## WATER HEATER TEST PROCEDURE RULEMAKING:

DEVELOPMENT TESTING PRELIMINARY REPORT

ENERGY CONSERVATION PROGRAM FOR CONSUMER PRODUCTS AND CERTAIN INDUSTRIAL EQUIPMENT:

Residential and Light Commercial Water Heaters

November 2013

U.S. Department of Energy Assistant Secretary Office of Energy Efficiency and Renewable Energy Building Technologies Program Appliances and Commercial Equipment Standards Washington, DC 205852 Th is Document was prepared for the Department of Energy

b y staff members of Navigant Consulting, Inc. and The National Institute of Standards and Technology3 WATER HEATER T ES T PROCEDURE RULEMAKING: DEVELOPMENT TESTING PRELIMINARY REPORT

TABLE OF CONTENTS

1. Introduction ............................................................................................................................. 6

1.1. Current Test Procedure ................................................................................................... 6 1.2. The Proposed Test Procedure ......................................................................................... 9

1.3. Tested Products ............................................................................................................. 11

2. Impact on First-Hour Rating of Storage Water Heaters ....................................................... 13

3. Impact on Maximum GPM Rating of Instantaneous Water Heaters .................................... 15

4. Impact on Energy Factor ....................................................................................................... 17

4.1. Storage Water Heaters

................................ ................................ ................................ .. 17

4.2. Instantaneous Water heaters ......................................................................................... 19

5. Effects of Proposed Test Procedure on Different Categories of Water Heater .................... 21

5.1. Storage Water Heaters

................................ ................................ ................................ .. 21

5.2. Instantaneous Water Heaters ......................................................................................... 22

6. Variance in Energy Factor Ratings for Water Heaters Under Different Draw Profiles ....... 23

6.1. By Water Heater Type

................................ ................................ ................................ .. 23

6.2. By Energy Source

................................ ................................ ................................ ......... 25

6.3. B y Applicable Draw Profile

................................ ................................ .......................... 27

7. Summary ............................................................................................................................... 304 LIST OF TABLES Table 1: 24-hour simulated use test draw profile criteria for storage water heaters ........................9

Ta ble 2: 24-hour simulated use test draw profile criteria for instantaneous water heaters ..............9 Table 3: 24-hour simulated use test draw profiles for proposed test procedure ............................10

Ta ble 4: Products used in residential water heater test report .......................................................11

Ta ble 5: Averaged first-hour rating of storage water heaters under proposed test

procedure as percentage of current first-hour rating, categorized by energy source and applicable draw profile ........................................................................21 Table 6: Averaged energy factor of storage water heaters under proposed test procedure

as percentage of current energy factor, categorized by energy source and applicable draw profile ..........................................................................................21

Ta ble 7: Averaged maximum gpm rating of instantaneous water heaters under proposed

test procedure as percentage of current maximum gpm rating, categorized by energy source and applicable draw profile .......................................................22

Ta ble 8: Averaged energy factor of instantaneous water heaters under proposed test

procedure as percentage of current energy factor, categorized by energy source and applicable draw profile ........................................................................22

LIST OF FIGURES
Figure 1: First-hour rating of storage water heaters under proposed test procedure as

percentage of current first-hour rating, as function of current first-hour rating ......................................................................................................................13

F igure 2: First-hour rating of storage water heaters under proposed test procedure as

percentage of current first-hour rating, as function of applicable draw profile .....................................................................................................................14 Figure 3: Maximum gpm rating of instantaneous heaters under proposed test procedure as

pe rcentage of current maximum gpm rating, as function of current maximum gpm rating .............................................................................................15

F igure 4: Maximum gpm rating of instantaneous water heaters under proposed test

procedure as percentage of current maximum gpm rating, as function of draw profile established by the proposed maximum gpm rating test ....................16 Figure 5: Energy factor of storage water heaters under proposed test procedure as

percentage of current energy factor, as function of current energy factor .............18 Figure 6: Energy factor of storage water heaters under proposed test procedure as

percentage of current energy factor, as function of applicable draw profile .........18 Figure 7: Energy factor of instantaneous water heaters under proposed test procedure as

percentage of current energy factor, as function of current energy factor .............195

Figure 8: Energy factor of instantaneous water heaters under proposed test procedure as

percentage of current energy factor, as function of applicable draw profile .........20 Figure 9: Energy factor ratings of storage water heaters tested with different draw profiles

(heat pump water heater S- HP -1 excluded) ...........................................................24

F igure 10: Energy factor ratings of storage heat pump water heater S- HP

- 1 tested with

different draw profiles............................................................................................24

F igure 11: Energy factor ratings for instantaneous water heaters tested with different

draw profiles ..........................................................................................................25 Figure 12: Energy factor ratings for water heaters using natural gas as an energy source ............26 Figure 13: Energy factor ratings for water heaters using oil as an energy source .........................26

F igure 14: Energy factor ratings for water heaters using electricity as an energy source .............27 Figure 15: Energy factor ratings for water heaters testing for point of use draw profile ..............28 Figure 16: Energy factor ratings for water heaters testing for low usage draw profile (heat

pump water heater S- HP -1 excluded) ....................................................................28 Figure 17: Energy factor ratings for water heaters testing for medium usage draw profile ..........29 Figure 18: Energy factor ratings for water heaters testing for high usage draw profile ................296 WATER HEATER TES T PROCEDURE RULEMAKING: DEVELOPMENT TESTING PRELIMINARY REPORT

