety of new equipment, especially gas furnaces and

boilers, has become available that achieves much higher efficiencies, and

hence energy savings, than even well-tuned older equipment. Additional

savings may result because replacement equipment also allows proper sizing,

which may not always be possible for older equipment.

Disadvantages

The cost of an installed new unit, especially a boiler, may exceed the

guidelines of the weatherization program in areas with high labor costs

(see section 4.8.1 for expected costs).

2.1.9. Electronic pilot ignition devices

Intermittent ignition devices ignite gas to begin the combustion on-cycle,

eliminating the need for a constantly burning pilot light.

Advantages

Energy savings of 4.4% have been reported. Greater savings apply if

central air condtioning is used at the same time as a constantly burning

pilot is operating.

Disadvantages/limitations

There are no energy savings in replacing the pilot if the pilot is turned

off for the non-heating season.

Installation can lead to severe safety problems unless done by qualified

personnel.

2.1.10. Insulating exposed duct work

Insulation of exposed duct work saves energy both during the heating and

cooling seasons (with central air conditioning). Exposed ductwork in

unheated basements, crawlspaces, and attics are important. Before

sheetmetal is insulated, any leaks at the seams of the duct work should be

covered with duct tape.

7
Advantages

Insulation of exposed ducts in unheated areas can reduce heat loss. Energy

savings of up to 2.6 W/m2,°C (1.5 Btu/h*ft2 *°F) , or 40% of the heat output

of a furnace, have been reported for the not uncommon condition of leaking

ducts

Cost of insulation and labor is small compared to the potential energy

savings

Disadvantages/limitations

It may not be possible to insulate inaccessible duct work.

2.1.11. Zone control

Radiator valves for hydronic systems — either manual or thermostatcontrolled — permit each radiator to be individually controlled.

Alternatively, radiator and warm air register covers can be used in

unoccupied rooms.

Advantages

Energy savings up to 40% have been reported.

Added radiator controls are not expensive, and result in not heating little

used areas of the house.

pisadyah.tagg.sZl imj.tat.ipns

Installing zone control is expensive for forced-air systems.

2

.2..

. Water heating options

2,2-J.-.. .Reduced excess dilation air

Whenever a water heater is replaced by one with a smaller burner input

capacity, or when venting system is oversized, space-heating energy can be

saved by reducing excess dilution air (see 2.1.5 for more details).

2.2.2., Raduc_edj^e.nnp.stat gettings

Hot water storage temperature can be reduced by reducing the thermostat

setting

Advantages

Energy savings up to 12% have been reported.

Unskilled personnel can adjust thermostats on all types of water heaters.

8
Disadvantages/ 1 imitat ions

Ihemostat settings cannot be reduced where there are automatic dishwashers

that do not preheat water, since they require an inlet water teirperature of

60°C (140°F)

2.2.3. Add-on insulation of tank

An insulated blanket cover over the water-heater jacket may reduce water

heater jacket losses.

Advantages

Savings up to about 9% have been reported.

Insulated blanket covers cost little for all types of water heaters.

Disadvantages/ 1 im^jons

There are no disadvantages in using insulated blanket covers on electric

water heaters. Because the stack loss of gas-fueled water heaters amounts

to 50% of the standby loss, jacket loss savings are less than for electric

water heaters.

2.2.4. Insulation of distribution pipe

Uninsulated hot water pipes lose heat both when hot water is being drawn or during standby.

Advantages

Three percent of the energy used to heat water can be saved by insulating

the first 7.6 m (25 ft) of distribution pipe.

This option is particularly advantageous where hot water pipe passes

through unheated areas or where hot water continuously circulates in larger

buildings with long piping runs.

Disadvantages/limitations

Some pipes may not be accessible for insulation.

2.2.5. Heat traps

Heat traps are curved sections of pipe that brake the natural tendency of

heat to rise out of a water heater.

Advantages

Heat traps can save energy at a rate of approximately 17 W per water

heater. Savings would be lower if riser pipes are insulated.

Heat traps involve low cost for materials.

9
Disadvantaaes/1 imitat ions

Heat traps require replumbing inlet and outlet lines. Therefore

installation is only justified if done at the same time as water heater

replacement. Insulating the pipe could probably save as much energy as

heat traps.

2.2.6. Vent dampers

Vent dampers for water heaters are similar to those for space-heating

systems. A double danper which closes at both the flue and the draft hood

outlet has been approved for residential gas water heaters (under the

classification "mechanical dairpers") but is not being marketed at present.

Advantages

If both the water heater and furnace are located in a heated area, gas

savings can be as high as 4700 MJ/year (45 therms/year) for both.

A thermal stack damper is easy to install on a gas-fueled water heater

since it does not require an electric hookup.

Disadvantages/limitations

Vent dampers save little energy in regions with a mild heating season,

because energy recovered at the water heater does not greatly reduce space

heating load.

Only thermal vent dampers can be installed on gas-fueled water heaters

because water heaters don't have the necessary electrical wiring for

electrical dairpers.

Installation can lead to severe safety problems unless done by qualified

personnel.

2.3. Heat puiip water heaters

Heat pump water heaters are normally considered as replacements for electic

water heaters. Heat pump water heaters transfer heat from the air in the

room surrounding the device into the water tank, using a vapor-conpression

cycle similar to that of a window air conditioner.

Advantages

Heat punp water heaters typically save 47% of the electricity used to heat

water, or 10,500 MJ/year (2917 kWh/year).

Heat punp water heaters help reduce cooling load in areas with long cooling

seasons

Heat punp water heaters located in basements dehumidify basement air.

10
Disadvantaaes/ 1 imitations

The high cost ($800-1200) would limit the applicability of heat purrp water

heaters to areas where high electric rates justify the initial cost.

Heat pump water heaters should be installed in well-ventilated areas in

order to avoid lowering the teirperature of the air surrounding the unit.

2.4. Heat recovery from air conditioners

A desuperheater heat recovery unit transfers heat from superheated

refrigerant in an air conditioner to a water tank via a heat exchanger.

Advantages

Energy savings are estimated to be 2900-4300 MJ/year (800-1200 kWh/year).

This amounts to $40-60/year assuming electricity costs of $0.014/MJ

($0. 05/kWh)

Desuperheaters save energy in homes using central air conditioning systems

for long periods. They may also inprove central air conditioner operating

efficiency.

In the southern half of the United States, it may be possible to disconnect

the electric power to the water heater at the start of the cooling season,

heating water during the summer conpletely with waste heat from the central

air conditioner.

Disadvantaaes/limitations

Large energy savings at the water heater are predicated on extensive use of

the central air conditioner. The ability to reduce central air

conditioning use by substituting whole house fans for cooling would

probably save more energy than desuperheaters would recapture.

2.5. Maintenance

Maintenance of furnaces and boilers, water heaters and central air

conditioning systems is described separately below, followed by common

advantages and disadvantages/ limitations.

2.5.1. Gas- and oil-fueled furnaces and boilers

Replacement of air filters and removal of dust from the fan conpartment are

recommended to maintain the air flow rate, and therefore the heat transfer

rate, at their design levels. Others checks on operation, as detailed in

the National Fuel Gas Code for gas furnaces, are important for safe

operation. Cleaning of combustion chambers and heat exchangers is required

to maintain proper operating efficiency of oil-fueled equipment. Soot

buildup due to poor combustion is a cause of efficiency degradation in oilfueled equipment.

11
2.5.2. Water heaters

Silt and scale should be removed from storage tanks of all water heaters.

The comments about oil-fueled furnaces and boilers apply to oil-fueled

water heaters as well.

2.5.3. Central air conditioning systems

Replacement of air filters, cleaning indoor and outdoor heat exchanger

coils, and proper refrigerant charge are recommended for central air

conditioning systems.

Advantages lot maintenance furnaces and toi lers., water heaters and

central air. conditioning systems)

Maintenance may save energy, inprove comfort, reduce incidents of failure,

and identify unsafe operating conditions.

pisadyantagesZlimj.tat.iQns

There are no disadvantages or limitations to proper maintenance.

3.0. Recommended Approach to Retrofit for Mechanical Equipment Potions

In section 2 the various mechanical options presented were not presented in

sequence in which they should be done. However, when approaching heating

equipment for retrofit there is a logical order of proceeding. Since there

are many possible variations for installations across the country there

will also be variation to the approach presented here. A change of fuel

type with replacement of equipment has not been considered here. It is

assumed that type of fuel in use would continue as presently in use.

An approach for all types of space heating systems is presented as a flow

chart in figure 1. and for water heaters in figure 2. Figure 1. begins

with the two most common retrofit options which are applicable to all types

of heating systems - insulation of the heat distribution ductwork or

piping, and installation of a night setback thermostat. After these are

completed, an examination of the furnace or boiler heat exchanger is

recommended before proceeding with any further retrofitting. If the heat

exchanger is defective as determined by the presence of combustion products

through the heat exchanger in a hot air system or of water leaking in a

boiler, then retrofit of that equipment should not be attempted and the

unit should be replaced. If the heat exchanger is in good condition, the

approach to retrofitting should be as shown in figure 1. for the heating

systems. In that figure the words "consider installation" are used because

the type of installation and the heating systems physical location may

control the applicability of specific options. For example, it would not

be prudent to install a vent danper on a furnace which is either installed

outdoors or does not communicate in any way with a heated area of the home,

(i.e. an unheated garage, a crawl space or an attic). It is also not

prudent to install electric ignition on a gas furnace in a unit where the

occupant is capable of and diligently turns off the pilot during the nonheating season and relights the pilot without assistance.

12
For vented room heaters, which may be the type of heating system used in

milder climates, the options that apply are simply to check combustion, and

adjust the combustion air if necessary to increase efficiency to 70%, and

to consider installation of a vent damper. On most room heaters, a vent

damper would be justified since it is installed in the room being heated.

It would not be appropriate for a floor furnace installed in a crawl space.

One type of water heating system which has not been included in figure 2 is

the combination boiler/water heater? also referred to as the tankless coil

type system. It has been shown that considerable space heating energy

savings can be achieved by using an add-on tank to that system in order to

allow for derating when an oil burner is used. In addition, considerable

water heating/energy savings can be achieved by substituting a tank type of

water heater for use during the non-heating season, and shutting down the

boiler during that period. See section 5.7 for further details.

The only options being considered for the central air conditioning/heat

pump systems is maintenance, which can be a very important option to saving

energy for those systems. See section 8.1.

Each pertinent sub-section of sections 4 and 5 should be referred to as

indicated in figures 1 and 2 before a decision is made on which type of

retrofit is to be used.

4JL. Space heating system energy saving retrofit options

Normal operation of heating systems wastes energy in several ways. For

example, Brookhaven National Laboratory [4] found that operating stack

losses accounted for 15-35% of the available heat in the oil, operating

jacket losses 0-10% and off-cycle losses 5-15%. Brookhaven National

Laboratory found that seasonal (annual) overall efficiency of oil-fueled

boilers ranged from 55% to 75%. Efficiencies above 80% are now attainable

by retrofitting both gas- and oil-fueled heating systems.

Energy can be saved in residential heating systems by raising burner

efficiency, minimizing heat lost up the chimney (operating stack loss),

heat lost through the boiler casing or furnace to its surroundings during

burner operation (operating jacket loss) , and heat lost when the burner is

not operating (off-cycle losses).

Improved steady-state efficiency is far from the whole story, however.

Much wasted heat is lost during off cycles. Therefore, overall heatingsystem efficiency at part load, more than steady-state efficiency,

determines seasonal efficiency [5], Figure 3 shows the effect of burner

on-time on seasonal efficiency of boilers having conventional and flame

retention head oil burners, and standard and improved boiler heat exchanger

surfaces. Table 1 and figure 4 show the factors that affect seasonal

efficiency, and design routes to raise seasonal efficiency.

Estimates of energy saved by the mechanical options described in this

report are derived from what are believed to be the best available sources. Field test results are considered preferable to laboratory investigations,

vfaich are in turn considered preferable to computer simulations. It should

be borne in mind that energy savings are mean values of population

distributions whose range can often be twofold. Details of these energy

savings distributions can be seen in sane of the references cited.

