Energy Conservation Program: Test Procedure for Consumer Water Heaters and Residential-Duty Commercial Water Heaters

Federal RegisterJan 11, 2022

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DEPARTMENT OF ENERGY

10 CFR Parts 429, 430, and 431

[EERE-2019-BT-TP-0032]

RIN 1904-AE77

Energy Conservation Program: Test Procedure for Consumer Water Heaters and Residential-Duty Commercial Water Heaters

AGENCY:

Office of Energy Efficiency and Renewable Energy, Department of Energy.

ACTION:

Notice of proposed rulemaking and request for comment.

SUMMARY:

The U.S. Department of Energy (DOE) proposes to amend the test procedure for consumer water heaters and residential-duty commercial water heaters to update the procedure to the latest versions of the industry standards that are incorporated by reference and to consider procedures that are included in a draft industry standard, which is not currently incorporated by reference. DOE also proposes to interpret the statutory definition of consumer water heater to cover larger capacity heat pump type units as commercial equipment and proposes several new definitions for water heaters that cannot be appropriately tested with the current DOE test procedure, along with test methods to test these products. DOE is seeking comment from interested parties on the proposals.

DATES:

Comments:

DOE will accept comments, data, and information regarding this notice of proposed rulemaking (NOPR) on or before March 14, 2022. See section V, “Public Participation,” for details.

Meeting:

DOE will hold a webinar on Tuesday, January 25, 2022, from 1:00 p.m. to 5:00 p.m. See section V, “Public Participation,” for webinar registration information, participant instructions, and information about the capabilities available to webinar participants.

ADDRESSES:

Interested persons are encouraged to submit comments using the Federal eRulemaking Portal at

www.regulations.gov.

Follow the instructions for submitting comments. Alternatively, interested persons may submit comments, identified by docket number EERE-2019-BT-TP-0032, by any of the following methods:

Federal eRulemaking Portal: www.regulations.gov.

Follow the instructions for submitting comments.

Email to: WaterHeaters2019TP0032@ee.doe.gov.

Include the docket number EERE-2019-BT-TP-0032 in the subject line of the message.

No telefacsimilies (faxes) will be accepted. For detailed instructions on submitting comments and additional information on this process, see section V of this document.

Although DOE has routinely accepted public comment submissions through a variety of mechanisms, including postal mail and hand delivery/courier, the Department has found it necessary to make temporary modifications to the comment submission process in light of the ongoing COVID-19 pandemic. DOE is currently suspending receipt of public comments via postal mail and hand delivery/courier, and instead, the Department is only accepting electronic submissions at this time. If a commenter finds that this change poses an undue hardship, please contact Appliance Standards Program staff at (202) 586-1445 to discuss the need for alternative arrangements. Once the COVID-19 pandemic health emergency is resolved, DOE anticipates resuming all of its regular options for public comment submission, including postal mail and hand delivery/courier.

Docket:

The docket, which includes

Federal Register

notices, public meeting attendee lists and transcripts (if a public meeting is held), comments, and other supporting documents/materials, is available for review at

www.regulations.gov.

All documents in the docket are listed in the

www.regulations.gov

index. However, some documents listed in the index, such as those containing information that is exempt from public disclosure, may not be publicly available.

The docket web page can be found at

www.regulations.gov/docket?D=EERE-2019-BT-TP-0032.

The docket web page contains instructions on how to access all documents, including public comments, in the docket. See section V for information on how to submit comments through

www.regulations.gov.

FOR FURTHER INFORMATION CONTACT:

Ms. Julia Hegarty, U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Building Technologies Office, EE-5B, 1000 Independence Avenue SW, Washington, DC 20585-0121. Telephone: (202) 597-6737. Email

ApplianceStandardsQuestions@ee.doe.gov.

Ms. Kristin Koernig, U.S. Department of Energy, Office of the General Counsel, GC-33, 1000 Independence Avenue SW, Washington, DC 20585-0121. Telephone: (202) 586-3593. Email:

kristin.koernig@hq.doe.gov.

For further information on how to submit a comment, review other public comments and the docket, or participate in a public meeting (if one is held), contact the Appliance and Equipment Standards Program staff at (202) 287-1445 or by email:

ApplianceStandardsQuestions@ee.doe.gov.

SUPPLEMENTARY INFORMATION:

DOE proposes to incorporate by reference the following industry standards into part 430:

American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 41.1-2020, (ASHRAE 41.1-2020), “Standard Methods for Temperature Measurement,” approved June 30, 2020.

American National Standards Institute (ANSI)/ASHRAE Standard 41.6-2014, (ASHRAE 41.6-2014), “Standard Method for Humidity Measurement,” ANSI approved July 3, 2014.

Copies of ASHRAE 41.1-2020 and ASHRAE 41.6-2014 can be obtained from the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., 1791 Tullie Circle NE, Atlanta, GA 30329, (800) 527-4723 or (404) 636-8400, or online at:

www.ashrae.org.

American Society for Testing and Materials International (ASTM) Standard D2156-09 (Reapproved 2018) (ASTM D2156-09 (RA 2018)), “Standard Test Method for Smoke Density in Flue Gases from Burning Distillate Fuels,” reapproved October 1, 2018.

ASTM Standard E97-1987 (ASTM E97-1987 (W1991)), “Standard Test Methods for Directional Reflectance Factor, 45-Deg 0-Deg, of Opaque Specimens by Broad-Band Filter Reflectometry,” approved January 1987, withdrawn 1991.

Copies of ASTM D2156-09 (RA 2018) and ASTM E97-1987 (W1991) can be obtained from the American Society for Testing and Materials International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959 or online at:

www.astm.org.

See section IV.M of this document for a further discussion of these industry standards.

Table of Contents

I. Authority and Background

A. Authority

B. Background

II. Synopsis of the Notice of Proposed Rulemaking

III. Discussion

A. Scope of Applicability

1. Definitions

B. Updates to Industry Standards

1. ASHRAE 41.1

2. ASHRAE 118.2

C. Test Procedure Requirements

1. Commercial Water Heater Draw Pattern

2. Terminology

3. Test Conditions

4. Mixing Valve

5. Mass Measurements

6. Very Small Draw Pattern Flow Rate

7. Low Temperature Water Heaters

8. Heat Pump Water Heater Heaters

9. Circulating Gas-Fired Water Heaters

10. Solar Water Heaters

11. Connected Water Heaters

12. Drain Down Test Method

13. Alternate Order 24-Hour Simulated-Use Test

14. Untested Provisions

D. Reporting

E. Test Procedure Costs and Harmonization

1. Test Procedure Costs and Impact

2. Harmonization With Industry Standards

F. Compliance Date and Waivers

IV. Procedural Issues and Regulatory Review

A. Review Under Executive Order 12866

B. Review Under the Regulatory Flexibility Act

1. Description of Reasons Why Action Is Being Considered

2. Objectives of, and Legal Basis for, Rule

3. Description and Estimate of Small Entities Regulated

4. Description and Estimate of Compliance Requirements

5. Duplication, Overlap, and Conflict With Other Rules and Regulations

6. Significant Alternatives to the Rule

C. Review Under the Paperwork Reduction Act of 1995

D. Review Under the National Environmental Policy Act of 1969

E. Review Under Executive Order 13132

F. Review Under Executive Order 12988

G. Review Under the Unfunded Mandates Reform Act of 1995

H. Review Under the Treasury and General Government Appropriations Act, 1999

I. Review Under Executive Order 12630

J. Review Under Treasury and General Government Appropriations Act, 2001

K. Review Under Executive Order 13211

L. Review Under Section 32 of the Federal Energy Administration Act of 1974

M. Description of Materials Incorporated by Reference

V. Public Participation

A. Participation in the Webinar

B. Submission of Comments

VI. Approval of the Office of the Secretary

I. Authority and Background

Consumer water heaters are included in the list of “covered products” for which DOE is authorized to establish and amend energy conservation standards and test procedures. (42 U.S.C. 6292(a)(4)) DOE's energy conservation standards and test procedure for consumer water heaters are currently prescribed at Title 10 of the Code of Federal Regulations (CFR), part 430, section 32(d), and 10 CFR part 430, subpart B, appendix E (appendix E). As discussed in this NOPR, residential-duty commercial water heaters, for which DOE is also authorized to establish and amend energy conservation standards and test procedures (42 U.S.C. 6311(1)(K)), must also be tested according to appendix E. 10 CFR 431.106(b)(1) (

See

42 U.S.C. 6295(e)(5)(H)). DOE's energy conservation standards for residential-duty commercial water heaters are currently prescribed at 10 CFR 431.110(b)(1). The following sections discuss DOE's authority to establish and amend test procedures for consumer water heaters and residential-duty commercial water heaters, as well as relevant background information regarding DOE's consideration of test procedures for these products and equipment.