1. INTRODUCTION
The American Energy Manufacturing and Technical Corrections Act (AEMTCA) requires DOE to establish a uniform efficiency descriptor for covered water heaters. (42 U.S.C. 6295(e)(5)) Consequently, the U.S. Department of Energy (DOE) initiated a rulemaking to consider

a mendments to its existing test procedures for covered residential and commercial water heaters. As part of this effort, DOE conducted a series of tests to assess the impact of proposed revisions

a nd additions to the current DOE test procedures for residential water heaters and certain

c ommercial water heaters. The purpose of the testing is to validate the pr oposed test method (78 FR 66201) and examine the impact of the proposed test procedure revisions on the first-hour

ra ting of storage water heaters, maximum gallons per minute rating of instantaneous water he aters, and energy factor of both storage and instantaneous water heaters. In addition, the test results were used to assess the variability in the energy factor based on the draw profile selected, as well as the impact of the proposed amendments on different types of water heaters. DOE collected and analyzed data on the energy factor, first hour rating (for storage water heaters), and

max imum gallon per minute (max gpm, for instantaneous water heaters) of a number of different types of water heaters for this report, and consider ed the following impacts:

 Impact of test procedure revisions and additions on first hour rating of residential storage

wa ter heaters

 Impact on maximum gallon per minute of instantaneous water heaters

 Impact on energy factor of all water heaters

 Effects on different categories of water heater ( e.g. , gas- fi red storage, electric storage,
g as-fired instantaneous, etc.)

 Variance in energy factor ratings of water heaters tested under different draw profiles ( e.g. , point of use, low usage, etc.)

1.1. CURRENT TEST PROCEDU RE

Residential Water Heaters

The current DOE test procedure for residential water heaters (10 CFR 430, Subpart B, Appendix E ) provides test protocols for storage water heaters to be tested for a first-hour and energy factor

ra ting, and for instantaneous residential water heaters to be tested for a max im um gpm and energy factor rating. The first-hour rating test measures the volume of hot water that can be de livered by a storage water heater in a single hour, while the maximum gpm rating reflects the maximum flow rate at which an instantaneous water heater can continuously deliver hot water at a useful temperature. The energy factor rating test measures overall water heater efficiency7

(including active, standby, and cycling operation) over a 24-hour period at a specific set of rating conditions and single draw profile.
Under current testing procedure, the ambient air temperature during all tests (first hour, max
g pm, and energy factor) must be maintained between 65°F and 70°F, the inlet water temperature
must be 58°F ± 2°F, and the thermostat must be adjusted to a setting that achieves a mean int ernal storage tank temperature of 135°F ± 5°F.

For the first-hour rating test, the storage water heater is allowed to operate until it is at an

a verage internal tank temperature of 135°F ± 5°F. Once the target tank temperature is achieved, the test begins and hot water is drawn at a rate of 3.0 gpm until the outlet temperature of the

wa ter exiting the storage tank decreases to 25°F less than the maximum observed outlet temperature. Subsequent draws begin when the thermostat acts to reduce the supply of heat

e nergy to the storage tank and continue until the outlet temperature of the water exiting the storage tank decreases to 25°F less than the maximum observed outlet temperature for the given draw. This process is repeated for a total time of one hour. At the end of the hour, if a draw is in
pr ogress, that draw is allowed to complete normally (i.e., until the outlet temperature of water exiting the storage tank decreases to 25°F less than the maximum observed outlet temperature). If a draw is not occurring, a final draw is initiated and then terminated when the outlet water temperature reaches the same outlet temperature that the previous draw was terminated at. The first-hour rating is then calculated as the total volume of hot water drawn over this period (in
g allons), and is a function of both the storage volume and water heater recovery rate.

I n the maximum gpm test, after the thermostat is adjusted to a set point that achieves an outlet temperature of 135°F ± 5°F, water is drawn from the instantaneous water heater for a total time of 10 minutes at the maximum possible flow rate while maintaining the target set point temperature. The maximum gpm rating is calculated as the total volume of water drawn over this
pe riod (in gallons) divided by ten minutes

. The energy factor rating is determined from a 24-hour simulated use test. In this test a total of 64.3 g allons of water are removed from the water heater at a rate of 3.0 gpm over six equal draw periods. a Initially, the water heater is operated at a set point that achieves an average internal tempe rature of 135°F ± 5°F for storage water heaters or provides an outlet temperature of 135°F ± 5°F for instantaneous water heaters. At the start of the test, a volume of water equal to onesixt h of 64.3 gallons is drawn. Another draw equal to one-sixth of 64.3 gallons is drawn at the start of the each subsequent hour and continues for a total of six draws. After the sixth draw, the

wa ter heater is left in standby mode until 24 hours have elapsed from the start of the test. The energy factor of the water heater is then calculated as the total energy contained in the delivered hot water divided by the total energy the water heater consumed during the 24 -hour test period. The energy factor is a function of several intermediate metrics, such as recovery efficiency and

a If an instantaneous water heater cannot deliver water at 3.0 GPM and a temperature of 135°F±5°F, then the water flow rate is reduced such that the discharge temperature is 135°F±5°F and heater firing rate is maximized.8

standby loss, and is normalized for differences from the nominal test parameters that occur during testing. b