13
Before beginning any major retrofit to a furnace or boiler, an examination

of the heat exchanger is recomended in order to confirm that it is not

defective. Section 8.2.2 includes guidelines for check i no the beat

exchanger.

4.1. Derating with control of excess air

Derating is done for the purpose of providing a better matching of maximum

furnace or boiler heat output to the design heating requirenent. Oversized

systems cycle more frequently than properly sized systems because they

provide excess heat. Each time the system is turned on, heat must be

provided to bring it up to operating temperature. When it is turned off,

residual heat remaining in the heat exchanger is lost out the open stack

(if a stack damper is not used). Derating reduces the rate of fuel and air

admitted to a burner, reducing cycling frequency. It is not an acceptable

option if it violates local building codes.

There are several reasons why houses may have oversized heating systems.

They might have been deliberately planned as a safety factor; changes in

the house, for example conservation measures, might have lowered the

heating requirement since the heating system was installed; heating load

might have been improperly calculated [6].

Derating may increase comfort because it reduces the number of hot-cold

cycles corresponding to heating system on-off cycles. Derating does,

however, increase the probability of heat exchanger corrosion. Because

fans operate when the heating system is on, and derated systems are on

longer than unmodified systems, electrical use is slightly increased [6].

Derating a heating system must be weighed against replacing present

equipment with properly sized equipment. If the heating system is in poor

condition, replacement may be a better option. (Criteria and procedures

for installing new oil burners are described by the National Bureau of

Standards and the Department of Energy [7].) Cptimum oversize is between

50 and 60% because this extent of oversize is required for recovery from

night setback [8],

Oak Ridge National Laboratory [9] estimates that gas-fueled furnaces

oversized by a factor of two require 8-10% more gas than properly sized

furnaces.

The American Gas Association [10] describes a detailed method for

calculating fuel input requirements for design conditions. The procedure

requires knowledge of gas consunption based on gas bills for four months of

the previous heating system. A simpler, less detailed procedure is

presented by the "Consumer reports money saving guide to energy in the

home" [11] for oil furnace derating; the authors do not recommend derating

of gas furnaces. However, the procedure is considered here to be

applicable to any type of heating system and fuel. One measures the

furnace burner on time during at least one hour and derives a size factor

by a calculation that accounts for the temperature differences between that

time and the design day. From the design factor, one determines whether

the furnace input rate is large enough to derate. A "Procedural guide to

derating gas appliances" is included in the "AGA manual for field service

14
and adjustment of gas space heating equipment" [61.

4.1.1. Gas-fueled heating systems

Manufacturers of gas furnaces and boilers do not encourage derating, and it

may void their warranties.

Gas heating appliances may be derated by reducing the size of main burner

orifices, reducing gas pressure, or both, Ihe American Gas Association [6]

states that reducing orifice size is generally safer than reducing

pressure, and that the frequency of ignition problems increases when the

design pressure of the burner is altered.

Derating by itself would increase the amount of excess air and reduce flue

gas temperature because less gas would be burned than before derating.

Consequently, little or no energy would be saved. Internal flue

restriction by baffling the heat exchanger is required to restore carbon

dioxide concentration — or equivalently, control excess combustion air —

to the same levels as before derating. Figure 5 shows the entry points of

combustion and dilution air in a furnace and water heater.

The Gas Industry [12] performed a conservation study, the Space Heating

Efficiency Improvement Program (SHEIP), on 2650 North American houses over

three years. The results are shown in table 2. It can be seen in table 2

that derating gas without derating combustion air reduces gas use by only

1.5%. In combination with flue restriction, that is, control of excess

combustion air, derating fuel reduces gas consumption by 6.2%.

A detailed analysis of 65 of the SHEIP houses [13] was used to derive

approximate regression relationships between expected fuel savings due to

derating fuel and change in furnace steady-state efficiency, fuel input

derate and vent area restriction. The relationships ares

for furnaces alones

AC = 0.42 AE + 0.19AD + 0.03 AV

for boilers alone:

AC = 0.68 Ae + O.ll^D + 0.05 Ay

for furnaces and boilers:

AC = 0.48 AE + 0.16AD + 0.03AV

where

AC = percentage change in gas consumption

aD = percentage change in fuel input derate

AV = percentage change in furnace vent open area restriction

AE = percentage change in steady-state efficiency

15
As can be seen, change in furnace steady-state efficiency is the most

important factor in this study. However, derating and vent restricL.xOi, ae

required for inproved efficiency.

One potential negative aspect of derating gas furnaces has been the

potential for accelerated heat exchanger corrosion due to condensate (which

is acidic) deposits due to lower flue gas temperatures (possibly below the

dew point on cold spots) . Rochester Gas and Electric Company derated more

than 60 residential gas furnaces in 1977. The conclusions of that study

(14) were that, with regard to corrosion and furnace derating:

o Furnace design is iirportant.

o Indoor contaminants may be important.

o Approximately 50% of the derated furnaces were in good condition after

four years.

o Some furnaces corrode too much whether you derate them or not.

In that study, it was found that furnaces were 50 - 150% oversize in

Rochester. The derate procedure used included reducing the speed of the

blower so that the cooling effects of the combustion chamber was reduced.

This would tend to make any heat exchanger cold spots warmer.

This Rochester Gas and Electric Company (RG&E) program of derating was

offered to the public in 1977 on a limited basis via trained local heating

contractors. Homeowners paid $142 to have their central heating systems

derated. This program resulted in an average 15% reduction in gas fuel

usage for equivalent total number of degree days. The savings ranged from

2% to 37%. Details of the RG&E study includes a selection procedure used

to identify potential sites for retrofit and discussion of the training of

contractors. See Ref. (15).

-4.1.2. Oil-fueled heating systems

Honeywell [16, 17] analyzed reductions in oil use in 26 New England homes

in which burners were derated by having their nozzle sizes reduced. Firing

rates were reduced an average of 27%. Average seasonal oil savings were

8.7% in forced air systems, 2.6% in hot water systems, and energy use

increased in steam systems. (Steam systems consume an insignificant

quantity of energy in the UJS. compared to other residential heating systems

J

Walden Research [18] reduced the firing rates of 18 oil-fueled heating

systems by an average of 36% and obtained average seasonal fuel savings of

14%. Steady-state efficiency was increased from 69% to 76%.

Walden Research [18] installed reserve domestic hot water storage tanks

("aquaboosters"; see figure 6) in eight hot-water systems with tankless

coils for domestic water heating. Without this retrofit, firing rate could

not be lowered below 4.75 1/h (1.25 gal/h). Below that rate, enough hot

water could not be delivered. This retrofit made it possible to reduce

firing rate an average of 34%. Average seasonal fuel savings were 12% and

average steady-state efficiency increased from 71% to 76%. The effect on

16
the hot water energy requirement of this retrofit for the summer months was not evaluated by this study.

Brookhaven National Laboratory [4] found that overall efficiency of oilfueled furnaces increased from 72% when the burner was on 10% of the time,

to 82% when the burner operated continuously.

A procedure for optimizing nozzle size is described in "A service managers

guide to saving energy in residential oil burners" [19] and in "A guide to

efficient oil heating in homes" [20],

42. Replacement oil burners

Flame retention head burners (figure 7) provide an atomized fuel-air

mixture that requires less excess combustion air than conventional burners.

Because flames are hotter, heat transfer and combustion performance are

improved [21] . Smoke and pollution are claimed to be reduced almost to

zero [22]. Air flow rate, and therefore heat losses, during off cycles are

reduced because the burner offers more flow resistance during the off

cycle.

Routinely installed retention head burners save 11% of fuel oil annually,

while optimally installed burners save 18%. Optimal fine tuning included

sealing off air leakage, cleaning the heat exchanger and combustion

chamber, reinsulating the boiler and adjusting the draft. Routine tuning

consisted of annual maintenance, including cleaning. In both cases,

combustion chambers were repaired or replaced as necessary. Routinely

installed burners cost $325-425 in 1981. Optimally installed units cost

$390-425. Replacement combustion chambers cost an additional $60-100.

Brookhaven National Laboratory [4] tested seven different kinds of oilfueled flame retention head burners. These burners operated at seasonal

efficiencies of 70-75%, compared to 56% for a conventional burner. Stack

losses were reduced from 21% for the conventional burner to 12-18%. Jacket

and off-cycle losses were also reduced. Annual oil use was reduced 17-23%,

from 5320 L (1405 gal) to 4110-4390 L (1087-1161 gal).

Oil-fueled furnaces were also tested. Combustion chambers were routinely

relined and the heat exchangers were cleaned prior to burner installation.

Firing rates were reduced and the equipment was properly tuned. The

furnace recirculating fan control was adjusted to start fan operation as soon as possible after the burner started, and to maintain fan operation as long as possible after burner shut-down. The burner refit test produced

typical annual savings of 8%. The burner cost $460, including the new

combustion chamber liner. Retention head burners increased steady-state

efficiency from an average of 68% to an average of 78% in 22 oil-fueled

furnaces. In 17 houses using retention head burners in combination with

vent dampers, the steady-state efficiency was 77%.

Installation of seven new flame retention head burners, with firing rates

reduced an average of 43%, produced average seasonal fuel savings of 30%.

Excess air was reduced by 52%, and steady-state efficiency increased 29%

[18]

The Department of Energy [23] retrofit 200 heating systems of low income

17
families with flame retention burners. Hie purposes of the study were to

test whether the high savings found by Brookhaven National Laboratory could

be duplicated in typical low income homes, and to develop an

administratively sinple program. Average fuel use reduction of just over

20%, compared to conventional burners, was achieved. Administrative

simplicity was achieved by paying contractors a fee of $500 to raise

steady-state burner efficiency to 80%. Hie program was since expanded to

over 11,000 homes in different regions of the United States.

Oak Ridge National Laboratory [24] reported that installation of a

retention head burner in a home eligible for low-income weather izat ion

assistance cost approximately $400 and reduced fuel requirements by 18% on

average. Oak Ridge further estimated that because furnaces eligible for

veatherization are older and presumably less efficient than typical

furnaces, and because the firing rate of the burner can be reduced

simultaneously, burner replacements done under the weatherization program

are likely to produce energy savings of 20% or more.

Guidelines for, and a discussion of, replacement criteria, selection and

installation of r eplacement burners, and post-installation prodedures can

be found in reference [7]. Specific installation instructions for five

manufacturers' flame retention head burners are given in reference [201.

Hie NBS Special Publication No. 606 (7) includes the following criteria:

Replace the burner only if the estimated savings resulting from

installation of a more efficient burner will pay for the cost of the

replacement burner. If the savings calculated, multiplied by the

homeowner's desired payback period in years exceed the total cost of

burner replacement (labor plus parts) , the burner should be replaced.

Table 7 shows the annual dollar savings per $100 of annual fuel costs that can be achieved by increasing furnace efficiency.

Another set of criteria for replacing oil burners is given in (47), where

the following reasons are given for replacing an oil fired burner:

o Low Combustion Efficiency

Replace if after adjustment and tune up, steady state effiency could

not be raised above 60%.

o High Smoke Levels

Replace if the steady state efficiency after tune-up is between 60% -

70% with the smoke number in excess of 3 on the Bachrach scale.

o Inability to Reduce Firing Rate

If the reduced firing rate adjustment procedure results in shifting to

larger and larger nozzle sizes until the original size is again

reached the burner should probably be replaced.

18
4.3. High efficiency aas conversion burners

Many coal burners were converted to gas-" or oil-fueled burners twenty-five

or more years ago. The gas burners used then were atmospheric with

continuous pilot burners. High efficiency power burners are available

today which can improve both steady-state and seasonal efficiency. Power

burners can also be equipped with spark ignition systems rather than

continuous pilot burners. The tight construction of power burners reduces

the air flow rate through the burner section, reducing off-period stack

losses. Power burners can be derated to the proper heat input rate for a

given heating load, whereas it nay be impossible to effectively derate the

old atmospheric gas burner. Consumers Union [113 tested and compared the

efficiency of a power conversion and atmospheric burners; combustion

(steady-state) efficiencies were 79-83% for power burners compared with 74%

for atmospheric burners.