A. Authority

The Energy Policy and Conservation Act, as amended (EPCA),

authorizes DOE to regulate the energy efficiency of a number of consumer products and certain industrial equipment. (42 U.S.C. 6291-6317, as codified) Title III, Part B

of EPCA established the Energy Conservation Program for Consumer Products Other Than Automobiles, which sets forth a variety of provisions designed to improve energy efficiency. (42 U.S.C. 6291-6309, as codified) These products include consumer water heaters, the subject of this document. (42 U.S.C. 6292(a)(4)) Title III, Part C

of EPCA, added by Public Law 95-619, Title IV, section 441(a), established the Energy Conservation Program for Certain Industrial Equipment, which again sets forth a variety of provisions designed to improve energy efficiency. (42 U.S.C. 6311-6317, as codified) This equipment includes commercial water heaters, which are also the subject of this document. (42 U.S.C. 6311(1)(k))

All references to EPCA in this document refer to the statute as amended through Energy Act of 2020, Public Law 116-260 (Dec. 27, 2020).

For editorial reasons, upon codification in the U.S. Code, Part B was redesignated Part A.

For editorial reasons, upon codification in the U.S. Code, Part C was redesignated Part A-1.

The energy conservation program under EPCA consists essentially of four parts: (1) Testing, (2) labeling, (3) the establishment of Federal energy conservation standards, and (4) certification and enforcement procedures. Relevant provisions of EPCA specifically include definitions (42 U.S.C. 6291; 42 U.S.C. 6311), test procedures (42 U.S.C. 6293; 42 U.S.C. 6314), labeling provisions (42 U.S.C. 6294; 42 U.S.C. 6315), energy conservation standards (42 U.S.C. 6295; 42 U.S.C. 6313), and the authority to require information and reports from manufacturers (42 U.S.C. 6296; 42 U.S.C. 6316).

The Federal testing requirements consist of test procedures that manufacturers of covered products and commercial equipment must use as the basis for: (1) Certifying to DOE that their products comply with the applicable energy conservation standards adopted pursuant to EPCA (42 U.S.C. 6295(s); 42 U.S.C. 6296; 42 U.S.C. 6316(a)-(b)), and (2) making representations about the efficiency of those products (42 U.S.C. 6293(c); 42 U.S.C. 6314(d)). Similarly, DOE must use these test procedures to determine whether the products comply with relevant standards promulgated under EPCA. (42 U.S.C. 6295(s))

Federal energy efficiency requirements for covered products and covered equipment established under EPCA generally supersede State laws and regulations concerning energy conservation testing, labeling, and standards. (42 U.S.C. 6297(a)-(c); 42 U.S.C. 6316(a)-(b)) However, DOE may grant waivers of Federal preemption in limited circumstances for particular State laws or regulations, in accordance with the procedures and other provisions of EPCA. (42 U.S.C. 6297(d); 42 U.S.C. 6316(a); 42 U.S.C. 6316(b)(2)(D))

Under 42 U.S.C. 6293, the statute sets forth the criteria and procedures DOE must follow when prescribing or amending test procedures for covered products. Specifically, EPCA requires that any test procedures prescribed or amended shall be reasonably designed to produce test results which measure energy efficiency, energy use, or estimated annual operating cost of a covered product during a representative average use cycle or period of use and shall not be unduly burdensome to conduct. (42 U.S.C. 6293(b)(3)) Under 42 U.S.C. 6314, the statute sets forth the criteria and procedures DOE must follow when prescribing or amending test procedures for covered equipment, reciting similar requirements at 42 U.S.C. 6314(a)(2).

In addition, the Energy Independence and Security Act of 2007 (EISA 2007) amended EPCA to require that DOE amend its test procedures for all covered consumer products to integrate measures of standby mode and off mode energy consumption. (42 U.S.C. 6295(gg)(2)(A)) Standby mode and off mode energy consumption must be incorporated into the overall energy efficiency, energy consumption, or other energy descriptor for each covered product unless the current test procedures already account for and incorporate standby and off mode energy consumption or such integration

is technically infeasible. (42 U.S.C. 6295(gg)(2)(A)(i)-(ii)) If an integrated test procedure is technically infeasible, DOE must prescribe a separate standby mode and off mode energy use test procedure for the covered product, if technically feasible. (42 U.S.C. 6295(gg)(2)(A)(ii)) Any such amendment must consider the most current versions of the International Electrotechnical Commission (IEC) Standard 62301

and IEC Standard 62087,

as applicable. (42 U.S.C. 6295(gg)(2)(A))

IEC 62301,

Household electrical appliances—Measurement of standby power

(Edition 2.0, 2011-01).

IEC 62087,

Methods of measurement for the power consumption of audio, video, and related equipment

(Edition 3.0, 2011-04).

The American Energy Manufacturing Technical Corrections Act (AEMTCA), Public Law 112-210, further amended EPCA to require that DOE establish a uniform efficiency descriptor and accompanying test methods to replace the energy factor (EF) metric for covered consumer water heaters and the thermal efficiency (TE) and standby loss (SL) metrics for commercial water-heating equipment

within one year of the enactment of AEMTCA. (42 U.S.C. 6295(e)(5)(B)-(C)) The uniform efficiency descriptor and accompanying test method were required to apply, to the maximum extent practicable, to all water-heating technologies in use at the time and to future water-heating technologies, but could exclude specific categories of covered water heaters that do not have residential uses, can be clearly described, and are effectively rated using the TE and SL descriptors. (42 U.S.C. 6295(e)(5)(F) and (H)) In addition, beginning one year after the date of publication of DOE's final rule establishing the uniform descriptor, the efficiency standards for covered water heaters were required to be denominated according to the uniform efficiency descriptor established in the final rule (42 U.S.C. 6295(e)(5)(D)); and for affected covered water heaters tested prior to the effective date of the test procedure final rule, DOE was required to develop a mathematical factor for converting the measurement of their energy efficiency from the EF, TE, and SL metrics to the new uniform energy descriptor. (42 U.S.C. 6295(e)(5)(E)(i)-(ii))

The initial thermal efficiency and standby loss test procedures for commercial water heating equipment (including residential-duty commercial water heaters) were added to EPCA by the Energy Policy Act of 1992 (EPACT 1992), Public Law 102-486, and corresponded to those referenced in the ASHRAE and Illuminating Engineering Society of North America (IESNA) Standard 90.1-1989 (

i.e.,

ASHRAE Standard 90.1-1989). (42 U.S.C. 6314(a)(4)(A)) DOE subsequently updated the commercial water heating equipment test procedures on two separate occasions—once in a direct final rule published on October 21, 2004, and again in a final rule published on May 16, 2012. These rules incorporated by reference certain sections of the latest versions of ANSI Standard Z21.10.3,

Gas Water Heaters, Volume III, Storage Water Heaters with Input Ratings Above 75,000 Btu Per Hour, Circulating and Instantaneous,

available at the time (

i.e.,

ANSI Z21.10.3-1998 and ANSI Z21.10.3-2011, respectively). 69 FR 61974, 61983 (Oct. 21, 2004) and 77 FR 28928, 28996 (May 16, 2012).

EPCA also requires that, at least once every 7 years, DOE evaluate test procedures for each type of covered product and covered equipment, including consumer water heaters and commercial water heaters that are the subject of this document, to determine whether amended test procedures would more accurately or fully comply with the requirements for the test procedures to not be unduly burdensome to conduct and be reasonably designed to produce test results that reflect energy efficiency, energy use, and estimated operating costs during a representative average use cycle (or additionally, period of use for consumer products). (42 U.S.C. 6293(b)(1)(A); 6314(a)(1))

If the Secretary determines, on her own behalf or in response to a petition by any interested person, that a test procedure should be prescribed or amended, the Secretary shall promptly publish in the

Federal Register

proposed test procedures and afford interested persons an opportunity to present oral and written data, views, and arguments with respect to such procedures. (42 U.S.C. 6293(b)(2); 42 U.S.C. 6314(b)) The comment period on a proposed rule to amend a test procedure shall be at least 60 days

and may not exceed 270 days. (42 U.S.C. 6293(b)(2)) In prescribing or amending a test procedure, the Secretary shall take into account such information as the Secretary determines relevant to such procedure, including technological developments relating to energy use or energy efficiency of the type (or class) of covered products involved. (42 U.S.C. 6293(b)(2)). If DOE determines that test procedure revisions are not appropriate, DOE must publish in the

Federal Register

its determination not to amend the test procedures. (42 U.S.C. 6293(b)(1)(A)(ii); 42 U.S.C. 6314(a)(1)(A)(ii)) DOE is publishing this NOPR in satisfaction of the 7-year review requirement specified in EPCA.