Commercial Water Heaters
The current test procedure for commercial water heaters is specified at 10 CFR 431.106 and references the American National Standards Institute (ANSI) Z21.10.3-2011, “Gas Water Heaters, Volume III, Storage Water Heaters with Input Ratings above 75,000 Btu per Hour, Circulating and Instantaneous.” The DOE test procedure provides a method to determine the ther mal efficiency and standby loss for gas-fired and oil-fired storage and instantaneous water heaters, and to determine the standby loss for electric storage and instantaneous water heaters.

For determining thermal efficiency, the DOE test method requires that the thermostat first be adjusted so that the maximum mean tank temperature after cut-out is 140°F ± 5°F. Inlet water is supplied at 70°F ± 2°F and the ambient air temperature is maintained 75 °F ± 10°F. Water is drawn from the water heater and the flow rate of the water being drawn is adjusted until the temperature is a constant 70°F ± 2°F above the supply water temperature. Once the outlet temperature becomes constant, as determined by no variation in excess of more than 2°F over a 3 minute period, the outlet water is diverted to a weighing container for exactly 30 minutes. G as or oil and/or electrical consumption are metered over the 30 minute period, and the water is

w eighed at the end of the test. In addition, inlet and outlet water temperature measurements are recorded during the test, as well as the temperature, pressure, and heating value of the fuel and ba rometric pressure. Thermal efficiency is then calculated as the ratio of the energy in the delivered hot water to the total fossil fuel and electrical energy consumed during the test period.

F or determining standby loss, the DOE test method requires that the water heater be set up as described for the thermal efficiency test. The water heater is then put into operation and after the second cut-out the test begins. The test continues until either (1) the first cutout after 24 hours or (2) 48 hours if the water heater is not in the heating mode at that time, whichever happens first. Eve ry 15 minutes during the test, the ambient air temperature and mean tank temperature are recorded, and at the end of the test the total fuel and/or electrical consumption is recorded. The standb y loss (as a percent) is then calculated as the ratio of average hourly energy consumption to the heat content of the stored water above room temperature. For gas and oil water heaters, the standby loss percentage is then tabulated in Btu per hour.

b Adjustments are made to account for the fact that the temperature difference between the storage tank and surrounding ambient air may not be the nominal 67.5°F due to the 10°F allowable variation in storage tank temperature (for storage water heaters) or discharge temperature (for instantaneous water heaters) and the 5°F allowable variation in ambient air temperature. Another adjustment is made to take into account that the temperature difference between the outlet and supply water may not be equivalent to the nominal value of 77°F due to tolerances in the inlet water temperature and allowable variation in the storage tank temperature (for storage water heaters) or discharge water temperature (for instantaneous water heaters).9

1.2. THE PROPOSED TEST PROCEDURE
DOE has expanded the test procedure scope to include electric instantaneous water heaters, water he aters with between 2 and 20 gallons of storage volume, and gas-fired and oil-fired storage water heaters with storage volumes up to 120 gallons. The test method also covers certain commercial equipment that meet the definition of “light commercial” water heaters proposed in the notice of proposed rulemaking. Additionally, the proposed DOE method would lower the set point temperature to 125°F, rather than 135°F, while requiring water flow rates to vary for each draw during the 24-hour simulated use test. Test conditions for inlet water and ambient air temperature are still prescribed as 58°F and 67.5°F, respectively.

F or storage water heaters, the proposed first-hour rating test is generally conducted in the same

manne r as the current test procedure, but the target set point temperature is now 125°F and water dr aws are terminated when the outlet water temperature drops 15°F from its maximum value in stead of 25°F. In addition, the result of the first-hour rating is then used to select the draw pattern used for the 24-hour simulated use test, summarized in Table 1 below

. Table 1: 24-hour simulated use test draw profile criteria for storage water heaters

First hour rating greater than or equal to: ... And First Hour Rating less than... D raw pattern to be used in 24

- hour simulated use test 0 gal 20 Point of use

20 5 5 Low usage

5 5 8 0 Medium usage

8 0 No limit High usage

For instantaneous water heaters, the proposed maximum gpm rating test is generally the same as the c urrent test, except for the decrease in water discharge temperature from 135°F to 125°F. c As in the first-hour rating test for storage water heaters, the result of the maximum gpm test is now used to select the draw pattern for the 24-hour simulated use test, summarized in Table 2 below.