-4A. Vent dampers A vent damper is a valve installed between the draft diverter and the vent

connector of a gas- or oil-fueled combustion applicance, with a movable

plate that closes to prevent heat loss during burner-off cycles.

Flue gases must be vented outdoors to maintain occupant health, safety and

comfort. Flue gases are vented through a chimney by the tendency of hot

gases to rise. This means that a certain amount of heat retained in the

metal of the heat exchanger is lost out the open vent when the burner

cycles off. Because a 70% oversized burner in a heating appliance

typically cycles on and off about 17,500 times per year, this can be a significant loss, and more so with units that are oversized to a greater

extent. The amount of lost heat can be minimized if the stack is equipped

with a damper that constricts the flow of flue gases vhen the main burners

are off [63

Because a vent damper is located above the draft diverter, heat can spill

out of the draft diverter into the adjoining space rather than exit through

the chimney. In addition, a vent damper lessens the amount of warm house

air that spills out the chimney. There are three types of vent dampers:

thermal, electrical and mechanical. Thermal dampers require no electricity

to open and close but depend on the expansion of heated metals (figure 8).

Electric dampers (figure 9) use either electric motors or solenoids to open

and close dampers. Mechanical dampers usually open when gas pressure is

high enough and close when pressure drops; they are not commerciajJy

available at present. Thermal dampers are the only practical dampers to

use in water heaters because they are not wired for electrical dampers.

Vent dampers, except for thermal dampers [253 cannot save any energy during

the on cycle. Even during the off cycle, they do not all close completely

[63

Energy savings depend on thermal communication between the area

surrounding the heat exchanger and the rest of the house. If there is

little communication, heat spilling out the draft hood or draft diverter

into the surrounding area serves no useful purpose.

If common vents serve two or more appliances such as the water heater and

furnace or boiler, a separate vent damper must be installed in each vent

connector in order to maximize energy savings (figure 8). If dampers are

19
not installed for each appliance, there will be increased draft in those

connectors without vent dampers (figure 8). This is illustrated by a laboratory study performed by the National Bureau of Standards [263.

Compared to not using any vent dampers at all, energy savings at the water

heater of 28.9 MJ/day (27,400 Btu/day) were measured when both a furnace

and water heater were equipped with vent dampers, while an extra 39.8

MJ/day (37,700 Btu/day) were lost by the water heater when only the furnace

was so equipped. Some electric dampers may require the installation of an

additional safety shut-off gas valve. Manufacturers' installation

instructions should specify if this is necessary.

4.4.1. Gas-fueled heating systems

With total communication between the area containing a gas heating system

and the remainder of the house, gas savings up to 15% are possible. Homes

with heaters located in unheated basements are expected to conserve little

gas even if there is communication between the basement and the rest of the

house [131. Overall savings in 146 houses with vent dampers were 5.1%

(table 2) [12].

4.4.2. Oil-fueled heating systems

Katzman and Monat [25] installed motorized flue danpers in 21 houses heated

by oil and obtained seasonal fuel savings of 6.5%. They estimated savings

by a National Bureau of Standards calculation procedure [27] to be 8.2% for

the average U. S. climate assuming that all units were 70% oversized [25],

Two different types of dampers were used, as were two types of burners:

conventional and flame retention head. Fuel savings differed by 1% or less

among these. Savings were highest for steam boilers, lower for hot water

boilers, and least for warm air furnaces.

Hoppe and Graves [21] measured savings of 9% in oil-fueled boilers using

electromechanical vent danpers. Hie installed cost in 1981 was $295. Vent

dampers save no additional energy when installed on optimized flame

retention head burners.

4.5. Reduced, excess dilution air

4.5.1. Resized vent connector

Reduced excess dilution air through the draft control device can be

achieved in gas-fueled equipment by reducing the cross-sectional area of

the vent connector (figure 5). In many homes retrofitted to reduce heat

loss or with thermostat setback, the furnace may either be replaced with a smaller unit or the input rate reduced to better match the new heating

requirements (as described under Derating) . Consequently, the venting

system will be oversized. It may have been oversized with the original

furnace as well. This results in excessive stack draft. The consequent

flow rate of heated room air out the stack is considerably greater than

needed for flue gas dilution. This is particularly true for older homes

with masonry chiimeys which are generally larger in cross-sectional area

than factory-built chimneys. This condition can also be corrected by using

a small section of pipe in the vent connector with reduced cross-sectional

area, without replacing the entire vent connector pipe. It is important

that whatever method is used, the vent pipe be visible for internal

20
inspection. Energy savings of 3.7% have been reported for vent resizing in

gas-fueled heating systems [12],

4.5.2. Forced exhaust

An alternative to rebuilding a masonry chimney or replacing a factory built

chimney when a chimney needs extensive repairs is direct side-wall venting

by a mechanical exhaust fan or power vent through the nearest outside wall,

as is done with clothes dryers. Side-wall venting is commercially

available and is most applicable to products that have electrical hook up.

Power venting can be adapted to gas-fueled water heaters even though they

do not have electrical hook up, by installing a commercially available

isolated electrical junction box [28] . The advantage of power venting over

natural draft is reduced off-period loss. The vent is practically closed

during burner off periods.

4.6. Flue gas heat reclaimers

Flue gas heat reclaimers are devices that capture heat that would normally

be exhausted out the flue (figures 10 and 11). An additional heat

exchanger can be attached to the flue to reclaim seme of the heat exiting

from the furnace or boiler heat exchanger. This heat can be used directly

for space heating, or for preheating water or return air [25], Flue gas

heat reclaimers used together with derating may cause condensation.

Whether condensation occurs or not is unimportant for water-spray type heat

exchangers (see below).

Katzman and Monat [25] obtained oil savings of 6.6% with four flue-gas heat

reclaimer devices in houses using oil-fueled burners. Three of the devices

were commercial "heat pipes", and one a homemade air-to-air heat exchanger.

(Energy savings were not directly measured but were determined by a simulation model.) The homemade unit yielded the greatest fuel savings,

10.5%. The authors claim that savings could have been doubled if the the

fan had been set to operate until outlet temperature reached 33°c (91°F)

instead of 57°C (135°F). The potential for energy savings with flue gas

heat recovery seems to increase with increasing flue gas temperature. That

is, there is greater room for improvement in efficiency the more

inefficient combustion is to begin with. For example, fuel savings were

6. 5-6.7% for two houses with steady-state flue temperatures of 327°C and

393°C, while a savings were 2.7% in one house with flue temperature of

235°C.

It is important to note that little or no energy will be saved unless heat

extracted from flue gas can be directed to areas of the house where heat is

needed. Simply blowing hot air into an basement unused as a living area

would not use all the recovered heat. Similarly, using recovered heat to

heat an unheated crawl space or attic would totally waste the recovered

heat

Hoppe and Graves [21] found oil savings of 10% in oil-fueled boilers using

flue gas heat reclaimers (see "Retention bead burners" above). The

installed cost in 1981 was $520.

The Alliance to Save Energy [22] claims that a secondary condensing waterspray type heat exchanger (figure 11) costs $600 to install on any fuel21
burning furnace and can save 25% of fuel use. Water is sprayed into the

flue gases to recover heat. The water is then pumped to a fin-tube heat

exchanger in the return air plenum, where it preheats air. The flue gas

temperature is reduced to about 40°C (100°F) and can be safely vented

through plastic pipe. Information on actual savings obtained in field

tests are not reported.

4.7. Thermostat controls

4.7.1. Automatic boiler water temperature reset control

Automatic boiler temperature reset control allows for using a boiler water

temperature which matches the amount of heat needed to maintain comfortable

room temperature for a given outdoor air temperature. This controller

automatically raises the circulating boiler water temperature setpoint as outdoor temperature drops, and reduces it in milder weather. Energy is

saved due to reduced energy stored in the boiler, therefore less heat is

lost out the stack during the off cycle. (This is particularly important

in the absence of a stack damper.) Energy savings of approximately 10%

have been reported. No additional energy was saved when installed on

optimized flame retention head oil burners [211.

4.7.2. Setback room temperature thermostats

Setback room temperature thermostats allow different temperatures to be set

for different times of the day or night.

Hoppe and Graves [21] found savings of 9% in oil-fueled boilers in houses

using dual setback thermostats (see "Retention head burners" above).

Houses were unoccupied during work hours. The installed cost was $80 for a one-zone house and $155 for a two-zone house. In combination with

automatic boiler water temperature reset controls, savings were 18% at an

installed cost of $390 to $425, depending on the number of zones (table 3).

Single night setback of 3°C (5°F) is reported to save 7% of the gas used to

heat a home [29]

U-«3._ Fan delay blower temperature control

Fan delay blower temperature control adjustment both after burner turn-on

and shut-down can be optimized, without compromising comfort, to recover

heat that would otherwise be lost out the stack. Gas savings of 6800 MJ/yr

(64 therms/year) has been reported. Electricity use has been reported to

typically increase by 610 MJ/year (170 kWh/year) since the blower motor

must operate longer. However, with utility rates of $0.0066/MJ

($0.70/therm) for gas and $0,017 ($0.06/kWh) for electricity, savings

amount to $35/year without need for any equipment, and minimal labor cost.

(Hie adjustment can be accomplished on some units with a screwdriver, and

on most units by moving a manual control dial.) Delay times corresponding

to these savings were 40 seconds after burner startup, and 160 seconds

after burner shutdown, or approximately 45°C (110°F) and 30°C (90°F),

respectively, for the warm air supply.

22
4.7.4. Thermostatic radiator valves

A thermostatic radiator valve automatically controls the flow of steam or hot water to a radiator in response to a remote thermometer. This permits

temperature control for individual rooms. Honeywell [30] claimed energy

savings up to 35%, without reporting either field tests or laboratory

simulation studies to substantiate any savings. Savings would undoubtedly

vary with setback patterns.

4.8. Replacement furnaces and boilers

4Al^. Fpcced-^lr furnaces

As mentioned previously, it may be more cost-effective to replace than to

retrofit an old furnace or boiler. New equipment offers many more years of

life at considerably higher efficiency than retrofitting. New forced-air

gas furnaces with annual fuel utiliaztion efficiency (AFUE) in the mideighty percent range are advertized at prices below $1000, with average

installed costs of $1300 to $1600 [311. (See "A directory of certified

furnace and boiler efficiency ratings" [323. This directory is an annual

publication which lists gas- and oil-fueled furnace and boiler AFUE by

manufacturer and model number, and fuel input and heating capacityJ Highefficiency condensing forced-air furnaces with AFUE in the low to midninety percent range would cost more than the Department of Energy limit of

$1600 [3] for single-family home. Average installed cost for oil forcedair furnaces, whose AFUE is usually in the high seventy to low eighty

percent range would be $1800 to $2000 [313.

4.8.2. Hot-water boilers

Prior to the introduction of high efficiency boilers in the late 1970's,

average boiler efficiency was 45-55% [333. Currently 80-85% AFUE is common. Average installed cost is $2500 to $2800 for a gas-fueled boiler

with AFUE up to 87%. An oil-fueled boiler with 80-83% AFUE is reported to

have an average installed cost of $1900-2200.

4.8.3. Determining energy savings from annual efficiency ratings of furnaces

and boilers

A simplified calculation of energy savings can be done as follows. For

each unit of energy supplied to the home, the energy into the furnace or

boiler is 100%/AFUE.

% energy savings = 100 x <100/AFUEold furnace _ i00/AFUEnew furnace)

The AFUE of the old furnace is unknown but it can be estimated by testing

combustion efficiency during continuous burner operation (i. e. steadystate efficiency). This should be done during normal maintenance and

servicing of the unit.