For covered equipment, if the Secretary determines that a test procedure amendment is warranted, the Secretary must publish proposed test procedures in the

Federal Register

, and afford interested persons an opportunity (of not less than 45 days' duration) to present oral and written data, views, and arguments on the proposed test procedures. (42 U.S.C. 6314(b))

B. Background

As stated previously in this document, DOE's current test procedure for consumer water heaters appears at appendix E.

Pursuant to the requirements of the AEMTCA amendments to EPCA discussed previously, DOE updated the consumer water heater test procedure through a final rule published on July 11, 2014 (July 2014 final rule). 79 FR 40542. The July 2014 final rule: Established a uniform energy descriptor (

i.e.,

uniform energy factor (UEF)) for all consumer water heaters and for commercial water heaters with consumer applications (

i.e.,

those commercial water heaters that met the newly established definition of a “residential-duty commercial water heater”); extended coverage to eliminate certain gaps in the previous version of the consumer water heater test procedure, including small-volume storage water heaters (

i.e.,

with storage volumes between 2 and 20 gallons), large volume water heaters (

i.e.,

greater than 100 gallons for gas-fired and oil-fired storage water heaters and greater than 120 gallons for electric storage water heaters), and electric instantaneous water heaters; updated the draw pattern from a single 24-hour simulated-use test draw pattern to include several different draw patterns that vary depending on equipment capacity as measured by the first-hour rating (FHR) or maximum gallons per minute (Max GPM) test; and updated the outlet water temperature test condition requirement. 79 FR 40542, 40545, 40548, 40551-40554 (July 11, 2014).

As indicated, the uniform energy descriptor and the consumer water heater test procedure apply to “residential-duty commercial water heaters,” which were initially defined in the July 2014 final rule and include commercial water heaters with consumer applications.

Id.

at 79 FR 40586; 10 CFR 431.106(b)(1) and 10 CFR 431.110(b). DOE later amended the definition of a “residential-duty commercial water heater” in a final rule published on November 10, 2016 (November 2016 final rule), to define such equipment as any gas-fired storage, oil-fired storage, or electric instantaneous commercial water heater that meets the following conditions: (1) For models requiring electricity, uses single-phase external power supply; (2) Is not designed to provide outlet hot water at temperatures greater than

180 °F; and (3) Does not meet any of the following criteria:

Water heater type

Indicator of non-residential application

Gas-fired Storage

Rated input >105 kBtu/h; Rated storage volume >120 gallons.

Oil-fired Storage

Rated input >140 kBtu/h; Rated storage volume >120 gallons.

Electric Instantaneous

Rated input >58.6 kW; Rated storage volume >2 gallons.

81 FR 79261, 79321-79322; 10 CFR 431.102.

In the November 2016 final rule DOE also, in relevant part, revised some of the definitions for consumer water heater product classes and removed others. Definitions for both “electric heat pump water heater” and “gas-fired heat pump water heater” were removed, and revisions were made to the definitions of “electric storage water heater” and “gas-fired storage water heater,” which made each sufficiently broad to cover electric heat pump water heaters and gas-fired heat pump water heaters, respectively. 81 FR 79261, 79320-79321 (Nov. 10, 2016). The November 2016 final rule also amended the definitions of “electric instantaneous water heater”, “gas-fired instantaneous water heater”, “oil-fired instantaneous water heater”, and “oil-fired storage water heater.”

Id.

On December 29, 2016, DOE published a final rule (December 2016 final rule) that denominated the efficiency standards for consumer water heaters and residential-duty commercial water heaters in terms of the uniform efficiency descriptor (

i.e.,

the UEF metric) and established mathematical conversion factors to translate the EF, TE, and SL metrics to the UEF metric. 81 FR 96204. The published conversion factors were applicable for converting test results for a period of one year after the publication of the December 2016 final rule as required by EPCA, as amended by AEMTCA. 42 U.S.C. 6295(e)(5)(E)(v)(II); 81 FR 96204, 96208 (Dec. 29, 2016). The conversion factors translating previously tested EF, TE, and SL values to converted UEF values were removed from 10 CFR 429.17 on December 29, 2017, at which time all rated UEF values were to be based on actual testing to the test procedure published in the July 2014 final rule (

i.e.,

to the UEF test procedure). 81 FR 96204, 96235.

Most recently, on April 16, 2020, DOE published in the

Federal Register

a request for information (April 2020 RFI) seeking comments on the existing DOE test procedure for consumer water heaters and residential-duty commercial water heaters. 85 FR 21104. The April 2020 RFI discussed a draft version of the ANSI/ASHRAE Standard 118.2, which was published in March 2019 (March 2019 ASHRAE Draft 118.2), which is very similar to the existing DOE test procedure of consumer water heaters and residential-duty commercial water heaters. 85 FR 21104, 21108-21110 (April 16, 2020).

In the April 2020 RFI, DOE requested comments, information, and data about a number of issues, including: (1) Differences between the March 2019 ASHRAE Draft 118.2 and the existing DOE test procedure; (2) test tolerances for supply water temperature, ambient temperature, relative humidity, voltage, and gas pressure; (3) the location of the instrumentation that measures water volume or mass; and (4) how to test certain types of consumer water heaters that cannot be easily tested to the existing DOE test procedure (

i.e.,

recirculating gas-fired instantaneous water heaters, water heaters that cannot deliver water at 125 °F ±5 °F, and water heaters with storage volumes greater than 2 gallons that cannot have their internal tank temperatures measured).

Id.

at 85 FR 21109-21114.

DOE received comments in response to the April 2020 RFI from the interested parties listed in Table I.1.

Table I.1—List of Commenters With Written Submissions in Response to the April 2020 RFI

Commenter(s)

Reference in this NOPR

Commenter type *

A.O. Smith Corporation

A.O. SMITH

Air-Conditioning, Heating, and Refrigeration Institute

AHRI

TA.

American Public Gas Association

APGA

TA.

Appliance Standards Awareness Project, American Council for an Energy-Efficient Economy, Consumer Federation of America, National Consumer Law Center, Natural Resources Defense Council, and Northeast Energy Efficiency Partnerships

Joint Advocates

AG.

Bradford White Corporation

BWC

California Energy Commission

CEC

State.

CSA Group

CSA

TL.

Edison Electric Institute

EEI

Keltech Inc

Keltech

M C

Northwest Energy Efficiency Alliance

NEEA

AG.

Pacific Gas and Electric Company, San Diego Gas and Electric, and Southern California Edison

CA IOUs

Rheem Manufacturing Company

Rheem

Rinnai America Corporation

Rinnai

Stone Mountain Technologies, Inc

SMTI

* AG: Advocacy Group; State: Government Organization; I: Individual; M: Manufacturer; TA: Trade Association; TL: Test Laboratory; U: Utility or Utility Trade Association.

A parenthetical reference at the end of a comment quotation or paraphrase provides the location of the item in the public record.

The parenthetical reference provides a reference for information located in the docket of DOE's rulemaking to develop test procedures for consumer water heaters and residential-duty commercial water heaters. (Docket No. EERE-2019-BT-TP-0032, which is maintained at:

www.regulations.gov/docket/EERE-2019-BT-TP-0032

). The references are arranged as follows: (Commenter name, comment docket ID number, page of that document).

II. Synopsis of the Notice of Proposed Rulemaking

In this NOPR, DOE proposes to update appendix E, and related sections of the CFR, as follows:

(1) Incorporate by reference current versions of industry standards referenced by the current and proposed DOE test procedures: ASHRAE 41.1, ASHRAE 41.6, the pending update to ASHRAE 118.2 (contingent on it being substantively the same as the current draft under review), ASTM D2156, and ASTM E97.