Table 2: 24-hour simulated use test draw profile criteria for instantaneous water heaters

Max GPM rating greater than or equal to: ... And max GPM rating less than... Draw pattern to be used in 24

- hour simulated use test

0 GPM 1. 7 Point of use

1. 7 2

. 8 Low usage

2

. 8 4.0 Medium usage

4.0 No limit High usage

c Under the proposed test, if an instantaneous water heater cannot deliver water at 2.0 GPM and 125°F ± 5°F, then its flow rate is reduced such that the discharge temperature is 125°F ± 5°F and its heater firing rate is maximized.10

Based on the performance of the storage water heater in the first-hour rating test or the inst antaneous water heater in the maximum gpm test, the unit is classified into one of four

c ategories to reflect its expected use in the field–point of use, low usage, medium usage, and high usage. Each category is subject to a unique draw profile, summarized in Table 3

. Table 3: 24-hour simulated use test draw profile s f or proposed test procedure

1. Point of Use Draw Pattern

Draw
Number Time During

Test ( hh:mm ) Volume

(gallons) Flow

Rate (GPM ) 1* 0:00 2.0 (7.6) 1 (3.8)
2* 1:00 1.0 (3.8) 1 (3.8)
3* 1:05 0.5 (1.9) 1 (3.8)
4* 1:10 0.5 (1.9) 1 (3.8)
5* 1:15 0.5 (1.9) 1 (3.8)
6 8:00 1.0 (3.8) 1 (3.8)
7 8:15 2.0 (7.6) 1 (3.8)
8 9:00 1.5 (5.7) 1 (3.8)
9 9:15 1.0 (3.8) 1 (3.8) Total Volume Drawn Per Day: 10 gallons (38 L)
* Denotes draws in first draw cluster. 2. Low Usage Draw Pattern

Draw
Number Time During

Test (hh:mm) Volume

(gallons) Flow

Rate ( GPM ) 1* 0:00 15.0 (56.8) 1.7 (6.5)
2* 0:30 2.0 (7.6) 1 (3.8)
3* 1:00 1.0 (3.8) 1 (3.8)
4 10:30 6.0 (22.7) 1.7 (6.5)
5 11:30 4.0 (15.1) 1.7 (6.5)
6 12:00 1.0 (3.8) 1 (3.8)
7 12:45 1.0 (3.8) 1 (3.8)
8 12:50 1.0 (3.8) 1 (3.8)
9 16:15 2.0 (7.6) 1 (3.8)
10 16:45 2.0 (7.6) 1.7 (6.5)
11 17:00 3.0 (11.4) 1.7 (6.5) Total Volume Drawn Per Day: 38 gallons (144 L)
* Denotes draws in first draw cluster.

3. Medium Usage Draw Pattern

Draw
Number Time

During Test (hh:mm) Volume

(gallons) Flow

Rate ( GPM ) 1* 0:00 15.0 (56.8) 1.7 (6.5)
2* 0:30 2.0 (7.6) 1 (3.8)
3* 1:40 9.0 (34.1) 1.7 (6.5)
4 10:30 9.0 (34.1) 1.7 (6.5)
5 11:30 5.0 (18.9) 1.7 (6.5)
6 12:00 1.0 (3.8) 1 (3.8)
7 12:45 1.0 (3.8) 1 (3.8)
8 12:50 1.0 (3.8) 1 (3.8)
9 16:00 1.0 (3.8) 1 (3.8)
10 16:15 2.0 (7.6) 1 (3.8)
11 16:45 2.0 (7.6) 1.7 (6.5)
12 17:00 7.0 (26.5) 1.7 (6.5) Total Volume Drawn Per Day: 55 gallons (208 L)
* Denotes draws in first draw cluster. 4. High Usage Draw Pattern

Draw
Number Time

During Test (hh:mm) Volume

(gallons) Flow

Rate ( GPM ) 1* 0:00 27.0 (102) 3 (11.4)
2* 0:30 2.0 (7.6) 1 (3.8)
3* 0:40 1.0 (3.8) 1 (3.8)
4* 1:40 9.0 (34.1) 1.7 (6.5)
5 10:30 15.0 (56.8) 3 (11.4)
6 11:30 5.0 (18.9) 1.7 (6.5)
7 12:00 1.0 (3.8) 1 (3.8)
8 12:45 1.0 (3.8) 1 (3.8)
9 12:50 1.0 (3.8) 1 (3.8)
10 16:00 2.0 (7.6) 1 (3.8)
11 16:15 2.0 (7.6) 1 (3.8)
12 16:30 2.0 (7.6) 1.7 (6.5)
13 16:45 2.0 (7.6) 1.7 (6.5)
14 17:00 14.0 (53.0) 3 (11.4) Total Volume Drawn Per Day: 84 gallons (318 L)
* Denotes draws in first draw cluster.11

As with the current test method, the energy factor of the water heater is calculated as the total heat energy of delivered water divided by the total energy the water heater consumes throughout the 24 -hour simulated use test. Energy consumption rates are also modified to take into account that the difference between storage tank and ambient temperature may not be the nominal 57.5°F, and the difference between inlet and outlet water temperature may not be the nominal value of 67°F.

1.3. TESTED PRODUCTS
To validate the proposed test method and explore the impacts of the proposed test procedure on first-hour rating, DOE tested fifteen storage water heaters and six instantaneous water heaters. Ta ble 4 lists the twenty-one units along with their relevant attributes used in this analysis.