AFUE may be estimated as steady-state efficiency less 10% for a gas

furnace. This is based on a reference system with the difference between a steady-state efficiency of 75% and a part-load average seasonal system

efficiency of 66% [293. Another source [343 considers a reference gas

furnace seasonal efficiency to be 60%. In general, a 15% difference would

23
be the more appropriate difference between these two efficiencies for older

units in the field. For gas-fueled furnaces and boilers, the lower the

initial system efficiency, the greater the potential energy savings. For

example, improving system efficiency from 50% to 60% saves 20% of the

energy, while improving it from 70% to 80% saves 14%, as discussed in

section 4.1. Savings beyond the efficiency improvement can result from

proper sizing. Oak Ridge National Laboratory [9] estimates that gas-fueled

furnaces oversized by a factor of two require 8-10% more gas than properly

sized furnaces. This calculation of energy savings does not take into

account the electric energy used for the blower or other electric powered

devices. (This amounts to perhaps an additional 5% of the annual cost of

operation. However, its effect cancels out in comparison if one assumes

that both old and new equipment use about the same amount of electricity.)

A more detailed calculation of annual cost of operation based on

geographical location, and a given design heating requirement is given in

"A directory of certified furnace and boiler efficiency ratings" [321.

4.9. Electronic pilot ignition devices

Intermittent ignition devices ignite gas to begin the combustion on cycle,

eliminating the need for a constantly burning pilot light.

Most older gas furnaces and boilers have a pilot burner in addition to the

main burner. The pilot burner may be on all year, consuming fuel at a rate

of about 300 W (1 cfh or 1000 Btu/h) [9]. The pilot burner supplies useful

heat during winter but wastes fuel (about 5-10% of total annual consumption

[9]) during the summer if it is not turned off (figure 4). In addition, it

may impose an additional heating load on the air conditioner during summer.

The pilot burner ignites fuel at the main burner at the start of the on

cycle. Intermittent ignition devices either replace pilot lights (direct

spark ignition systems) or turn them on (pilot ignition systems) when there

is a call for heat. Direct spark ignition systems are available only in

new appliances, not as retrofits.

Most intermittent ignition devices, in conjunction with flame sensing

devices (thermocouples, diastats or bimetals), also serve the additional

safety function of shutting off the supply of gas to the main burners if

ignition does not take place. Intermittent ignition devices operate much

as spark plugs; a high voltage spark ignites fuel. When ignition is

proven, a flame sensing element signals a control module, which stops

sparking. Most intermittent ignition devices used for retrofits use an

electronic flame ionization sensor to test for a flame [61. If the flame

is extinguished, the entire system is shut down. In the SHEIP study, gas

savings in 24 houses using intermittent ignition devices were 4.4% (table

2 ) [ 12 ].

Energy savings depend on pilot size, total annual fuel use, and length of

heating season. For example, for a typical pilot burner burning gas at the

rate of 440 W (1500 Btu/h), fuel waste during a 5-month non-heating season

(May-Septemper) would be 5700 MJ (54 therms) for a cost of $32/year at

$0.0056/MJ ($0.60/therm) . For a typical central heating system using

107,000 MJ/year (1000 therms/year), this would be an energy savings of

5.4%.

i

24
Retrofit of intermittent ignition devices is questionable. Energy savings

may not justify expected installed cost of about $200 [35], If the pilot

is turned off during the non-heating season, intermittent ignition devices

would save no additional fuel at all.

4.10. Insulating exposed duct.i&ik

Insulation of exposed ducts in unheated areas can reduce heat loss. Figure

4 shows the heat losses for a gas furnace system [91. Uninsulated ducts

passing through unheated crawl or attic spaces can lose heat at the rate of

about 2.6 W/nr ,0C (1.5 Btu/h*ft2,0F) . This can amount to 40% of the heat

output of a furnace [9]

,

and may be the largest single source of waste in

the heating system.

ANSI/ASHRAE Standard 90A [363 includes a section on minimum air-handling

duct system insulation. This standard is based on the design tenperature

differential ( T) between the ambient air temperature and the duct surface.

The required R-factor is R - T/15 ft2oh*F/Btu.

Also see the NBS report "Recommended criteria for materials and products to

be included in the DoE weatherization assistance program" [373.

4.11 . Zope. cQptjol

4.11.1. Radiator and warm air register covers

The Institute for Human Development [383 developed aluminized mylar, and

more recently, aluminized fiberglass, radiator covers that can be used to

selectively control radiators in a house, for example in unoccupied areas. For hot air systems, plastic cut to the size of air registers serves the

same purpose. Water pipes located near heating pipes or ducts will not

freeze if these retrofits are used. By contrast, it is difficult to

selectively heat parts of heating zones with many modern systems, and if

they were turned off in sane zones, nearby water pipes might freeze.

To date, 193 of these retrofits have been installed in Philadelphia and its

suburbs, and 20 in Minneapolis-St. Paul. The installed cost is less than

$600, and preliminary results indicate that up to 40% reduction in fuel use

can be achieved.

4.11.2. Thermostatic radiator valves (see 4.7 .4

J

5.Q. .. Water Jaea^ing_r_etj^^ The typical energy consumption of a residential electric or gas water

heater is about 22,000-30,000 MJ/yr (6000-7500 kWh/yr or 21,000-28,000

Btu/yr) [39, 403. Thermal losses account for 30% of electric water heater

energy losses, and 50% of gas- and oil-fired water heater energy losses

[41, 423 . Standby losses are estimated to be 3200-4300 MJ/yr (900-1200

kWh/yr), or 15-20% of total energy consumption for standard residential

water heaters, and 2950-3310 MJ/yr (820-920 kWh/yr), or 14-15%, for some

commercially available energy saving water heaters [391

The National

Bureau of Standards [433 tested water heater energy conservation measures

in nine water heaters for their ability to reduce these losses. The

25
measures tested were 1) reduced thermostat settings, 2) increased

insulation, 3) intermittent ignition for gas-fired heaters, and 4) flue

dampers for gas- and oil-fired heaters. The reported results are

applicable to most, if not all, types of residential water heaters because

most of these differ mainly only in heat source and storage volume [41],

Energy savings for combinations of these retrofit measures are shown in

table 4.

In a computer simulation study, Oak Ridge National Laboratory [42]

predicted energy savings due to various conservation measures for gas and

electric water heaters. Table 5 lists energy savings and cost increases of

various combinations of these measures. Using a combination of

conservation measures that would raise the initial cost of a water heater

by 26 or 27%, electricity consumption could be reduced about 17%, gas

consumption could be reduced about 27% [421. The conservation measures

include increasing thickness and reducing thermal conductivity of jacket

insulation, reducing thermostat setting, and adding insulation to the

distribution pipe.

Below, individual energy conservation measures suitable for retrofit are

described and their energy savings estimated.

5.1.. Reduced excess dilution air

Reduced excess dilution air can result from reduced size of new water

heater. See section 4.5.1 for a discussion of reducing excess dilution air

by resizing the vent connector.

5.2. Reduced thermostat settings

Energy can be saved by reducing the water heater thermostat setting during

normal operation, and by reducing the thermostat or turning off the heater

altogether when the house is unoccupied. Since most thermostats are

adjustable, this can be done by the owner. Lowering the thermostat can

only be done if there is enough water available. This measure is more

valid with gas than with electric water heaters because temperature

recovery takes about twice as long in electric heaters. Lowering the

thermostat reduces energy demand because less energy is required to heat a given volume of water, and because heat losses from the tank jacket, flue,

exposed fittings and service connections are reduced. In homes without

dishwashers or with dishwashers with inline water heaters, thermostats may

be set as low as 50°C (122°F) [43]. Most dishwasher manufacturers

recommend temperatures in the range 60-70°C (140-160°F).

Energy savings were about 12% for a thermostat setback of 10°C (18°F) , from

70°C (158°F) to 60°C (140°F) , in heaters with no extra insulation [43]. In

another study of two electric heaters, (190 kWh/yr) was saved by reducing

the thermostat setting 11.2°C (20°F) , from 65°C (150°F) to 55°C (130°F)

[44], Savings were 9% for heaters with extra insulation [43]. ORNL [42]

calculated energy savings of 5% for a thermostat setback of 5.6°C (10°F) on

gas-fired and electric water heaters (table 5). There is no equipment cost

increase [42],

26'
5.3.

Add-on tank insulation

Jacket losses are a major source of heat loss in water heaters. An

insulated blanket may substantially reduce jacket losses [43],

Increasing the thickness of fiberglass insulation from 50 mm (2 in) to 75

mm (3 inches) saved 470-720 MJ/yr (130-200 kWh/yr) depending on tank size

[441.

Extra insulation saved 7-9% of the energy used to heat water in standard

heaters. Only 2.6% of the energy was saved in an energy-saving electric

water heater that was originally insulated better than standard heaters.

In the ORNL simulation [42] increasing jacket insulation from 5.1 cm (2

inches) to between 7.6 cm (3 inches) and 12.7 cm (5 inches) fiberglass

insulation saved 4-7% of the energy needed for an electric water heater at

an initial equipment cost increase of 4-12%. Increasing insulation from

2.5 cm (1 inch) to between 5.1 (2 inches) and 12.7 cm (5 inches) saved 7-

11% for a gas-fired heater at an initial cost increase of 3-14% (table 5).

NBS Special Publication 606 [7] includes "Standard practice for the

installation of thermal insulation in domestic water heaters."

5.4. Insulation of distribution, pipe ORNL [42] estimates that gas water heaters lose 3%, and electric heaters

5%, of their energy through the first 7.6 m (25 ft) of distribution pipe.

ORNL estimates that 3% of the energy used to heat water can be saved by

insulating this pipe, at an initial cost increase of 9-10% (table 5).

Ontario Hydro [39] estimate that insulating short lengths of distribution

pipe, 1.5-2.6 m (4. 9-8. 4 ft), above the tank, saved 270 MJ/yr (75 kWh/yr).

The National Bureau of Standards [45] estimates that insulating pipes

leaving water heaters can save energy at the rate of 4 W, or 125 MJ/yr (35

kWh/yr) .

According to ANSI/ASHRAE Standard 90A [36] , service water heating pipes up

to 2.5 cm (1 inch) in thickness should be insulated with 1.25 cm (0.5 inch)

of insulation.

5.5. Heat traps

Heat traps are curved sections of pipe, or check valves, that brake the

natural tendency of heat to rise out of a water heater by both convection

and conduction. Several types of heat traps are shown in figure 12 [461.

Ontario Hydro [39] measured energy savings on an energy efficient water

heater. They estimate that commercially available copper heat traps can save 125 MJ/yr (35 kWh/yr) , vtfiile experimental plastic heat traps can save

about 360 MJ/yr (100 kWh/yr). Insulating short lengths of distribution

pipe, 1.5-2.6 m (4.9-8. 4 ft), above the tank, saved 270 MJ/yr (75 kWh/yr),

while in combination with plastic heat traps, savings were 595 MJ/yr (165

kWh/yr). The National Bureau of Standards [46] estimates that for water

50°C (90°F) warmer than room terperature, insulating pipes leaving water

heaters can save energy at the rate of 4 W, or 125 MJ/yr (35 kWh/yr); heat

traps can save energy at a rate of 8 W or 250 MJ/yr (70 kWh/yr). These

results indicate that far less energy can be saved when pipes are

horizontal rather than vertical. This is because energy loss from

27
horizontal pipes is already lower than from vertical pipes. Horizontal

pipe is an inherent heat trap. Its geometry discourages thermal convective

flow.

-Venfc-dglIE>££g.

A vent damper installed on the water heater vent pipe acts to reduce the

amount of heated room air lost out the stack more than it helps to reduce

energy consumption by the water heater. Therefore, the use of a vent

damper should only be considered where heat recovered at the water heater

vent can be useful to heat the home. When the water heater is installed in

unheated areas, there is little advantage to installing a vent damper. Cne

type of damper that closes off both the flue and stack had been approved

for manufacture but is presently not in production. That type is referred

to as a mechanical damper. The most common type of vent damper applicable

to gas fueled water heaters is the thermal damper, because water heaters do

not have electric hook-up and thermal dampers do not require it. See

figure 9 (a)

A rule of thumb is that if a vent damper has been installed at the furnace

or boiler and if the heating system is installed in the same area as the

water heater then the water heater vent should also be equipped with a vent

damper.