(2) Add definitions for “circulating water heater”, “low temperature water heater”, and “tabletop water heater”.

(3) Specify how a mixing valve should be installed when the water heater is designed to operate with one.

(4) Modify flow rate requirements during the FHR test for water heaters with a rated storage volume less than 20 gallons.

(5) Modify timing of the first measurement in each draw of the 24-hour simulated-use test.

(6) Clarify the determination of the first recovery period.

(7) Clarify the mass of water to be used to calculate recovery efficiency.

(8) Modify the terminology throughout appendix E to explicitly state “non-flow activated” and “flow-activated” water heater, where appropriate.

(9) Clarify the descriptions of defined measured values for the standby period measurements.

(10) Modify the test condition specifications and tolerances, including electric supply voltage tolerance, ambient temperature, ambient dry bulb temperature, ambient relative humidity, standard temperature and pressure definition, gas supply pressure, and manifold pressure.

(11) Add provisions to address gas-fired water heaters with measured fuel input rates that deviate from the certified input rate.

(12) Clarify provisions for calculating the volume or mass delivered.

(13) Add specifications for testing for the newly defined “low temperature water heaters”.

(14) Clarify testing requirements for the heat pump part of a split-system heat pump water heater.

(15) Define the use of a separate unfired hot water storage tank for testing water heaters designed to operate with a separately sold hot water storage tank.

(16) Clarify that any connection to an external network or control be disconnected during testing.

(17) Add procedures for estimating internal stored water temperature for water heater designs in which the internal tank temperature cannot be directly measured.

(18) Modify the provisions for untested water heater basic models within 10 CFR 429.70(g) to include electric instantaneous water heaters.

DOE's proposed actions are summarized in Table II.1 and compared to the current test procedure; the reason for the proposed change is also listed.

Table II.1—Summary of Changes in Proposed Test Procedure Relative to Current Test Procedure

Current DOE test procedure

Proposed test procedure

Attribution

References the 1986 (Reaffirmed 2006) version of ASHRAE 41.1 for methods for temperature measurement

References the updated 2020 version of ASHRAE 41.1

Industry TP Update to ASHRAE 41.1.

The 1982 version of ASHRAE 41.6 for methods for humidity measurement is referenced within the 1986 version of ASHRAE 41.1

References the 2014 version of ASHRAE 41.6, which is referenced by ASHRAE 41.1-2020

Industry TP Update to ASHRAE 41.6.

References the 2009 version of ASTM D2156 for testing smoke density in flue gases from burning distillate fuels

References the version of ASTM D2156 that was reaffirmed in 2018

Industry TP Update to ASTM D2156.

The 1987 version of ASTM E97 for testing directional reflectance factor, 45-deg 0-deg, of opaque specimens by broad-band filter reflectometry is referenced within ASTM D2156-09

References the 1987 version of ASTM E97, which is referenced by ASTM D2156-09 (2018)

Industry TP Update to ASTM E97.

Does not define a “circulating water heater” as used in 10 CFR 430.2

Adds a definition for “circulating water heater” to 10 CFR 430.2

To improve the representativeness of the test procedure.

Does not define a “tabletop water heater” as used as a product class distinction at 10 CFR 430.32(d)

Adds a definition for “tabletop water heater” to 10 CFR 430.2

Reinstate definition inadvertently removed by previous final rule.

Does not address how to configure a water heater for test when a mixing valve is required for proper operation

Specifies how a mixing valve should be installed when the water heater is designed to operate with one

To improve the repeatability of the test procedure.

Requires the flow rate during the FHR test to be 1.0 ±0.25 gpm (3.8 ±0.95 L/min) for water heaters with a rated storage volume less than 20 gallons

Requires the flow rate during the FHR test to be 1.5 ±0.25 gpm (3.8 ±0.95 L/min) for water heaters with a rated storage volume less than 20 gallons

To improve the representativeness of the test procedure and to align with the industry test procedure ASHRAE 118.2.

Does not address the situation in which the first recovery ends during a draw when testing to the 24-hour simulated-use test

Clarifies that the first recovery period will extend to the end of the draw in which the first recovery ended, and that if a second recovery initiates prior to the end of the draw, that the second recovery is part of the first recovery period as well

To improve the repeatability of the test procedure.

The recovery efficiency equation for storage-type water heaters refers to the mass of water removed from the start of the test to the end of the first recovery period

Clarifies that, for the calculation of recovery efficiency, the mass of water removed during the first recovery period includes water removed during all draws from the start of the test until the end of the first recovery period

To improve the repeatability of the test procedure.

Appendix E uses the phrases “storage-type” and “instantaneous-type” to refer to “non-flow activated” and “flow-activated” water heaters, respectively

Uses the terms “non-flow activated” and “flow-activated” water heater, where appropriate

Clarification.

The descriptions for Q

su,0

, Q

su,f

su,0

su,f

, τstby,1,

t,stby,1

, and

a,stby,1

only address when the standby period occurs between draw clusters 1 and 2

The descriptions for Q

su,0

, Q

su,f

su,0

su,f

, τstby,1,

t,stby,1

, and

a,stby,1

are generalized to refer to the section where the standby period is determined

Clarification.

Specifies that the first required measurement for each draw of the 24-hour simulated-use test is 5 seconds after the draw is initiated

Specifies that the first required measurement for each draw of the 24-hour simulated-use test is 15 seconds after the draw is initiated

Reduce burden.

Requires the electric supply voltage to be within ±1 percent of the rated voltage for the entire test

Requires the electric supply voltage to be within ±2 percent of the rated voltage beginning 5 seconds after the start of a recovery and ending 5 seconds before the end of a recovery

Reduce burden.

Requires maintaining ambient temperature for non-heat pump water heaters within a range of 67.5 °F ±2.5 °F

Requires maintaining the ambient temperature for non-heat pump water heaters within a range of 67.5 °F ±5 °F, and with an average of 67.5 °F ±2.5 °F

Reduce burden.

Requires maintaining the dry bulb temperature for heat pump water heaters within a range of 67.5 °F ±1 °F

Requires maintaining the dry bulb temperature for heat pump water heaters within a range of 67.5 °F ±5 °F, and with an average of 67.5 °F ±1 °F during recoveries and an average of 67.5 °F ±2.5 °F when not recovering

Reduce burden.

Requires maintaining the relative humidity for heat pump water heaters within a range of 50 percent ±2 percent

Requires maintaining the relative humidity for heat pump water heaters within a range of 50 percent ±5 percent, and at an average of 50 percent ±2 percent during recoveries

Reduce burden.

Requires that the heating value be corrected to a standard temperature and pressure, but does not state what temperature and pressure is standard or how to correct the heating value to the standard temperature and pressure

States that the standard temperature is 60 °F (15.6 °C) and the standard pressure is 30 inches of mercury column (101.6 kPa). Provides a method for converting heating value from the measured to the standard conditions

To improve the repeatability of the test procedure.

Requires that the manifold pressure be within ±10 percent of the manufacturer recommended value

Clarifies that the manifold pressure tolerance applies only to water heaters with a pressure regulator that can be adjusted. Requires that the manifold pressure be within the greater of ±10 percent of the manufacturer recommended value or ±0.2 inches water column

Reduce burden.

Does not specify the input rate at which the gas supply pressure tolerance is determined

Specifies that the gas supply pressure tolerance is to be maintained when operating at the maximum input rate

Clarification.

Does not contain procedures for modifying the orifice of a water heater that is not operating at the manufacturer specified input rate

Adds provisions regarding the modification of the orifice

To improve the repeatability of the test procedure.

Does not specify how to calculate the mass removed from the water heater when mass is calculated indirectly using density and volume measurements

Specifies how to calculate the mass of water indirectly using density and volume measurements

To improve the repeatability of the test procedure.

Does not accommodate testing of “low temperature water heaters” in appendix E

Adds a definition of “low temperature water heater” in 10 CFR 430.2 and requires low temperature water heaters to be tested to their maximum possible delivery temperature in appendix E

To improve the representativeness and repeatability of the test procedure.

Does not explicitly define the test conditions required for each part of a split-system heat pump water heater

Explicitly states that the heat pump part of a split-system heat pump water heater is tested at the dry bulb temperature and relative humidity conditions required for heat pump water heaters, and that the storage tank is tested at the ambient temperature and relative humidity conditions required for non-heat pump water heaters

To improve the repeatability of the test procedure.