T able 4: Products used in residential water heater test report

Water Heater ID Heater

Type Energy

Source Rated Storage

Volume (gal) Rated Input Notes

S

- NG

- 1 Storage Natural
gas 40 40 k Btu /h

S

- NG

- 2 Storage Natural
gas 29 60 kBtu/h

S

- NG

- 3 Storage Natural
gas 75 70 kBtu/h

S

- NG

- 4 Storage Natural
gas 40 40 kBtu/h

S

- NG

- 5 Storage Natural
gas 40 40 kBtu/h

S

- O

- 1 Storage Oil 32 104 kBtu/h

S

- O

- 2 Storage Oil 32 104 kBtu/h

S

- E

- 1 Storage Electric 30 4.5 kW

S

- E

- 2 Storage Electric 50 4.5 kW

S

- E

- 3 Storage Electric 80 4.5 kW

S

- E

- 4 Storage Electric 4 1.5 kW Not covered by the current DOE test procedure

S

- E

- 5 Storage Electric 6 2 kW Not covered by the current DOE test procedure

S

- E

- 6 Storage Electric 2.75 1.5 kW Not covered by the current DOE test procedure12

S

- E

- 7 Storage Electric 80 4.5 kW

S

- HP

- 1 Storage Heat pump* 50 4.5 kW

I

- NG

- 1 Instantaneo

us Natural

gas 0 199 kBtu/h

I

- NG

- 2 Instantaneo

us Natural

gas** 0 150 kBtu/h

I

- NG

- 3 Instantaneo

us Natural

gas 0 175 kBtu/h

I

- E

- 1 Instantaneo

us Electric 0 3.5 kW

I

- E

- 2 Instantaneo

us Electric 0 12 kW

I

- E

- 3 Instantaneo

us Electric 0 28.8 kW Not covered by the current DOE test procedure

* Water heater S- HP -1 is electric- and heat pump-powered, and includes storage tank.

* * Note that propane gas is an alternative energy source for water heater I- NG -2.13

2. IMPACT ON FIRST-HOUR RATING OF STORAGE WATER HEATERS
DOE tested fifteen storage water heaters for first hour rating under the proposed amended test procedure, including five natural gas-fired, two oil-fired, seven electric resistance-powered, and

one heat pump-powered. For the twelve storage water heater models that are covered by the

c urrent DOE test procedure, DOE compared the measured first-hour ratings under the existing test proc edure to the first hour ratings observed under the proposed revised test procedure, as shown in F igure 1 below. d Five out of the twelve saw their first-hour rating decrease from thecurrent to the proposed test procedure, while the remaining seven water heaters saw their firsthour rating increase. On average, storage water heater measured first-hour ratings under the
propos ed test procedure are 103 % o f their current measured value. From Figure 1 below, the majority of water heaters see their measured first-hour rating change to between approximately 90 % and 110% of their measured rating under the current test method.

F igure 1: First-hour rating of storage water heaters under proposed test procedure as
p ercentage of current first-hour rating, as function of current first-hour rating

DOE also investigated the change in measured first-hour rating of water heaters in different draw
pr ofile categories. Figure 2 below categorizes the twelve applicable storage water heaters into their corresponding draw profile based on first-hour rating test results under the proposed test
pr ocedure. It appears from Figure 2 that the measured first-hour rating of high usage water heaters increases from the current to proposed test procedure, while low usage and medium usage water heaters see their measured first-hour rating either drop or remain relatively constant.

d Water heaters S-E-4, S-E-5, and S-E-6 do not have current first-hour or energy factor ratings since they have a storage volume between 2 and 20 gallons, and fall in a category not currently addressed by the DOE test procedure.

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

0 20 40 60 80 100 120 140 160 180First-hour rating under new test procedure aspercentage of rating under current test

First

- hour rating under current test procedure

Natural gas Oil Electric Heat pump Line of equivalence14

Figure 2: First-hour rating of storage water heaters under proposed test procedure as
p ercentage of current first-hour rating, as function of applicable draw profile

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

0.0 1.0 2.0 3.0 4.0First-hour rating under new test procedure aspercentage of rating under current test

Applicable draw profile under new test procedure

Natural gas Oil Electric Heat pump Line of equivalence

Point of use Low usage Medium usage High usage15

3. IMPACT ON MAXIMUM GPM RATING OF INSTANTANEOUS WATER HEATERS

To determine the impact of the differences between the current and the proposed test procedure s on the measured max gpm, DOE tested six instantaneous water heaters including three natural gas-powered and three electric-powered. Although one of the electric water heaters (I-E-3) is

c urrently outside of the scope of the DOE test method for residential water heaters, DOE was able to perform the current max gpm test on that water heater without modification, and as such, included that unit in the comparison between the current and proposed test method. e Similar to the analysis of first-hour ratings of storage water heaters in Section 2 , DOE compared the change in measured maximum gpm of instantaneous water heaters under the proposed test procedure to the measured maximum gpm under the current test procedure. Figure 3 below plots the measured maximum gpm under the proposed test procedure as a percentage of the measured maximum
g pm under the current test procedure. From this figure, the three electric instantaneous water he aters saw an increase in their measured maximum gpm rating of 14 % on average, while the three natural gas instantaneous water heaters saw an increase of 1 3 %.