See section 4.4 for additional discussion of vent dampers.

5-*?-.. Combination Boiler/Water Heater (Tankless Coil System)

One type of water heating system which has not been included in figure 2 is

the combination boiler/water heater; also referred to as the tankless coil

type boiler. This system uses a heating coil immersed in the boiler to

supply hot water on demand for showers, bathing, clothes washing etc. This

type of water heater is very efficient during the winter months when space

heating is also needed. However, during the non-heating season this system

uses an inordinate amount of energy compared to storage tank water heaters.

A new tankless coil system would be allowed, under ASHRAE Standard 90, a stand-by loss of roughly 3300 BTU/hr. (calculated based on typical assigned

values for a family of 4) vs. 1500 BTU/hr. for a gas or oil fueled tank

type, and 400 BTU/hr. for an electric tank type. During the non-heating

season it would likely be more cost effective to install a tank type water

heater and shut the boiler off. (See Figure 6.) Another advantage to

using a separate storage tank has been reported in (47) which involved a field study of residential oil fired heating systems in New England. In

that field study, it is reported "Reserve storage tanks were installed to

satisfy the demand for hot water while the firing rate of the system was

reduced to more nearly match the heating load of the residence." This

resulted in an average space heating fuel savings of 13%. (See section

4.1.2.) If the add on tank were being considered for the benefits derived

from derating the heating system, it would be possible to gain the

additional benefit of a more efficient water heating system as well. An

electric water heater tank could serve as the add-on tank during the

heating season with the electric resistance heater turned off and using the

boiler to heat water. During the non-heating season, the electric water

heater would operate normally (with the resistance elements), with the

boiler shut off. The cost effectiveness of this option would need to be

28
investigated since it would be controlled by the local utility rates, and

the length of the non-heating season, and fuel used with the tank type

heater

6.0. Heat pump. water heaters

Heat pump water heaters operate on a vapor-compression cycle similar to

that of a window air conditioner. Heat is pumped from the air in the room

surrounding the device into the water tank. Figure 13 shows an integral

heat pump water heater and figure 14 shows an add-on heat pump water

heater. Oak Ridge National Laboratory [483 tested 85 integral heat punp

water heaters in homes. They estimated that heat pump water heaters use

12,020 MJ/yr (3339 kWh/yr) , compared to 22,520 MJ/yr (6256 kWh/yr) for an

electric resistance water heater, saving 47%, or 10,500 MJ/yr (2917

kWh/yr). This amounts to $X45/year assuming an electricity cost of

$0.18/MJ ($0.0 5/kWh) . Oak Ridge estimates that heat pump water heater

initially costs $600 more than a resistance water heater. Heat punp water

heaters operated at an average cop of 1.9. There was no correlation

between cop and regional climate. Cooler air temperature and noise were

not a problem if the water heater were not too close to the living area.

7.0. Heat recovery from central air conditioners by desuperheatexa

Heat recovery units that use waste heat from air-to-air heat pumps and

central air conditioning systems to heat water are commercially available

(figure 15). Heat from superheated refrigerant is transfered to water in a heat exchanger, and the heated water is stored in the hot water tank. Heat

exchangers that can be used for retrofitting existing systems are

available, as are complete systems for new installations [493.

Cooling performance is typically slightly improved. Heating output of a

heat pump during the heating season is reduced approximately 20%, which

means that the heat pump must run approximately 25% longer to satisfy the

thermostat. In colder climates, the reduced heating capacity could result

in cold supply air complaints, and longer defrost cycles. Therefore, it is

common to open the electrical circuit to the hot water circulating pump

with an outdoor thermostat set to open at 1.5-4.5°C (35-40°F) [501

Several heat recovery units were tested by the National Bureau of Standards

[49, 513 Some of the major conclusions are: 1) air-to-air heat pump

performance is improved because of the decreased power required for the

compressor? 2) hot water requirements cannot be met during the heating

season by heat recovery alone? 3) there is little or no increase in

operating costs? 4) heat recovery is most effective in areas, such as the

southern United States, where air conditioning requirements are high.

Energy savings are estimated to occur at rates of 90-135 W (800-1200

kwh/year) for four cities in different parts of the United States. This

amounts to $ 40-60/year assuming electricity costs of $0.014/MJ ($0.0 5/kWh)

[493 .

Oak Ridge National Laboratory [523 compared energy use of desuperheaters

(heat recovery units that use waste heat from air-to-air heat pumps or air

conditioners) and electric resistance heaters in 115 United States cities.

They found that during desuperheater use, consumption of electricity was only about 5% of the heat added to the water heater. The average homeowner

29
could expect to save in southern areas, about 66% of the electricity used

for domestic hot water, and in northern areas, about 23% of the

electricity*

The Florida Public Service Commission [53] sponsored a comparison study of

76 standard electric resistance water heaters, energy conserv-?rr

resistance water heaters insulated according to ANSI/ASHRAE Stanaara 9ua

[ 36] (called "conventional" in the Florida Public Service Commission

report) , desuperheater water heaters, integral and retrofit heat punp water

heaters, and solar hot water heaters in four different areas of Florida.

Monthly coefficient of performance is shown in figure 16. It is clear that

waste heat recovery and heat pump water heaters, in that order, have by far

the highest coefficients of performance during the cooling season. Energy

and dollar savings, and calculated return on investment are presented in

table 6 (the average electricity cost is about $0.02/MJ ($0.07/kWh))

Energy and dollar savings, and costs, in decreasing order, were solar hot

water heaters, heat pumps, desuperheaters, and conventional electric

resistance heaters. Heat pump water heaters were found to be unreliable

because of frequent compressor failure. The high coefficients of

performance of waste heat recovery during the cooling season are so

advantageous to utilities in reducing peak loading, however, that the

authors suggest that utilites subsidize homeowners to install these

devices.

Life-cycle costs of desuperheaters, heat pump water heaters and

conventional gas-fired water heaters were compared for Minneapolis,

Knoxville, and Tanpa [52, 54], Present value life-cycle costs were lowest

for gas heaters in all cities ($1041-1443). Heat pump and desuperheater

water heaters used about the same amount of electricity, and cost

approximately the same over their lives ($1289-2749). It should be borne

in mind that these costs were computed in 1979; the price assumed for gas

was $0.00367/MJ ($0.387/therm or $3.87/mcf) , and for electricity $0.0083-

0. 014/MJ ($0. 03-0. 05/kWh) . (The highest electricity price was in

Minneapolis.) As of June, 1983, gas cost $0.00623/MJ ($0.657/therm or

$6.57/mcf) in Minneapolis, an increase of 70%, while electricity cost

$0.019/MJ ($0.068/kWh) , an increase of 14% [55] . Therefore gas lost some,

if not all, of its relative cost attractiveness compared to electricity

since the ORNL report. (If gas-fired water heaters operate at an

efficiency of 50%, and electric water heaters at 75-80%, then in

Minneapolis, electric air-to-water heat pumps would be more economical if

their cop was above about 2, considering only energy costsJ

Arthur D. Little, Inc. [56] calculated that the payback period is two years

for new factory installed units that recover heat from air-to-air heat

pumps, three years for units that recover heat from air conditioners, and

twice as long for retrofit devices. They assumed that in 1979 retrofit

units cost $500 installed, factory installed units cost $250, and heat

recovery rates are 17% of cooling rate and 0.08% of heating rate.

Projected ejectricity savings range from a rate of about 120 W (1050

kVJh/year) in the Pacific and New England states to 285 W (2500 kWh/year) in

the West South Central states.

30
8.0. Maintenance

8.1 . Central Air Conditioners

The Trane Company performed a study on an eight year old residential air

conditioning unit [57] . The objective was to "determine the impact of wear

and tear on the operating efficiency and cooling capacity of the old air

conditioner that has received maintenance similar to many units presently

owned and operated by homeowners." Their findings showed that a twenty

percent improvement in efficiency could be achieved by a tune up. This

included cleaning the coils (evaporator and condenser) and adjusting to the

proper refrigerant charge. After replacing the coils and installing a new

compressor, efficiency increased another twenty percent, mostly due to the

compressor. Trane found that a ten percent drop in refrigerant charge

caused efficiency to drop off by twenty percent.

The importance of proper refrigerant charge has been investigated in detail

by the Texas Power and Light Company (Ref. [58]) in a labortory test of a

1.5 ton split system unit. The following is from their report: "Inproper

charging can best be defined as either a refrigerant overcharge or

undercharge when compared with the manufacturer's charging specifications,

at standard API rating conditions. Either condition will have a detrimental effect on the system, both in terms of equipment life

expectancy as well as operating efficiency and economy.

"An undercharged condition will create abnormally high superheat which has

an adverse effect on compressor motor winding cooling. The long term

effect will be the eventual breakdown of motor winding insulation with

premature compressor failure as a result. In extreme cases, due to the

repeated opening of the internal motor overload protector, a much faster

failure could occur.

From the operational standpoint, it is calculated that a refrigerant

undercharge will cause the system capacity to decrease corresponding to the

amount of undercharge. This is caused by a loss of refrigerating effect

due to increased superheating of the refrigerant vapor."

Figure 17, entitled "Effect of Refrigerant Overcharge or Undercharge on

System Performance Compared with Proper Charge," conpares the effects, on

system capacity and demand (kW) , of a 23% refrigerant overcharge against

proper charge.

"As illustrated by the curves in Figure 17, the undercharge condition

affects the system operating efficiency and operating cost by causing a rapid decline in total capacity as the outdoor ambient increases, while at

the same time the electrical demand (kW) is increasing at a slower rate.

The resultant drop-off in system efficiency (EER) is very pronounced. The

23% by weight undercharge changed the EER from 8.31 to 5.49 at 95°F. This

is a 52% increase in operating cost. As a result, for this 1 1/2 ton unit,

the annual operating cost can be expected to be increased by (1.23 kW x 1700 Hrs x $.07) = $133.63. In addition, the long term effect of elevated

suction gas temperatures caused by this undercharged condition will reduce

the life expectancy of the compressor. Some manufacturers claim this to be

as much as 50%.

31
"The results of overcharge on system performance, as shown by the curves,

is a slight increase in capacity over the proper charge but at a higher

cost in terms of electrical demand (kW). As the outdoor ambient increases,

the capacity and demand both approach an intersecting point with the proper

charge curve."

"A refrigerant overcharge can reduce the life expectancy of a compressor

due to the effects of liquid floodback, slugging, and motor overheating

caused by abnormal head pressure and/or compression ratios."

8.2. Heating Systems

8.2.1. Oil Fueled Furnaces and Boilers

The subject of maintenance is most important for the oil fueled heating

equipment because of the potential for efficiency degradation with poor

combustion due to soot accumulation on the heat exchanger accompanied by

reduced beat transfer and high flue gas temperatures. These effects are

shown graphically in Bachrach Bulletin No. 4011 on Oil Burner Combustion

Testing [59]. Field test results reported there show that initial smoke

numbers greater than two (Bachrach scale) result in eventual rapid drop off

in efficiency. An example of one test unit is given where an initial smoke

reading of No. 5 resulted in an efficiency drop from 72% to 66% after one

thousand hours of burner operation. That efficiency degradation would mean

that 9% more fuel would be required at the start of the second year of

operation if the furnace heat exchanger had not been cleaned. Causes of

the problem are related to improper draft, improper adjustment of

combustion air, poor mixture of fuel and air and improper combustion

chamber size for the burner flame. A section titled "An understanding of

oil fired heating systems" should be referred to in (Ref. [201). Also

included in that reference are "Equipment Installation and Adjustment

Procedures" and "Heat Losses and Modifications to Improve Efficiency."

Che consequence of poor maintenance described in detail in Ref. [20] is the

possible need to replace turbulators (baffles) in steel tube boilers.