Does not accommodate testing of water heaters that require a separately-sold hot water storage tank to properly operate

Requires water heaters designed to operate with a separately-sold hot water storage tank to use an 80-gallon unfired hot water storage tank for testing

To improve the representativeness of the test procedure.

Does not address water heaters with network connection capabilities

Explicitly states that any connection to an external network or control be disconnected during testing

To improve the repeatability of the test procedure.

Does not accommodate certain water heaters for which the mean tank temperature cannot be directly measured

Adds a “drain down” procedure to estimate the mean tank temperature for certain water heaters for which the mean tank temperature cannot be directly measured

To improve the representativeness of the test procedure.

10 CFR 429.70(g) does not allow untested electric instantaneous water heaters to be certified, but does allow untested electric storage water heaters to be certified

Extends the untested provisions within 10 CFR 429.70(g) to include electric instantaneous water heaters

Reduce burden.

Additionally, DOE proposes to interpret the statutory definition of consumer water heater to exclude certain larger capacity heat pump type units and that such units would be covered as commercial equipment.

DOE has tentatively determined that the proposed amendments described in section III of this NOPR would not significantly affect the measured efficiency of consumer and residential-duty commercial water heaters. Discussion of DOE's proposed actions are addressed in detail in section III of this NOPR.

III. Discussion

A. Scope of Applicability

This document covers those products that meet the definition of consumer “water heater,” as defined in the statute at 42 U.S.C. 6291(27), as codified at 10 CFR 430.2. This document also covers commercial water heating equipment with residential applications,

i.e.,

“residential-duty commercial water heater” (10 CFR 431.102).

1. Definitions

In the context of covered consumer products, EPCA defines “water heater” as a product which utilizes oil, gas, or electricity to heat potable water for use outside the heater upon demand, including—

(a) Storage type units which heat and store water at a thermostatically controlled temperature, including gas storage water heaters with an input of 75,000 Btu per hour or less, oil storage water heaters with an input of 105,000 Btu per hour or less, and electric storage water heaters with an input of 12 kilowatts or less;

(b) Instantaneous type units which heat water but contain no more than one gallon of water per 4,000 Btu per hour of input, including gas instantaneous water heaters with an input of 200,000 Btu per hour or less, oil instantaneous water heaters with an input of 210,000 Btu per hour or less, and electric instantaneous water heaters with an input of 12 kilowatts or less; and

(c) Heat pump type units, with a maximum current rating of 24 amperes at a voltage no greater than 250 volts, which are products designed to transfer thermal energy from one temperature level to a higher temperature level for the purpose of heating water, including all ancillary equipment such as fans, storage tanks, pumps, or controls necessary for the device to perform its function. (42 U.S.C. 6291(27); 10 CFR 430.2)

In addition, at 10 CFR 430.2, DOE defines several specific categories of consumer water heaters, as follows:

(1) “Electric instantaneous water heater” means a water heater that uses electricity as the energy source, has a nameplate input rating of 12 kW or less, and contains no more than one gallon of water per 4,000 Btu per hour of input.

(2) “Electric storage water heater” means a water heater that uses electricity as the energy source, has a nameplate input rating of 12 kW or less, and contains more than one gallon of water per 4,000 Btu per hour of input.

(3) “Gas-fired instantaneous water heater” means a water heater that uses gas as the main energy source, has a nameplate input rating less than 200,000 Btu/h, and contains no more than one gallon of water per 4,000 Btu per hour of input.

(4) “Gas-fired storage water heater” means a water heater that uses gas as the main energy source, has a nameplate input rating of 75,000 Btu/h or less, and contains more than one gallon of water per 4,000 Btu per hour of input.

(5) “Grid-enabled water heater” means an electric resistance water heater that—

(a) Has a rated storage tank volume of more than 75 gallons;

(b) Is manufactured on or after April 16, 2015;

(d) Bears a permanent label applied by the manufacturer that—

(i) Is made of material not adversely affected by water;

(ii) Is attached by means of non-water-soluble adhesive; and

(iii) Advises purchasers and end-users of the intended and appropriate use of the product with the following notice printed in 16.5 point Arial Narrow Bold font: “IMPORTANT INFORMATION: This water heater is intended only for use as part of an electric thermal storage or demand response program. It will not provide adequate hot water unless enrolled in such a program and activated by your utility company or another program operator. Confirm the availability of a program in your local area before purchasing or installing this product.”

(6) “Oil-fired instantaneous water heater” means a water heater that uses oil as the main energy source, has a nameplate input rating of 210,000 Btu/h or less, and contains no more than one gallon of water per 4,000 Btu per hour of input.

(7) “Oil-fired storage water heater” means a water heater that uses oil as the main energy source, has a nameplate input rating of 105,000 Btu/h or less, and contains more than one gallon of water per 4,000 Btu per hour of input.

The definition for “grid-enabled water heater” includes the term “activation lock,” which is defined to mean a control mechanism (either by a physical device directly on the water heater or a control system integrated into the water heater) that is locked by default and contains a physical, software, or digital communication that must be activated with an activation key to enable the product to operate at its designed specifications and capabilities and without which the activation of the product will provide not greater than 50 percent of the rated first-hour delivery of hot water certified by the manufacturer. 10 CFR 430.2. As specified in this definition, the control mechanism must be physically incorporated into the water heater or, if a control system, integrated into the water heater to qualify as an activation lock. DOE is aware of certain state programs that encourage water heaters to be equipped with communication ports that allow for demand-response communication between the water heater and the utility.

DOE notes that

presence of such a communication port, in and of itself, would not qualify as an activation lock for the purpose of classifying a water heater as a grid-enabled water heater.

On May 7, 2019, the State of Washington signed House Bill 1444, which amended the Revised Code of Washington (RCW) (

i.e.,

the statutory code in the State of Washington), Title 19, Chapter 19.260 (RCW 19.260). On January 6, 2020, the State of Washington amended the Washington Administrative Code (WAC) (

i.e.,

the regulatory code in the State of Washington), Title 194, Chapter 194-24 (WAC 194-24) (Washington January 2020 Amendment) to align with RCW 19.260. Similarly, the State of Oregon published a final rule (Oregon August 2020 final rule) on August 8, 2020, which amended the Oregon Administrative Rules (OAR), Chapter 330, Division 92 (OAR-330-092). The Washington House Bill 1444 and the Oregon August 2020 final rule established a definition for electric storage water heater (RCW 19.260.020(14); OAR-330-092-0010(10)), an effective date of January 1,

2021 in Washington and January 1, 2022 in Oregon (RCW 19.260.080(1); OAR-330-092-0015(17)), a requirement that electric storage water heaters must have a modular demand response communications port compliant with the March 2018 version of the ANSI/CTA-2045-A communication interface standard, or a standard determined to be equivalent (RCW 19.260.080(1)(a)-(b); OAR-330-092-0020(17)), and, in Oregon, must bear a label or marking on the products stating either “DR-ready: CTA-2045-A” or “DR-ready: CTA-2045-A and [equivalent DR system protocol]” (OAR-330-092-0045(17)).