Figure 3: Maximum gpm rating of instantaneous heaters under proposed test procedure as
p ercentage of current maximum gpm rating, as function of current maximum gpm rating

The instantaneous water heaters observed in this study are also categorized into their applicable draw pattern based on maximum gpm test results. The measured maximum gpm under the

e The unit I-E-3 would be covered under the proposed revised test method.16

propo sed test procedure as a percentage of the measured maximum gpm under the current test
pr ocedure is plotted as a function of the draw profile in F igure 4 below. As expected, the measured maximum gpm of instantaneous water heaters increases as the set point temperature drops from 135°F to 125°F from the current to proposed test procedure.

Figure 4: Maximum gpm rating of instantaneous water heaters under proposed test
p rocedure as percentage of current maximum gpm rating, as function of draw profile

e stablished by the proposed maximum gpm rating test17

4. IMPACT ON ENERGY FACTOR

DO E investigated the impact of the proposed test procedure on the energy factor of both storage

a nd instantaneous water heaters. Based on the performance of the water heater in the proposed first-hour rating or maximum gpm test (as shown in Section s 2 and 3 ), DOE subjected each water heater to the appropriate draw profile as specified by the proposed test method . DOE also subjected each water heater to at least one other draw profile to better understand how the energy fa ctor of a specific water heater model varies across different draw profiles, the analysis of which is presented in Section 6

. The additional draw profile(s) tested were the pattern directly above and/or below the nominal usage pattern that the unit would qualify for. For example, if a unit qualified for the high usage pattern based on its first hour rating, it was also tested using the medium usage pattern. In several cases, DOE performed additional experimental testing at draw patterns two levels above the nominal pattern ( e.g. , for a unit with a low usage nominal pattern, DOE also performed testing at the high usage pattern) to analyze the trend in the impact on measured energy factor across multiple draw patterns. f

4.1. STORAGE WATER HEATER S

The impact of the differences between the current and proposed test procedure on the measured energy factor was examined for all twelve of the storage water heaters to which the current test
pr ocedure is applicable. g As shown in Figure 5 below, the measured energy factor of six of the twelve storage water heaters increased under the proposed test method, while the measured energy factor of five water heaters decreased and one stayed constant.

Results for storage water heaters are also categorized by their applicable draw profile identified using the measured first-hour rating under the proposed test procedure. From Figure 6 , all water he aters subject to a low or medium usage draw profile experience a decrease in measured energy factor, while the majority of those water heaters subject to a high usage draw profile experience an increase in measured energy factor. This is to be expected, as the energy factor of storage water heaters is correlated to the total volume drawn from the 24-hour simulated use test. Since the high usage test under the proposed procedure draws a higher total volume of water than the current test procedure, one would expect the energy factor to rise. Conversely, the low and medium usag e tests under the proposed procedure draw less water than required by the current
test m ethod, and one would expect their energy factors to fall.

f Additionally, some water heaters were ori ginally grouped into different draw profile bins than they are currently. This is because DOE adjusted the draw profile first

- hour and maximum gpm limits after analyzing data made available mid

- testing. Thus, more energy factor ratings were produced than n ecessary for some water heaters. For example, water heater S

- NG

- 2 was tested under low, medium, and high usage draw patterns even though it currently qualifies for the high usage test, since it originally qualified for the medium usage test before DOE adju stments.

g This analysis excludes the change in energy factor for water heaters S

- E

- 4, S

- E

- 5, and S

- E

- 6 since their small storage volumes (greater than 2 and less than 20 gallons) limit them to point of use applications and cannot be appropriately tested u nder the current test procedure.18

Figure 5: Energy factor of storage water heaters under proposed test procedure as
p ercentage of current energy factor, as function of current energy factor

F igure 6: Energy factor of storage water heaters under proposed test procedure as
p ercentage of current energy factor, as function of applicable draw profile

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

0 0.5 1 1.5 2 2.5Energy factor under new test procedure aspercentage of energy factor under current test

Energy factor rating under current test procedure

Natural gas Oil Electric Heat pump Line of equivalence

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

0.0 1.0 2.0 3.0 4.0Energy factor under new test procedure aspercentage of energy factor under current test

Applicable draw profile under new test procedure

Natural gas Oil Electric Heat pump Line of equivalence

Point of use Low usage Medium usage High usage19

4.2. INSTANTANEOUS WATER HEATERS

The change in energy factor for instantaneous water heaters due to the differences between the current and proposed test procedures is evaluated for the six available instantaneous water heaters. As noted previously, one of the instantaneous water heaters tested (I-E-3) is outside of the scope of the current test method. However, since the current test method could be run on that unit without modification, and since the unit is covered by the proposed revised test method, DOE included that unit for comparison. Two of the three gas-fired instantaneous water heaters saw a slight increase in their measured energy factor under the proposed test procedure, while all thre e electric-powered instantaneous water heaters saw a decrease, as shown in Figure 7 . When isol ated by applicable draw pattern in Figure 8 the results are more easily assessed, as the point of use water heater category shows a clearer decrease in measured energy factor than the low, medium

, and high usage categories, which tend to instead stay relatively constant from the current to proposed test procedure.