Frequently, turbulators need replacement because of partial destruction

after many years of service, or removal during previous boiler cleaning

without replacement.

Turbulators reduce flue gas temperature and reduce heat loss. It is

important to be sure there is adequate chimmey draft before installing

turbulators. The savings potential of a turbulator is listed in that

reference as 5 percent, and the savings potential of a tune-up for systems

that are regularly adjusted is about 3 percent.

NBS publication [7] includes a section on "Tune-up and Evaluation of

Existing Burner." See Table 7 for details of the annual dollar saving to

be expected by increasing steady state efficiency. The Bachrach Instrument

Company [59] describes burner service and proper combustion test

procedures

32
8.2.2. Gas Fueled Furnaces and Boilers

Routine maintenance should include replacing filters, removing any scale

that may have dropped onto the burners, cleaning dust, lint, etc. from the

blower housing and motor, and lubrication of fans or other motors and puirps

that require it (other than oilless bearing type)

Combustion checking of the unit with adjustment of the primary air supply

to the burner is recommended. This should include checking the carbon

monoxide to insure that it is not increased above the accepted level (not

greater than 400 ppm air free is required for ANSI approval of furnaces and

boilers). Many potentially hazardous situations can be found and corrected

during a tune-up of the furnace. One of these is the possibility of a

corroded heat exchanger that has developed a hole. Several methods of

detecting a leaking heat exchanger are described in "Field Service and

Adjustment of Gas Space Heating Equipment" [61. These methods include

comparison of the flame appearance with the blower off versus blower

operating, smoke tests, salt tests, and odor tests. However, that

reference states "the only reliable method that ensures that a heat

exchanger is not leaking is a visual inspection of the exchanger." This

requires dismanteling the appliance and is therefore time consuming.

Field tests by seven gas utility companies have confirmed the superiority

of a new method to detect leakage through furnace heat exchangers [60].

The method involves the injecting a special tracer gas mixture at the

burner side of the heat exchanger and measuring for leakage on the air side

using a calibrated detecting meter. Since major retrofitting is also

costly, it is strongly recommended that if a furnace heat exchanger is

older than 10-15 years that an inspection or testing be made before

expending the money and effort to do a major retrofit of the unit. A major

retrofit is considered to be derating, or installation of a heat extractor;

electric ignition and vent damper.

The most significant common problem reported [63 for hydronic heating is

scale formation in the steam and condensate water passageways. These

deposits can obstruct water flow and decrease heat transfer. See (Ref.

[63) for further details of the fundamentals involved in field service and

adjustment of gas heating equipment. The Bachrach Company's "Gas Burner

and Combustion Testing" Bulletin 4006 outlines the fundamentals of gas

burner combustion and reviews testing and tune-up techniques (Ref. [611).

8.3. Water Heaters

Degradation of energy efficiency over time in gas fueled water heaters is

due mainly to insulating layers of scale on the tank bottom and walls,

burner malfunction or misadjustment, and degradation of the heat transfer.

This latter degradation can result from baffle deterioration, rust and soot

accumulation in the flue, and flue blockage [62]

NBS studied the mechanism of gas-fueled water heater degradation by

examining 26 used water heaters from different parts of the United States

[623. The operating life of water heaters is related to the total

dissolved solids content of the water supply and temperature (Refs.

[63] and [643).

The corrosion rate doubles for every 11°C (20°F) rise in

temperature. The principal cause of failure of gas-fueled water heaters is

33
corrosion induced leakage. Most water heaters are protected against

corrosion by a glass lining and a sacrificial magnesium anode, which is

preferentially attacked, protecting the tank. After the anode

disintegrates, however, there is no further protection.

Many of the helpful hints on saving energy state that in order to prevent

these deposits from building up that the homeowner should drain off water

from the tank periodically. However, that energy saving hint is not

effective in removing scale and deposits from the bottom of a tank because

the drain valve is always a few inches above the tank bottom. The only

effective way to remove these deposits is with a special chemical cleaning

solution. (66)

Combustion testing of fossil fueled water heaters is also reconmended. Hie

same combustion test methods and procedures described in references in

section 8.2 also apply to water heaters.

Also "Guidelines for Adjustment of Atmospheric Gas Burners for Residential

and Commercial Space Heating and Water Heating" [67] is a publication that

includes detailed adjustment procedures to minimize air pollution and to

achieve efficient use of gas.

34
9.0. Standards

The following standards are believed to be the most current, however these may

be revised following publication of this report. Some of the retrofit

procedures cited in this report are not covered specifically by installation

standards. In some instances, the referenced standard may or may not be in

conformance with local codes. Local code officials should be consulted.

9.1. Space Heating System Retrofit

Retrofit Product or Procedure Standards

1) Installation of Gas Conversion

Power Burners (for Gas or Oil

Fired Systems) In conformance with, or latest, ANSI

Z21.8a, ANSI Z21.17 and Installation

ANSI Z223.1 - 1980

AGA Laboratories Certification Seal

2) Replacement Oil Burner ANSI Z96.2 (UL 296)

ANSI Z91.2

NFPA 31-1983

3) Power Burners (Oil/Gas) Conformance to ANSI Z223.1, National

Fuel Gas Code; ANSI Z83.1 Gas

Installations; NFPA 31 Oil

Equipment

4) Furnaces, Oil Installation of Oil Burning Equipment,

NFPA 31-1976

5) Furnaces, Gas Gas Fired Central Furnaces, ANSI

Z21.47 - 1978

6) Boilers Boiler and Pressure Vessel Code

(eleven sections) ASME 1980 or latest Testing and Ratings

Hydronics Institute (HYDI)

7) Reduced Input of Burner, Derating

(a) Gas Fueled In conformance with Local Utility

Company Procedures if applicable for

gas fueled furnaces.

(b) Oil-Fired EPA 600/2-75-069-9 "Guidelines for

Residential Oil Burner Adjustments"

Conformance to NFPA 31-1983, Standard

for the Installation of Oil Burning

Equipment

35
8) Replacement Combustion Chamber,

in Oil-Fired Furnace, Boiler Conformance to NFPA 31-1983

9) Gas Fueled Heating Systems, Vent

Danpers Conformance with applicable sections,

National Fuel Gas Code including

Appendices H, I, J and K

ANSI Z21.66 - 1977 and Addenda A and

B for Electrically Operated Danpers

ANSI Z21.68 - 1978 and Appendices A

and B for Thermally Activated Vent

Danpers

ANSI Z21.67 - 1978 and Appendices A

and B for mechanically actuated vent

danpers

10) Oil Fueled Systems, Vent Danpers . .Conformance with applicable sections of

NFPA 31-1983 for installation and in

conformance with UL 17

Reduce Excess dilution air:

(a) Reduction of Vent Connector

Size of Gas Fueled

Appliances See Part 9 of ANSI Z223.1 - 1980 and

Appendix G and H

(b) Adjustment of Barometric

Draft Regulator Oil Fuels ... .NFPA 31-1980 for Oil Fueled and per

manufacturers' (furnace and burner)

instructions

11)

Replacement of constant burning

pilot with electric ignition

device on gas fueled furnaces

or boilers ANSI Z21 .7-1981

12) Duct Insulation See NBS Recommended Criteria (Ref. 7)

Pipe Insulation Table 3 for Thermal Insulating

Materials. Also see ASHRAE Standard

9QA-1980 Section 5 (Ref. 36)

13) Clock Thermostats. Conformance to NEMA

1

DC 3-1978 or NEMA

DC 15-1979 and performance test

requirements2

1 NEMA indicates National Electrical Manufacturers Association. , . , 2 The performance tests requirements are: u) tne operating differential

should not exceed 2of, and (2) the effective operating drop should not

exceed 4oF when determined according to the applicable procedures in

DC 3-1978 and DC 15-1979.

36
9.2 Water Heating

9.2*1. New. Presets

Retrofit Product or Procedure Standards

1) Heat Punp water Heaters ...Listed by Underwriters Laboratories

Standard for Electric Water

Heaters Under Development by ASHRAE

Efficiency Certification per Gas

Appliance Manufacturers Association

(GAMA) or Air Conditioning and

Refrigeration Institute (ARI)

2) Oil, Gas, and Electric water

Heaters . .Efficiency certification per GAMA.

ASHRAE Standard 90A-1980 for

guidelines on minimum performance

required for recovery efficiency

and standby loss

3) "Desuperheater/water Heaters" ...

...Conformance to ARI 470-80

Conformance to ARI 1060-80

9.2.2 Retrofits

Retrofit Product or Procedure Standards

1) Insulate Tank and Distributing

Piping , . .NBS Report on Criteria for Insulation,

also see ASHRAE 90A-1980 - Section 7

on Service Water Heating

2) Install Heat Traps on Inlet and

Outlet Piping . .Applicable local plumbing code

3) Install Stack Damper, Gas Fueled ... .ANSI Z21.68, 1978

ANSI Z21.67, including addendas A

and B

ANSI Z223.1 - 1980

4) Install Stack Damper, Oil Fueled ... .UL-17

NFPA 31-1983

37
REFERENCES

1. 10 CFR Part 440

2. 42 U.S.C 6861 et seq.

3. U. S. Department of Energy, "Weather ization assistance for low-income

persons," Federal Register 48, 51068-51083, 1983.

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measurement and characterization of residential heating equipment,

Brookhaven National Laboratory, report no. BNL-51242, Upton, NY, 1980.

5. D. W. Locklin, H. R. Hazard and L. W. Woodworth, "A review of

technology for the development of high-efficiency oil-fueled

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8. J. W. MacArthur and L. W. Nelson, "Hybrid simulation of a residential

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9. E. C. Hise and A. S. Holman, "Heat balance and efficiency measurements

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10. American Gas Association "Space Heating System Efficiency Program

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11. Consumers Union, "Consumer reports money saving guide to energy in the

home, revised edition," Mount Vernon, NY, 1982.

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correlation of seasonal performance data from the gas industry's Space

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American Gas Association, Institue of Gas Technology, Chicago, 1980.

13. T. S. Zawacki, J. T. Cole, V. Huang and R. A. Macriss, "Effect of

building structure and of space heating installation on furnace/boiler

retrofit effectiveness," ASHRAE Trans. 83(1B) 735-750, 1983.

14. D. J. Whitlock, "Gas furnace derating and corrosion," presented at

ASHRAE seminar, semiannual meeting, Atlanta, 1984.

38
15 . D. J. Whitlock, "A utility program for derating residential furnaces,"

pp. D-93-D-106 in "1978 operating section proceedings," American Gas

Association, Arlington, VA, 1978.

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seasonal efficiency," prepared for National Bureau of Standards,

Honeywell Corporate Research Center, Bloomington, MN, 1975.

17. G. E. Kelly, letter to D. Rosoff, Federal Energy Administration (now

U. S. Department of Energy), National Bureau of Standards, Washington,

December 23, 1975.

18. L. Katzman and D. Weitzman, "A study to evaluate the effects of

reducing firing rates on residential oil burner installations," W&lden

Research Division of Abcor, Inc., for National Bureau of Standards,

Washington, July 1976.

19. National Bureau of Standards and Federal Energy Administration (now U.

S. Department of Energy), "A service managers guide to saving energy

in residential oil burners," U. S. Department of Commerce report

number LC 1082, Washington, June 1977.

20. J. Batey and G. Butler, "A guide to efficient oil heating in homes,"

National Oil Jobbers Council and U. S. Department of Energy, report

number DOE/CS/23967-1 , Washington.

21. R. J. Hoppe and W. L. Graves, "Field tests of refit options for

residential oil-fired heating equipment," Brookhaven National

Laboratory, report no. BNL-51555, Upton, NY, 1982.

22. Alliance to Save Energy, personal communication, Washington.

23. U. S. Department of Energy, "Increasing benefits of energy assistance

programs through oil furnace retrofits," Washington, July 1981.

24. M. G. Finn and R. Garey, "The cost effects and extent of subgrantee

use of weatherization program regulation changes," Oak Ridge National

Laboratory, Final Working Paper, Oak Ridge, TN, 1981.