In the April 2020 RFI, DOE requested comment on the definitions currently applicable to consumer water heaters. 85 FR 21104, 21108 (April 16, 2020). Sections III.A.1.a through III.A.1.e address specific issues either requested by DOE or submitted by commenters.

a. Electric Heat Pump Storage Water Heater

In the April 2020 RFI, DOE requested feedback on the need for creating a separate definition for “electric heat pump storage water heater,” similar to the definition in the March 2019 ASHRAE Draft 118.2, or whether the current DOE definitions in 10 CFR 430.2 for “electric storage water heater” and “water heater,” which include “heat pump type units,” would adequately cover such products for the purpose of performing the DOE test procedure. 85 FR 21104, 21110 (April 16, 2020). Rheem supported the creation of a separate definition for electric heat pump storage water heaters, specifically to clarify power rating limits and to include different design types. (Rheem, No. 14 at p. 3) Rinnai supported the inclusion of a definition for electric heat pump water heaters but not the creation of a separate product category. (Rinnai, No. 13 at p. 4) EEI stated that DOE should adopt the March 2019 ASHRAE Draft 118.2 definition for electric heat pump storage water heaters. (EEI, No. 8 at p. 3) On the other hand, BWC stated that the definition for “electric heat pump water heater” is adequate at this time. (BWC, No. 12 at p. 2) A.O. Smith stated that the introduction of the electric heat pump water heater definition from the March 2019 ASHRAE Draft 118.2 is unnecessary and will cause confusion due to the difference in scope, and that DOE's definitions for heat pump type units with additional clarification regarding maximum amperage and input power would be sufficient. (A.O. Smith, No. 20 at p. 2) AHRI stated that DOE should carefully review the entire heat pump water heater market, consider how each of the various designs should be characterized, and consider changes to the definitions, as necessary. (AHRI, No. 17 at p. 4) NEEA stated that no change to the definition is needed yet as the “heat pump type units” definition is adequate as written. (NEEA, No. 21 at p. 6) NEEA also requested that DOE clarify the boundary between residential and commercial heat pump water heaters for testing purposes and further stated that residential is implied to include input rates lower than 6 kW,

whereas commercial is implied to include input rates greater than 12 kW, such that the 6-12 kW range is ambiguous. (

Id.

at pp. 1-3)

Power equals amperage times voltage, so the definition of consumer heat pump type unit corresponds to a maximum power rating of 6,000 W, or 6 kW (24 A times 250 V equals 6,000 W).

DOE's consideration of the March 2019 ASHRAE Draft 118.2 “electric heat pump storage water heater” definition, the comments received in response to the April 2020 RFI, and a review of the market, lead DOE to revisit its prior application of the water heater definition in the context of heat pump type water heaters. DOE is re-evaluating these terms with additional consideration of the distinction between heat pump water heater consumer products and commercial products. More specifically, DOE proposes to clarify the application of the “heat pump type” provision in the EPCA definition of “water heater.” DOE proposes that the “heat pump type” provision specifies the criteria to distinguish consumer water heaters that incorporate heat pumps from commercial water heaters that incorporate heat pumps.

As noted, EPCA defines water heater to include “(A) storage type units which heat and store water at a thermostatically controlled temperature, including . . . electric storage water heaters with an input of 12 kilowatts or less; (B) instantaneous type units which heat water but contain no more than one gallon of water per 4,000 Btu per hour of input, including . . . electric instantaneous water heaters with an input of 12 kilowatts or less; and (C) heat pump type units, with a maximum current rating of 24 amperes at a voltage no greater than 250 volts, which are products designed to transfer thermal energy from one temperature level to a higher temperature level for the purpose of heating water, including all ancillary equipment such as fans, storage tanks, pumps, or controls necessary for the device to perform its function.” (42 U.S.C. 6291(27))

“Storage type units” and “instantaneous type units” are not exclusive of “heat pump type units.” Based on the “water heater” definition, an electric heat pump type unit could be covered under the water heater definition's description of storage type units (if it heats and stores water at a thermostatically controlled temperature with an input of 12 kilowatts or less) or instantaneous type unit (if it heats water and contains no more than one gallon of water per 4,000 Btu per hour of input and has an input of 12 kilowatts or less). EPCA is not explicit as to whether heat pump type units are considered a subcategory of storage type units and instantaneous type units.

The November 2016 final rule treated heat pump type units as a subcategory of the other two types of units listed in the definition of water heater. Specifically, DOE stated in the November 2016 final rule that a heat pump water heater with a total rated input of less than 12 kW would be a consumer water heater, as EPCA classifies electric water heaters with less than 12 kW rated electrical input as consumer water heaters. 81 FR 79261, 79301-79302 (Nov. 10, 2016). However, upon a review of EPCA and the water heater market, DOE has tentatively determined that the interpretation presented in the November 2016 final rule is not the best reading of EPCA.

The structure of the statutory definition of “water heater” in the Energy Conservation Program for Consumer Products in Part A of EPCA, lists each type of water heater at equal subparagraph designations. Therefore, when defining “water heater” for the purpose of determining whether a water heater is a consumer water heater, the energy use criteria specified for heat pump type units

is to be applied separately and distinctly from the criteria specified for the broader categorizations of storage type units

and instantaneous type units.

For heat pump type units EPCA specifies a maximum current rating of 24 amperes at a voltage no greater than 250 volts. (42 U.S.C. 6291(27)(C))

For storage type units EPCA specifies gas storage water heaters with an input of 75,000 Btu per hour or less, oil storage water heaters with an input of 105,000 Btu per hour or less, and electric storage water heaters with an input of 12 kilowatts or less. (42 U.S.C. 6291(27)(A))

For instantaneous type units EPCA specifies gas instantaneous water heaters with an input of 200,000 Btu per hour or less, oil instantaneous water heaters with an input of 210,000 Btu per hour or less, and electric instantaneous water heaters with an input of 12 kilowatts or less. (42 U.S.C. 6291(27)(B))

This separate consideration of heat pump type units when defining the scope of the consumer water heater definition is further supported by

considering the output capacities associated with the input limits specified for each type of unit. The electrical requirements for heat pump type water heaters (

i.e.,

less than or equal to 24 amperes (A) at 250 volts (V) or less) align with common electrical requirements for a residential electrical circuit.

EPCA's energy use criteria for heat pump type units corresponds to an input rate of 6 kW.

Whereas, DOE's interpretation in the November 2016 final rule additionally applies the 12 kW input rate limit to heat pump type units. A heat pump type unit with an input rate of 12 kW would have a heating capacity (

i.e.,

output capacity) of approximately 42 kW, which is 3.6 times the output heating capacity provided by the largest possible consumer electric storage type water heater (

i.e.,

11.8 kW).

While a heat pump type unit with a 12 kW input capacity could theoretically be designed and installed in a residential application, a water heating capacity (

i.e.,

output capacity) of 42 kW would far exceed the water heating demand of any residential installation.

In a safely designed home electrical circuit, a circuit breaker should only service outlets and/or devices that add up to 80 percent of the maximum current rating for the circuit breaker (

i.e.,

a 30 A circuit breaker should only service up to 24 A across all outlets and/or devices connected to that circuit breaker). Further, large appliances, such as water heaters, if installed on a dedicated circuit, should not exceed 80 percent of the circuit rating. See section 550.12(D) of the 2019 California Electrical Code:

www.nfpa.org/codes-and-standards/all-codes-and-standards/codes-and-standards/free-access?mode=view.

Power (in watts) is calculated as current (

i.e.,

amperage) multiplied by voltage. The EPCA criteria of 24 A and 250 V correspond to a power of 6,000 W (

i.e.,

24 × 250 = 6,000), or 6 kW.

A 12-kW electric resistance water heater with an assumed recovery efficiency of 98 percent would have an output heating capacity of 11.8 kW (

i.e.,

12 kW × 0.98 = 11.8 kW). Whereas, an electric heat pump type water heater with a 12 kW input capacity, with an assumed recovery efficiency of 350 percent, would have an output heating capacity of 42 kW (

i.e.,

12 kW × 3.5 = 42 kW), which is 3.6 times greater than the 11.8 kW output heating capacity of an electric resistance water heater with equivalent input capacity.

This tentative interpretation is supported by the current market. DOE reviewed manufacturers' product literature and found no electric heat pump water heaters marketed towards residential use that were designed to operate at greater than 24 A at 250 V.

This proposed interpretation of the “heat pump type” provision would define the scope of “water heater” for the purpose of Part A of EPCA. The interpretation would not be applicable in the context of determining product classes for water heaters. Any such consideration of product classes would be governed by 42 U.S.C. 6295(q). As stated previously, “storage type units” and “instantaneous type units” are not exclusive of “heat pump type units.” The criteria established in the statutory definition of water heater for each of these types of units in the definition of “water heater” excludes units with capacities that would be more appropriately addressed as commercial water heaters.

When considering the unit types included in the water heater definition (

i.e.,

“storage type,” “instantaneous type,” and “heat pump type”) as separate and distinct elements, the statutory definition of consumer water heater includes only those heat pump type units that have a maximum current rating of 24 A at a voltage no greater than 250 V. Heat pump type water heaters with an input capacity greater than the 24 A at 250 V do not meet the EPCA definition of a covered water heater. Instead, such units would be commercial water heaters,

i.e.,

if a heat pump type water heater has either an amperage greater than 24 A or a voltage greater than 250 V, under the definition it would be a commercial water heater.