Figure 7: Energy factor of instantaneous water heaters under proposed test procedure as
p ercentage of current energy factor, as function of current energy factor20

Figure 8: Energy factor of instantaneous water heaters under proposed test procedure as
p ercentage of current energy factor, as function of applicable draw profile21

5. EFFECTS OF PROPOSED TEST PROCEDURE ON DIFFERENT CATEGORIES OF WATER HEATER

Since DOE expects the proposed changes in the test method to likely affect different categories of water heaters in different ways, DOE is presenting the average change in first-hour, maximum gpm, and energy factor ratings separately by type, applicable draw profile, and energy source.

5 .1. STORAGE WATER HEATERS

Table 5 below shows the average change in measured first-hour rating of the twelve storage

wa ter heaters evaluated. The measured first-hour ratings for storage water heaters on average increased by 3%, with water heaters tested under the high usage draw pattern experiencing the
most significant increase in measured first-hour rating and water heaters tested under the low
usage draw pattern experiencing the most significant decrease.

Table 5: Averaged first-hour rating of storage water heaters under proposed test
p rocedure as percentage of current first-hour rating, categorized by energy source and applicable draw profile

The average change in measured energy factor for the twelve storage water heaters is shown in Ta ble 6 below

. On average, the measured energy factor of water heaters tested under the high
usage draw pattern increased by 8%, while water heaters tested under the medium and low usage dr aw patterns decreased by 4% and 1 1 % on average, respectively. Again, this is expected as the energy factor is correlated to the total volume drawn during the 24-hour simulated use test for storage water heaters.

Table 6: Averaged energy factor of storage water heaters under proposed test procedure as
p ercentage of current energy factor, categorized by energy source and applicable draw profile22

5.2. INSTANTANEOUS WATER HEATERS

Table 7 below shows the average change in the measured maximum gpm rating of instantaneous

wa ter heaters for different categories of applicable draw profile and energy source. The point of

use and low usage electric categories saw increases of 14 % a nd 13% on average for the

mea sured maximum gpm, respectively, while the medium and high usage natural gas categories

sa w increases in measured maximum gpm of 1 4 % and 9%, respectively.

Table 7: Averaged maximum gpm rating of instantaneous water heaters under proposed te st procedure as percentage of current maximum gpm rating, categorized by energy

sou rce and applicable draw profile

The average change in energy factor for instantaneous water heaters is shown in Table 8 below. The electric point of use, electric low usage, and natural gas medium usage categories experience decreases in energy factor of 23%, 4%, and 2% on average, respectively. The natural gas high
usage category experienced a 3% increase in its energy factor, on average.

Table 8: Averaged energy factor of instantaneous water heaters under proposed test
p rocedure as percentage of current energy factor, categorized by energy source and applicable draw profile23

6. VARIANCE IN ENERGY FACTOR RATINGS FOR WATER HEATERS UNDER DIFFERENT DRAW PROFI LES

The water heaters tested by DOE in this report were subject ed to at least one other draw profile that did not match its applicable draw pattern prescribed by the proposed test procedure based on the tested first hour rating (storage water heaters) or maximum gpm rating (instantaneous water he aters). As explained above, the additional draw profile(s) tested were the pattern(s) directly above and/or below the nominal usage pattern that the unit would qualify for. This allow ed DOE to evaluate how different 24-hour simulated use test draw patterns affect the performance of diff erent categories of water heaters. In this section, the variance in measured energy factor for

wa ter heaters tested under different draw profiles is observed for appropriate water heater

c ategories. These include water heater type, energy source, and applicable draw pattern.

6 .1. BY WATER HEATER TYPE
The observed water heater energy factor under the proposed test procedure is filtered by storage

wa ter heaters in Figure 9 and by instantaneous water heaters in Figure 11

. Additionally, Figure 10 shows the energy factor ratings of the storage heat pump water heater S- HP -1 under different draw profiles in a separate chart, since its energy factor is so much greater than normal heat
pump wa ter heaters that it would make trends observed in Figure 9 less obvious. From Figure 9 and Figure 10 below, the measured energy factor of storage water heaters (including heat pump water heater S- HP -1) increases as the draw profile moves from point of use through high usage. From Figure 11 , the measured energy factor of instantaneous water heaters appears to follow a sim ilar trend as storage water heaters, though potentially experiences a plateau from the low throug h high usage draw profiles.24

Figure 9 : Energy factor ratings of storage water heaters tested with different draw profiles (heat pump water heater S- HP -1 excluded)

Figure 10: Energy factor ratings of storage heat pump water heater S- HP

- 1 tested with different draw profiles 0 0.2 0.4 0.6 0.8 1 1.2

POU Low usage Medium usage High usageEnergy factor

Draw profile

S-NG-1 S-NG-2 S-NG-3 S-NG-4 S-NG-5 S-O-1 S-O-2

S-E-1 S-E-2 S-E-3 S-E-4 S-E-5 S-E-6 S-E-7

0 0.5 1 1.5 2 2.5 3

POU Low usage Med. usage High usageEnergy factor

Draw Profile

S-HP-125

Figure 11 : Energy factor ratings for instantaneous water heaters tested with different draw profiles