25. L. Katzman and J. Monat, "Study to evaluate the energy efficiency

improvement of residential heating equipment modifications," prepared

for National Bureau of Standards, Walden Division of Abcor, Inc.,

Wilmington, MA, 1978.

26. E. Kweller and R. Pal la, Jr., "Laboratory test results of energy

savings determined for thermally activated vent dampers installed with

a gas-fueled water heater," letter report prepared for the Department

of Energy, National Bureau of Standards, Washington, July 1981.

27. U. S. Department of Energy, "Weather ization assistance for low-income

persons; interim rule," Federal Register 45, 13028-13041, 1978.

Tjernlund Products Inc., "Side wall vent systems," (advertising

literature), St. Paul, 1982.

^ Q

28.
29. G. K. Gable and K. Koenig, ASHRAE Trans. 83(1) , 850-864, 1977.

30. Honeywell, advertising literature, 1979.

31. "High efficiency furnace review," Contracting Business 38, 49-53,

1983

.

32. "A directory of certified furnace and boiler efficiency ratings," Gas

appliance Manufacturers Association, Inc., 1901 North Fort Myer Drive,

Arlington, VA 22209.

33. "High efficiency residential boilers," Contracting Business 40, 3540,

1983.

34. U. Bonne and A. Patani, "Performance simulation of residential heating

systems with HFLAME III," ASHRAE Trans. 86(1) 351-378, 1980.

35. R. Crenshaw and R. E. Clark, "Optimal weather izat ion of low-income

housing in the U. S.: a research demonstration project," National

Bureau of Standards Building Science Series 144, Washington, 1982.

36. American National Standards Institute (ANSI) and American Society for

Heating, Refrigerating, and Air-Conditioning Engineers, Inc., "Energy

conservation in new building design," ANSI/ASHRAE Standard 90A-1980,

ANSI, New York, ASHRAE, Atlanta, 1980.

37. W. J. Rossiter and R. G. Mathey, "Criteria for retrofit materials and

products for weather izat ion of residences," National Bureau of

Standards Technical Note 952, 1978.

38. W. Gathers, "The warm room concept," Warm Room News 1, Alliance to

Save Energy, Washington, March 1983.

39. M. Perlman and E. A. Thompson, "Effects of installation of heat traps

on energy standby losses of storage-tank water heaters," Ontraio Hydro

Research Division report no. 82-172-K, Toronto, August 31, 1982.

40. R. A. Grot, "Field performance of gas and electric water heaters," pp.

110-120 in "Proceedings of the conference on major home appliance

technology for energy conservation," Purdue University, West

Lafayette, IN, February 27-March 1, 1978; U. S. Department of Energy,

report no. CONF-780238, Washington.

41. Arthur D. Little, Inc., "Study of energy saving options for

refrigerators and water heaters," May 1976.

42. R. A. Hoskins and E. Hirst, "Energy and cost analysis of residential

water heaters," Oak Ridge National Laboratory, report no. ORNL/OON-IO,

Oak Ridge, TN, 1977.

43. R. L. Pal la, Jr., "Evaluation of energy-conserving modifications for

v^ter heaters," National Bureau of Standards Interagency Report 79-

1783, 1979.

40
44. M. Perlman and E. A. Thompson, "Thermal performance and delivery

capability of electric water heaters," Ontraio Hydro Research Division

report no. 81-334-K, Toronto, September 9, 1981.

45. J. E. Harris, "Test results and a recommended test procedure for heat

traps," National Bureau of Standards Interagency Report 84-2851,

Washington, 1984.

46. J. E. Harris, "Performance of add-on type heat pump water heaters

using two different test methods," National Bureau of Standards

Interagency Report 83-2723, Washington, 1983.

47. G. E. Kelly, D. Didion, D. Quigley, and B. Collins, "Potential savings

in residential oil-fired heating systems in the United States,"

draft report,National Bureau of Standards, Washington, 1983.

48. R. P. Blevins, B. D. Sloane and G. E. Valli, "Demonstration of a heatpump water heater," volume 2, Oak Ridge National Laboratory, report

no. ORNL/Sub-7321/4, Oak Ridge, TN, 1981.

49. K.-M. Tu, A. Davies and S. Fischler, "A study of an integrated

appliance, the air conditioner/heat pump-heat recovery unit-water

heater," National Bureau of Standards Interagency Report 80-2145

(DoE) , Washington, 1980.

50. C. W. Erlandson, "Heat recovery water heating," pp. 101-108 in

"Proceedings of the Conference on Waste Heat Recovery for energy

conservation — residential and light commercial heat pumps, air

conditioning, and refrigeration systems, September 15-17, 1980," U. S.

Department of Energy, report no. CONF-800966, Washington.

51. K.-M. Tu and S. Fischler, pp. 55-79 in "Proceedings of the Conference

on Waste Heat Recovery for energy conservation — residential and

light commercial heat pumps, air conditioning, and refrigeration

systems, September 15-17, 1980," U. S. Department of Energy, report

no. CONF-800966, Washington.

52. L. A. Abbatiello, E. A. Nephew and M. L. Ballou, "The performance and

economics of using heat pump desuperheaters for residential water

heating," pp. 18-23 in "Proceedings of the Conference on Waste Heat

Recovery for energy conservation — residential and light commercial

heat pumps, air conditioning, and refrigeration systems, September 15-

17, 1980," U. S. Department of Energy, report no. CONF-800966,

Washington.

53. Florida Solar Energy Center, "Residential conservation demonstration:

Domestic hot vater," Research and Development Division, 300 State Road

401, Cape Canaveral, FL 32920; prepared for Florida Public Service

Commission, Research and Management Studies Department, Residential

Conservation Demonstration Program, 101 East Gaines Street,

Tallahassee, FL, 32301; September 1983.

41
54. R. L. Dunning et al., "Research and development of a heat pump water

heater," volumes 1 and 2, Oak Ridge National Laboratory, report no. ORNL/Sub-7321/1 and 2, Oak Ridge, TN, 1978.

55. Bureau of Labor Statistics, "News," United States Department of Labor,

Washington, July 22, 1983.

56. W. D. Lee and R. Merriam, "Air conditioner-water heater national

potential," pp. 24-28 in "Proceedings of the Conference on Waste Heat

Recovery for energy conservation — residential and light commercial

heat punps, air conditioning, and refrigeration systems, September 15-

17, 1980," U. S. Department of Energy, report no. CONF-800966,

Washington.

57. Trane Co., "Cooling performance testing on common eight year old

residential air conditioning unit," LaCross, WI, May 24, 1976.

58. R. Furness, M. Thedford and J. Houcek, "A research into a new method

of refrigeration charging and effects of improper charging," report

number TS 83-3-1, Texas Power and Light Co., Dallas, October 1983.

59. Bacharach Instrument Co., "Oil burner combustion testing," Bulletin

4011, Pittsburgh, PA, 1975.

60. D. w. Dewerth and S. M. Connelly, "Development and field test of a

method for detecting unacceptable flue gas leakage from heat

exchangers," American Gas Association for the Gas Research Institute,

report no. GRI-83-005, Chicago, 1983.

61. Bacharach Instrument Co., "Bacharach gas burner combustion testing,"

Bulletin 4006, Pittsburgh, PA., 1982.

62. G. F. Sushinsky, "The degradation of gas-fired water heaters,"

National Bureau of Standards Interagency Report 78-1460, Washington,

1978.

63. M. B. Sonnen, "Quality related costs of regional water users," ASCE - Journal of the Hydraulics Division, October 1973.

64. D. P. Tihansky, "Damage assessment of household water quality," ASCE - Journal of the Environmental Engineering Division, August 1974.

65. F. W. Nelson and W. E. Stearns, "Glass lining requirements for

domestic water heaters," Metal Products Manufacturing, January 1962.

66. "Why, When and How To Remove Water Scale From Tank Type Water

Heaters," A. 0. Smith Corporation, Kankakee, IL form no. 4800, rev. 3,

1965.

67. U. S. Environmental Protection Agency, "Guidelines for adjustment of

atmospheric gas burners for residential and commercial space and water

heating," report number EPA-600/8-79-005, Research Triangle Park, NC,

1979.

42
68 . [figure] W. P. Levins, "A comparison of laboratory and field test

measurements of heat pump water heaters," presented at the ACEEE 1982

Summer Study, Santa Cruz, CA, August 21-28, 1982.*

'
Table 1-A Method of reducing energy losses for heating systems

(from Ref. 5)

• On-Perlod Losses

Factors that Influence steady-state losses and efficiency

- burner excess-air level

- flue-gas temperature

- jacket losses

- source and temperature of combustion air

Other factors involved during the on period during intermittent^ operation

- system load

- cycle length

- thermal mass of the furnace/boiler and heating medium

• Off-Period Losses

~ fiir flow through the burner and heat exchanger

- system load

- cycle length

- thermal mass of furnace/boiler and heating medium.

Table 1-B Design routes to high seasonal efficiency

(from Ref. b)

1. Low-excess-air operation

2. Efficient heat exchanger

3. Reduction of burner oversizing

4. Reduction of off-period losses

5. Reduction of jacket losses

6. Reduction of furnace/boiler-induced air infiltration.

44
Table 2. Gas conservation potential of various retrofit options

(fronj Ref. 12)

Type Of

Rptrof it Group

Group-Mean Gas

Consumption

Sites Reduction

Nos. %

+ One Standard

Deviation

or at

70% Confidence Level

'r Two Standard

Deviations

or at

95% Confidence Level

1 D(F+C) * 105 6.2

2 D(F+C)+VR 131 9.1

3 D(F+C)+IID 2 6 .

7

4 D(F+C)+VD+VR+IID 50 12.6

5 D(F) 97 1.5

6 D(F)+VR 19 2.4

7 D(F)+IID

8 VD • 146 5.1

9 VD+IID 122 5.1

'10 VD+VD+IID 31 11.3

11 VR 35 3.7

12 VR + VR 34 7.7

13 IID 24 4.4

14 FHE 52 3.0

15 OA 41 £ -0.6

16 NS 13 4.9

5.2 - 7.2 4.2 - 8.2

8.4 - 9.8 7.7 - 10.5

(-5.2) - 18.6 (17.1) - 30.5

1.09 - 14.3 9.2 — 16.0

0.8 — 2.2 0.1 — 2.9

1.3 — 3.5 0.2 4.6

4.5 . 5.7 3.9 6.3

2.7 - 6.3 3.7 - 6.5

9.4 - 13.5 7.5 — 15.1

2.U — 5.0 1.1 — 6.3

5.9 - 9 .

5

4.1 — 10.5

2.5 6.3 0.6 — 8.2

2.2 - 3.8 1.4 - 4.6

(-1.6) - 0.6 (-2.6) - 1.6

2.0 - 7.9 (-0.9) - 11.8

** SYMBOL

D

F + C

F

IID

VD

VR

VD + VD

VR + VR

FHE

OA

definition

Derating

Fuel and Combustion Air

Fuel Only

Intermittent Ignition Device

Automatic Vent Damper

Fixed Vent Restrictor

Double Damper (one for furnace, the

other for water heater)

Double Vent Restrictor (one for furnace

the other for water heater)

Flue Heat Extractor

Outside Air Connection

Night Setback Clock

45

NS
Table 3. Oil conservation potential of various retrofit options

(from Ref. 21)

o BOILERS REFITTED WITH FLAME RETENTION HEAD BURNERS (RHB)

PROBABLE INSTALLATION/ * 1980 FUEL SAVINGS %

OPTION DESCRIPTION

SERVICE REQUIREMENTS

(SEE LEGEND)

INSTALLED

COST $ TYPICAL VARIATIONS

RHB-ROUTINE REFIT (1) (2) (5) 325 11 7-15

RHB-OPTIMIZED REFIT (1) (2) (5) 390-425 18 16-22

RHB-OPTIMIZED REFIT &

AUTOMATIC BOILER

TEMPERATURE RESET

CONTROL

(1) (2) (5)

i

(3) (5)

665-700 20 15-24 |

RHB-OPTIMIZED REFIT &

VENT DAMPER (TIMED

DELAY, NO BYPASS)

(1) (2) (5)

(1) (3) (5)

685-720 20 16-27

o BOILERS REFITTED WITH OPTIONS NOT INCLUDING A BURNER REPLACEMENT

VENT DAMPER- (TIMED

DELAY, NO BYPASS) (1) (3) (5) 295 9 6-23

FLUE GAS /WATER

HEAT RECLAIMER (4) (3) (5) 520 10 4-17

AUTOMATIC DUAL SETBACK THERMOSTAT(S) (3) (6) (5) 80-155 9 4-14

AUTOMATIC DUAL SETBACK THERMOSTAT(S) & (3) (6) (5) 355-430 19 10-32

AUTOMATIC BOILER

TEMPERATURE RESET

CONTROL (3) (6) (5)

LEGEND:

^Anixial cleaning and adjustments are recommended to assure optimized equipment performance.