EPCA defines covered equipment as certain types of industrial equipment, including storage water heaters and instantaneous water heaters. (42 U.S.C. 6311(1)(K)) EPCA defines “industrial equipment,” in relevant part, as “any article of equipment [. . .] which is not a “covered product” as defined in 42 U.S.C. 6291(a)(2). (42 U.S.C. 6311(2)(A)) In the context of covered equipment, EPCA defines “storage water heater” as a water heater that heats and stores water within the appliance at a thermostatically controlled temperature for delivery on demand. Such term does not include units with an input rating of 4,000 Btu per hour or more per gallon of stored water. (42 U.S.C. 6311(12)(A)) The term “instantaneous water heater” is defined in the context of covered equipment as a water heater that has an input rating of at least 4,000 Btu per hour per gallon of stored water. (42 U.S.C. 6311(12)(B)) Under these EPCA definitions, a heat pump type water heater that was not defined as a consumer water heater would be either a commercial storage water heater or a commercial instantaneous water heater, depending on the input rating.

DOE has tentatively determined that heat pump water heaters, which operate with a maximum current rating greater than 24 A or at a voltage greater than 250 V, are more appropriately covered as commercial water heaters than consumer water heaters.

As discussed in the November 2016 final rule, electric heat pump water heaters with greater than 24 A at 250 V and a total input rate less than or equal to 12kW would be covered by the energy conservation standards for consumer electric storage water heaters.

See

81 FR 79261, 79301-79302. (Nov. 10, 2016). These standards for consumer electric storage water heaters effectively require electric resistance technology at less than or equal to 55 gallons of rated storage volume or baseline

heat pump technology at greater than 55 gallons of rated storage volume. However, section 1.12.3 of the DOE test procedure at the time

only included heat pump water heaters which have “a maximum current rating of 24 amperes (including the compressor and all auxiliary equipment such as fans, pumps, controls, and, if on the same circuit, any resistive elements) for an input voltage of 250 volts or less.” Therefore, electric heat pump water heaters with greater than 24 A at 250 V were not considered in the analysis of the April 2010 final rule, and, as such, the electric storage water heater standards are not applicable to these heat pump water heaters. Under the proposed interpretation in this NOPR, electric heat pump water heaters with greater than 24 A at 250 V and a total input rate less than or equal to 12kW would be subject to the commercial water heater standards, which specify a maximum standby loss. 10 CFR 431.110(a). DOE notes that it has established a test procedure for commercial water heaters (10 CFR 431.106), and any representation made by a manufacturer as to the energy efficiency or energy use of a commercial water heater must be based on testing in accordance with the DOE test procedure, and such representation must fairly disclose the results of such testing. (42 U.S.C. 6314(d)(1))

The electric storage water heater energy conservation standards established by the April 2010 final rule set a minimum efficiency level that was attainable by all heat pump water heaters available at the time. Therefore, the standard did not eliminate any heat pump water heaters from the market.

At the time of the April 2010 final, rule, the DOE test procedure for consumer water heaters was last updated by a final rule published on July 20, 1998. 63 FR 38737.

In determining the input rate of a water heater with a heat pump component for the purpose of classifying such a water heater as either a consumer water heater or a commercial water heater, DOE would consider the total input rate, including all heat pump components and the resistive elements. As specified in the definition of “water heater” and “commercial heat pump water heater,” determination of the rated electric power input includes all ancillary

equipment. 10 CFR 430.2 and 10 CFR 431.102. Similarly, DOE would consider all heat pump components and resistive elements in determining voltage and amperage.

DOE reviewed the electric heat pump water heater market and found that several new configurations of heat pump water heaters have either become available or will soon become available on the market. Based its review of the market, DOE has identified these new configurations as electric storage water heaters that are heat pump type units.

In the present market, a consumer heat pump water heater typically consists of an air-source heat pump and a storage tank that are integrated together into one assembly. This “typical” consumer heat pump water heater uses electricity, operates around 240 volts, and has two 4,500-watt backup resistance elements within the storage tank that operate non-simultaneously. The new configurations that DOE identified include split-system heat pump water heaters (which consist of a separate heat pump and storage tank that are sold together), heat pump only models (which are sold without a storage tank but require being paired with one), “retrofit-ready” or “plug-in” heat pump water heaters (which are integrated heat pump and storage tank water heaters that can operate on a shared 120V/15A circuit and plugged into a standard 120 V receptacle (

i.e.,

wall outlet)), and ground- or water-source heat pump water heaters.

Split-system heat pump water heaters are currently available and used in residential applications; however, they are relatively uncommon when compared to typical integrated heat pump water heaters. Although split-system heat pump water heaters are more prevalent outside of the United States, they are produced by manufacturers that sell water heaters within the United States. As such, split-system water heaters may become more prevalent in the U.S. market in the future, and the DOE test procedure should adequately test these products. The current DOE test procedure covers split-system heat pump water heaters and the relevant proposed amendments are discussed in section III.C.8.b of this document. DOE has tentatively determined that split-system heat pump water heaters are covered by the current definitions of “electric storage water heater” and “heat pump type units.”

DOE has identified heat pump water heaters models that are sold with only the heat pump (heat pump only water heaters) and must be paired with an external storage tank in the field, with the specific tank characteristics depending on the hot water requirements of the installation (

i.e.,

the heat pump can be used with storage tanks of various storage volumes). Currently, these units are marketed only for commercial use. However, some models of these units have rated voltage and amperage values below the limits specified in the “heat pump type unit” consumer water heater definition. Further, DOE has identified models that will soon enter the market that are marketed for residential and light-commercial use. To the extent that a heat pump only water heater is covered by the definition of “heat pump type unit” consumer water heater, it would be subject to the DOE test procedure for consumer water heaters. DOE proposes to add a definition to cover heat pump only water heaters to 10 CFR 430.2. This definition is presented in section III.A.1.c of this document where products with a similar application are discussed. Test procedure amendments proposed in this document specific to heat pump only water heaters are discussed in section III.C.8.c of this NOPR.

DOE reviewed the plug-in (or “retro-fit ready”) heat pump water heater market described previously (integrated heat pump and storage tank water heaters that can operate on a 120V/15A circuit and plugged into a standard 120 V receptacle (

i.e.,

wall outlet)) and has initially found that these products are still under development and are not commercially available at this time. On December 23, 2019, NEEA published version 7.0 of its Advanced Water Heating Specification,

which includes an appendix that describes plug-in heat pump water heaters. As reported, these products are being designed as an integrated heat pump and storage tank for space-constrained installations (

e.g.,

small closets) and to operate on a shared 120V/15A circuit. Indications are that plug-in heat pump water heaters will be marketed for residential use, have input rates at or below the 12 kW threshold to be considered a consumer electric storage water heater, and have voltage and amperage levels below the 250 V and 24 A limits to be considered a “heat pump type unit.” Based on the initial information available, plug-in heat pump water heaters would be covered by either the current definition of “electric storage water heater” or “heat pump type units.” As plug-in heat pump water heaters are not currently available on the market, DOE is not proposing any changes to the test procedure specific to these products in this NOPR. DOE may reevaluate this tentative determination at such time as when these models enter the market.

Version 7.0 of NEEA's Advanced Water Heater Specification can be found at:

www.neea.org/img/documents/Advanced-Water-Heating-Specification.pdf.

DOE has also identified heat pump water heaters that use alternative heat sources (

e.g.,

water- or ground-source) that, although more commonly installed in commercial applications, do have residential applications and are at or below the 12kW limit to be considered a consumer “water heater.” Alternative source heat pump water heaters were not prevalent in the market at the time DOE established the current consumer water heater test procedure and therefore were not considered in the development of the current DOE test procedure. 79 FR 40542, 40566-40567 (July 11, 2014).

Significant changes and clarifications to the test setup and test conditions would be required to appropriately represent the various alternative source heat pump water heater components and installation requirements. The current test procedure for consumer water heaters incorporates draw patterns to represent an average period of use for the products subject to the test procedure. Section 5.4.1 of appendix E. Alternative source heat pump water heaters were not considered in the development of the current draw pattern requirements. Based on a current review of the market, these water heaters continue to have a small market share and indications are that they are predominantly used in commercial applications. DOE currently does not have data as to the use of such water heaters as installed. Absent such data, DOE is unable to develop and propose test procedure provisions that would be representative of such water heaters during an average period of use. To the extent there is no test procedure for such covered water heaters, they would not be subject to energy conservation standards. Because of the limited market share and unavailability of usage data, DOE has tentatively determined not to propose test procedures for these products.