6.2. BY ENERGY SOURCE
Changes in the measured energy factor of water heaters were then filtered by energy source. Figure 12 below isolates the change in the measured energy factor by natural gas-powered water heaters, and shows an increase in the measured energy factor from low through high usage draw profiles, as expected. F igure 13 and Figure 14 filter by oil-fired and electric water heaters,

re spectively, and show a similar trend as natural gas-fired water heaters. h The same increasing trend is observed when isolating for the heat pump water heater S- HP -1, as shown previously in Figure 10 above.

h The oil

- fired water heater sample only contains storage water heaters since no oil

- fired instantaneous water heaters were tested.26

Figure 12 : Energy factor ratings for water heaters using natural gas as an energy source

Figure 13 : Energy factor ratings for water heaters using oil as an energy source27

Figure 14 : Energy factor ratings for water heaters using electricity as an energy source

6.3. BY APPLICABLE DRAW PROFILE
Lastly, changes in the measured energy factor for water heaters were filtered by applicable draw
pr ofile – that is, the specific draw profile that the water heater qualified for given its performance in the first-hour or maximum gpm rating test. For example, F igure 15 plots the five water heaters that qualified for the point of use draw profile, yet were also tested under low usage draw profile

c onditions. In this figure, all five water heaters see significant increases in their measured energy fa ctor when placed under the low usage draw profile. Figure 16 filters for water heaters that
qua lified for th e low usage test, showing a marginal increase from point of use to low usage and from low to medium usage. i In addition, the heat pump (S- HP -1) water heater was also tested at the high usage pattern and shows a significant increase from medium to high usage, as observed in Figure 9 shown previously. Figure 17 filters by medium usage, and shows five water heaters that experience relatively marginal gains in measured energy factor. Figure 18 filters by high usage, and shows an obvious increase in measured energy factor.

i Although the heat pump water heater S- HP -1 also qualified for the low usage draw profile, it is not included in Figure 16 since its energy factor ratings are so high that they would make trends observed for other water heaters less obvious. The energy factor ratings of the heat pump water heater at different draw profiles are instead available in Figure 9 above.28

Figure 15 : Energy factor ratings for water heaters testing for point of use draw profile

Figure 16 : Energy factor ratings for water heaters testing for low usage draw profile (heat
p ump water heater S- HP -1 excluded) 0 0.2 0.4 0.6 0.8 1 1.2

POU Low usage Med. usage High usageEnergy factor

Draw Profile

I-E-3 S-E-129

Figure 17 : Energy factor ratings for water heaters testing for medium usage draw profile

Figure 18 : Energy factor ratings for water heaters testing for high usage draw profile30

7. SUMMARY

This report provides a preliminary assessment of the impact of proposed additions and revisions
to t he current test procedure for residential water heaters. These additions and revisions also apply to light commercial water heaters, which are defined as a new category of water heater in the notice of proposed rulemaking. Specifically, the impacts analyzed for this report include:

 Impact of proposed test procedure revisions on measured first hour rating of storage

wa ter heaters, maximum gallon per minute of instantaneous water heaters, and energy factor of storage and instantaneous water heaters

 Effects of the proposed test procedure revisions on different categories of water heater

 Variance in measured energy factor ratings of units tested under different draw profiles
Twenty-one water heaters were tested under the proposed test procedure, including fifteen
stora ge and six instantaneous water heaters. The energy factor and first hour rating tests specified b y the current test procedure are not applicable for three small storage water heaters, labeled in this study as S-E-4, S-E-5, and S-E-6, and thus comparisons between their measured energy factors under the current test procedure and the proposed test procedure cannot be made.

F or storage water heaters, DOE found that the measured first-hour rating under the proposed test
pr ocedure varied between 87 and 1 30 % of the measured first-hour rating under the current test, with an a verage of 103%. The energy factor measured under the proposed test procedure as

c ompared to that measured under the current test procedure varied by 89 to 128 %, with an

a verage of 102%. For instantaneous water heaters, DOE found that the maximum gpm rating unde r the proposed test procedure varied between 109 and 11 7 % of the current rating, with an

a verage of 113 %. The energy factor measured by the proposed test procedure as compared to that measured under the current test procedure varied by 74 to 103 %, with an average of 91 %.
This report also analyzed effects of the proposed test procedure revisions on different categories of water heater. The type of water heater most affected by the change in test procedure as observed in this study was the instantaneous, electric, water heater that would be tested using the point of use draw pattern, which saw an average energy factor rating of 77% the current value. The majority of other water heaters had measured energy factor ratings of 90 to 110% of the

mea sured energy factor under the current test method.
Lastly, this report evaluated how water heaters assigned to their nominal draw profile behaved whe n subject to different draw profiles. It was found in all cases that as the total volume of water dr awn during the 24-hour simulated use test increased—that is, the draw profile increased from point of use through high usage—the measured energy factor of the water heater also increased. Diff erent categories of water heaters experienced steeper climbs in energy factor from one test to another, the greatest being storage water heaters from medium to high usage, and both storage and instantaneous water heaters from point of use to low usage.
DOE will continue to conduct additional tests in order to better understand how the proposed test procedure affects the measured first-hour, maximum gpm, and energy factor ratings as compared to the values measured under the current test.