^Adjustments, cleaning, repairs , or replacement is generally provided at no additional cost by paid

anrual service agreements with the homeowner and fuel supply/service company.

^Adjustments, repairs, or replacement is generally provided by a separate time and material cost

agreement after warrantee period.

^Cleaning and adjustments are probably needed to frequently optimize the efficiency of the

equipment.

^Homeowner education, direct inputs, and adjustmerts are required for successful operation and maximum

fuel savings.

^Local code authorities may require Installation inspection fees.

*Cost will vary significantly with market area, the marketer, and product brand.

46
Table 4. Energy conservation potential of various water heater retrofit

options. (from Ref. 43)

Modification

Reduce thermostat setting by 10°C

Add 33 nm extra insulation

Reduce thermostat setting and add extra

insulation

Replace original insulation with improved

insulation of the same thickness

Replace original insulation with improved

insulation of increased thickness

Reduce pilot input rate from 200 W to 60 W

Replace pilot with intermittent ignition

Replace pilot with intermittent ignition and

add mechanical flue damper

Add a thermal flue damper

Add a mechanical flue damper

Reduction in Water Heating Energy

RequirementsA - %

Electric Gas Oil

11, (9) 13 12 [12]

7, (3) 7 9 [9]

(11) 18 19

4 3 2

9 10

1,2 -

4 ,6,(3) —

11,16,(10)

"

3, (2) —

U*l®

A - Parentheses ( ) indicate results for energy conserving models,

brackets [ ] indicate results for external-flue water heater

B - Assumes a damper with zero leakage installed at the flue

47
Table 5. Energy conservation potential of various water heater design changes

(from Ref. 42)

. 0.19 m

3 (50 gal) Electric 0.15 m

3 (40 gal) Gas

% Energy % Cost % Energy % Cost Savings Increase Savings Increasi

1 . Increase jacket insulation to

a) 5.1 cm fiberglass 7 3 b) 7.6 cm fiberglass 4 4 10 6 c) 10.2 cm fiberglass 7 8 10 10

d) 12.7 cm fiberglass 7 12 11 14

2. Reduce jacket insulation thermal

conductivity

a) 2.5 cm urethane 9 4 b) 5.1 cm urethane 8 6 12 8 c) 7.6 cm urethane 10 11 13 10

d) 10.2 cm urethane 11 14 13 13

e) 12.7 cm urethane 11 17 13 16

3. Reduce thermostat setting 5.6°C 5 0 5 0

4. Add insulation to 7.6 m of distribution

pipe

a) 1.3 cm fiberglass 3 9 3 9 b) 2.5 cm fiberglass 3 10 3 9

5. Reduce pilot rate from 6.9 x 109 J/yr to

3.7 x 10 9 J/yr ui.SU 6 0

6. Eliminate pilot — add electric ignitor

and flue closure 12 84

7. Reduce excess air for combustion 3 1

8. 2d, 4b 14 24 16 23

9. 2e, 3, 4b 17 27 18 25

10. 2d, 4b, 5, 7 24 23

11. 2e, 3, 4b, 5, 7 27 26

Baseline 23.9 x 109 J/yr $157 37.7 x 10 9 J/yr $168

48
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NT • a) O oo o rtf rH <r CN X3H

<rO co

H

N

H

H

X

X CO v*

oo i—i o o o o o o o in

oo ON OOX 40-oX3

-u

CJ

0) I—I wc

(U>co

cj 3 s 3 a)

4-1 4J

to co a) ph

PS co 3 3

a) a)

to co 3 3 |

Pu

cOa) PC

4-1 o

PC

1-1

l-i 3

CO 4-1 X CO O CO CO 3

49

Heat

Recovery

Unit

650
Table 7. Annual Dollar -Savings for S100 of Annual Fuel Tnsf

as a result n£ Tnrr.pafipH Furnace Efficiency*

(from Reference 7)

From original

efficiency* of

(Percent)

1 74

To

76

an Increased efficiency of (percent)

78 80 82 84 86

50 $32.40 $34.20 $35.90 $37.50 $39.00 $40.50 $41.90

52 29.70 31.60 33.30 35.00 36.60 38.10 39.50

54 27.00 28.90 30.80 32.50 34.10 35.70 37.20

56 24.30 26.30 28.20 30.00 31.70 33.30 34.90

58 21.60 23.70 25.60 27.50 29.30 31.00 32.60

60 18.90 21.10 23.10 25.00 26.80 28.60 30.20

62 16.20 18.40 20.50 22.50 24.40 26.20 27.90

64 13.50 15.80 17.90 20.00 22.00 23.80 25.60

66 10.80 13.20 15.40 17.50 19.50 21.40 23.30

68 8.10 10.50 12.80 15.00 17.10 19.00 20.90

70 5.40 7.90 10.30 12.50 14.60 16.70 18.60

72 2.70 5.30 7.70 10.00 12.20 14.30 16.30

74 2.60 5.10 7.50 9.80 11.90 14.00

76 2.60 5.00 7.30 9.50 11.60

*Efficiency is the steady state efficiency measured from the flue gas

, temperature and CO2 or Oxygen concentration.

50
Figure 1. Recommended Approach for Retrofit of Space Heating Systems

51
Figure 2. Recommended approach for retrofit of water heaters

52
100

Steady

State

*

>

ocV5

£

LU

"5

W.0>>o

Burner Fractional "On" Time 7-0n

..°

n„Jj.TM ime <%>

Effect of Improved

Burner

— Showing effect of boiler design and burner performance — Boiler maintained at temperature for water-heating coil.

Fig. 3. Part-load efficiency in direct input/output tests

(from Reference 5)

53
Fig. 4. Energy flow diagram for a gas furnace system

(from Reference 9)

54
Fig. 5. Schematic of air supply and venting in furnace and water heater

(from Refrence &')'

Fig. 6. Schematic of aquabooster water heater

(from Ref. 18)

55
COMBUSTION AIR INLET

AIR FAN

Figure 7. Flame Retention Head Oil Burner

(from Ref. 48)

56
A direct measurement method has been proposed as a potential alternative to

the tracer gas technique now used to measure off-period energy loss of space

heating equipment because the alternative does not require expensive tracer

gas instrumentation. The method uses a controlled flow of gas to a small gas fuel burner to simulate normal flue or stack temperatures previously

measured during a cool-down test. Energy metered through the gas burner

during the simulation gives a direct measurement of the thermal energy losses

out of the stack. The tests made to evaluate the method indicate that the

simulated temperature vs time profile usually results in a lower value of

off cycle energy loss than a normal cool-down while the measurement of the

BTU's required for the simulation (bunsen burner fuel use) was eratic but

frequently resulted in a larger energy loss evaluation. Further development

testing and evaluation will be required before the simulation system can be

considered as an acceptable alternative test method.

SL (\

Fig. 8-a. Diagram of a boiler vith vent damper

(from Ref . 6)

Fig. 8-b . Diagram of a common manifold vent damper installation

(from Ref. 6)

57
Fig.9-a. Diagram of a thermaly actuated vent damper

(from Ref. 22)

Fig.9-b. Diagram of an electric vent damper

(from Ref. 6)

58
I

ip

.

10

.

Diagram

of

the

flow

paths

In

a

flue

gas

heat

recovery

system

(from

Product

Literature

of

Ther

Heat

Extractor

Corp)
o

Flue gases © coming from your furnace are extremely hot. these gases pass through water sprays ®. The gases are cooled and the water is heated. The

cooled gases © are expelled through a PVC vent pipe @. Heated water in the Efficiency

Booster’s reservoir © is pumped by a hiqh-efficiency electric pump © through the heat

exchanger coil ® . Your furnace blower ® draws cool household air through the heat ex- changer coil, where it is pre-heated before entering the furnace.

Fig. 11. Example of one type of flue gas heat recovery system (Carrier)

(from Product Literature of the Carrier Corp)

60
NOTE: THE ABOVE DRAWINGS ARE NOT TO THE SAME SCALE

ig . 12. Diagrams of heat traps

(Ref. 45)

61
CUTAWAY VIEW OF

HEAT PUMP WATER HEATER

Cold water

inlet Oram valve

Fi g . 1 3 . Diagram of heat pump water heater with integral condenser

Shutoff

P/T Relief va| Ve

Fi g . 1 4 . Diagram o f a separated type of heat pump water heater (from Ref. 53)

62
Shutoff

Cold

Water

In

Electric water heater

Figure 15a Electric resistance water heater

15 .b . Waste heat recovery unit

Fig . 15 . Diagrams of an electric resis tance water heater witho u t and with

ja waste heat recovery unit

(from Ref. 53)

63
Coefficient

of

Performance

Fig. 16. Monthly coefficient- of performance of four different water heating

systems in four Florida cities

(from Ref. 53)

64
c*

z

—•

D2>3ma

OUTDOOR AMBIENT TEMPERATURE (F)

LEGEND-. CHAR.C6 — — - OVER, PKOTEF ^

A- A UhOEK

Char,or

Figure 17. Effect of Refrigerant Overcharge or Undercharge on System

Performance Compared With Proper Charge.

(from Ref. 58)

65
NBS-114A (REV. 2 -80 ) U.S. DEPT. OF COMM.

ifT"1 v: ;

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No, 3. Publication Date NBSIR 84-2870 June 1984

4. TITLE AND SUBTITLE

PERFORMANCE AND SELECTION CRITERIA FOR MECHANICAL ENERGY SAVING RETROFIT

OPTIONS FOR SINGLE-FAMILY RESIDENCES

5.

AUTHOR(S)

Esher Kweller; Samuel Silberstein

6.

PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE *. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

DOE Office of Conservation and Renewable Energy

Weatherization Assistance Program Division

10. SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a slgnifWvnt

bibliography or literature survey, mention it here)

Under the Weather izat ion Assistance Program the U. S. Department of Energy

(DoE) provides funds for energy-conserving building improvements in homes of

low-income persons. In proposing to modify the program to also provide funds

for energy—con serv ing mechanical options, DoE requested that the National

bureau of Standards investigate energy-conserving mechanical options that may

be suitable for inclusion in the Weatherization Assistance Program. This

report estimates energy savings, and provides performance and selection

criteria, standards, and installed costs for mechanical equipment options for

single-family homes; all from prior studies reported in the literature.

Performance and selection criteria are presented as advantages, disadvantages

and limitations for each option.

Four broad categories of energy-sav ing mechanics 1 options were investigated:

space heating, water heating retrofit options, heat pump water heaters, and

recovery of central air conditioner waste heat by desuperheaters. Gas- and

oil-fueled forced-air furnaces and hydronic (hot water) space-heating equipment were treated in this report.

,12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and seoarate kev words bv semicolon s) derating; desuperheaters; energy conservation; heat pump water heaters;

insulation; mechanical equipment; retrofits; space heating; vent dampers; waste

neat recovery; water heating; weatherization

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

[X] Unlimited

Q3! For Official Distribution. Do Not Release to NTIS

1 Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

74

15. Price

[XU Order From National Technical Information Service (NTIS), Springfield, VA. 22161 66 $10.00

U S COMM* DC 0043-PS0