Based on the forgoing discussion, DOE has tentatively determined that the current definitions of “heat pump type” and “electric storage water heaters” adequately cover the electric heat pump water heaters on the market that are representative of residential use, including “plug in” and alternative source heat pump water heaters, and that a separate definition for “electric heat pump water heaters” is not needed at this time. However, as discussed previously in this NOPR, DOE is

proposing to add a new definition to cover heat pump only water heaters.

b. Gas-Fired Heat Pump Storage Water Heater

In the April 2020 RFI, DOE requested feedback on whether a separate definition for “gas-fired heat pump storage water heater,” similar to the definition in the March 2019 ASHRAE Draft 118.2, was needed or whether the current DOE definitions in 10 CFR 430.2 for “gas-fired storage water heater” and “water heater,” which include “heat pump type units,” would adequately cover such products for the purpose of performing the DOE test procedure. 85 FR 21104, 21110 (April 16, 2020). AHRI, A.O. Smith, BWC, EEI, Rheem, Rinnai, and SMTI recommended that DOE add a separate definition for “gas-fired heat pump storage water heater.” (AHRI, No. 17 at p. 4; A.O. Smith, No. 20 at p. 2; BWC, No. 12 at p. 2; EEI, No. 8 at p. 3; Rheem, No. 14 at p. 3; Rinnai, No. 13 at p. 4; SMTI, No. 19 at p. 2) A.O. Smith further stated that the gas-fired storage water heater input capacity limit (less than or equal to 75,000 Btu/h) is not appropriate for defining a gas-fired heat pump storage water heater that is representative of residential applications. (A.O. Smith, No. 20 at p. 2) AHRI stated that a separate definition for “gas-fired heat pump water heater” is appropriate and that DOE had already established a definition for it as part of the July 2014 final rule. (AHRI, No. 17 at p. 4) However, CEC stated there is no need to add a definition for “gas-fired heat pump storage water heater” because the definition currently in 10 CFR 430.2 for “gas-fired storage water heater” and “water heater” includes “heat pump type units,” which adequately covers gas-fired heat pump storage water heaters. (CEC, No. 11 at p. 2) CEC argued that introducing the new definition as suggested under the March 2019 ASHRAE Draft 118.2 would indirectly limit the scope of heat pump water heaters standards by limiting the size of the gas-fired heat pump water heaters to be tested. (

Id.

) NEAA agreed that the current definitions for “gas-fired storage water heater” and “heat pump units” are adequate to cover gas-fired heat pump storage water heaters for purposes of testing, but the commenter noted there is value in creating a definition for market clarity. (NEEA, No. 21 at p. 6)

In the July 2014 final rule, DOE defined a “gas-fired heat pump water heater” as “a water heater that uses gas as the main energy source, has a nameplate input rating of 75,000 Btu/h (79 MJ/h) or less, has a maximum current rating of 24 amperes (including all auxiliary equipment such as fans, pumps, controls, and, if on the same circuit, any resistive elements) at an input voltage of no greater than 250 volts, has a rated storage volume not more than 120 gallons (450 liters), and is designed to transfer thermal energy from one temperature level to a higher temperature level to deliver water at a thermostatically controlled temperature less than or equal to 180 °F (82 °C).” 79 FR 40542, 40567 (July 11, 2014). DOE also stated that gas-fired heat pump water heaters are covered by the test procedure established in the July 2014 final rule.

Id.

at 79 FR 40549. The November 2016 final rule replaced this definition with the current definition of “gas-fired storage water heater.” 81 FR 79261, 79320-79321 (Nov. 10, 2016). The current definition of “water heater,” which includes “heat pump type units” was added in a final rule published on February 7, 1989. 54 FR 6062, 6075. DOE reasoned in the November 2016 final rule that, because the definition of “gas-fired heat pump water heater” is not used in DOE's test procedures or energy conservation standards for consumer waters, removing this definition will have no effect on the implementation of DOE's regulations. 81 FR 79261, 79287.

Currently, a water heater that uses gas as the main energy source, has a nameplate input rating of 75,000 Btu/h or less, and contains more than one gallon of water per 4,000 Btu per hour of input is a gas-fired storage water heater. 10 CFR 430.2. If the gas-fired storage water heater also has a heat pump with a maximum current rating of 24 amperes at a voltage no greater than 250 volts, is designed to transfer thermal energy from one temperature level to a higher temperature level for the purpose of heating water, including all ancillary equipment such as fans, storage tanks, pumps, or controls necessary for the device to perform its function, it would be a heat pump type unit. 10 CFR 430.2. This definition of heat pump type unit is not exclusive of gas-fired units.

The input rate of models currently in development for residential application are less than 20,000 Btu/h, which the March 2019 ASHRAE Draft 118.2 defines as the limit for gas-fired heat pump water heaters, and which is well below the 75,000 Btu/h limit in DOE's regulations. Gas-fired heat pump water heaters currently under design will likely have voltage and amperage requirements below the DOE “heat pump type unit” requirements, as electricity is not the main fuel source. Recognizing that the market for heat pump type units that are gas-fired is still developing, limiting coverage to less than 20,000 Btu/h (consistent with March 2019 ASHRAE Draft 118.2) would not accommodate the potential for future products designed for residential applications that may have input rates above 20,000 Btu/h. Therefore, DOE has tentatively determined that the definitions of “heat pump type” and “gas-fired storage water heaters” adequately cover the water heaters that are within the ASHRAE definition of “gas-fired heat pump water heaters,” and a separate DOE regulatory definition is not needed at this time. Further, as DOE stated in the July 2014 final rule, gas-fired heat pump water heaters are covered by the DOE test procedure established in that rule. 79 FR 40542, 40549 (July 11, 2014).

c. Gas-Fired Instantaneous Water Heater

As discussed previously in this document, a gas-fired instantaneous water heater is a water heater that uses gas as the main energy source, has a nameplate input rating less than 200,000 Btu/h, and contains no more than one gallon of water per 4,000 Btu per hour of input. 10 CFR 430.2. In the April 2020 RFI, DOE requested feedback on the typical application of a specific configuration of gas-fired instantaneous water heaters, commonly referred to as “circulating gas-fired instantaneous water heaters.” 85 FR 21104, 21113 (April 16, 2020). As explained in the April 2020 RFI, DOE has found that several manufacturers produce consumer gas-fired instantaneous water heaters that are designed to be used with a volume of stored water (usually in a tank, but sometimes in a recirculating hot water system of sufficient volume, such as a hydronic space heating or designated hot water system) in which the water heater does not provide hot water directly to fixtures, such as a faucet or shower head, but rather replenishes heat lost from the tank or system through hot water draws or standby losses by circulating water to and from the tank or other system.

Id.

These circulating gas-fired instantaneous water heaters are typically activated by an aquastat

installed in a storage tank that is sold separately or by an inlet water temperature sensor.

Id.

DOE further stated that while the products identified by DOE are within the statutory and regulatory definition of a consumer water heater as a covered product, the design and application of circulating gas-fired instantaneous water heaters makes testing to the consumer water

heater test procedure difficult, if not impossible, as these products are not capable of delivering water at the temperatures and flow rates specified in the UEF test method.

Id.

An “aquastat” is a temperature measuring device typically used to control the water temperature in a separate hot water storage tank.

In response to the April 2020 RFI, AHRI, APGA, Rheem, and Rinnai recommended generally that DOE amend the regulatory definitions of gas-fired instantaneous water heaters to exclude models designed exclusively for commercial use with input rates below the consumer water heater input rate limit

(i.e.,

≤200,000 Btu/h) and provided circulating gas-fired instantaneous water heaters as an example. (AHRI, No. 17 at p. 2; APGA, No. 16 at pp. 1-2; Rheem, No. 14 at p. 2; Rinnai, No. 13 at p. 2) A.O. Smith addressed circulating gas-fired water heaters specifically, stating that these models are produced at input rates both above and below the consumer water heater input rate cut-off for gas-fired instantaneous water heaters, and that all circulating water heaters, regardless of input rate, serve commercial applications; as such, they should be excluded from the consumer water heater regulations. (A.O. Smith, No. 20 at pp. 1-2) AHRI, Rheem, and Rinnai stated that these types of water heaters are sold into commercial building applications and should not be tested using a residential draw profile, which would not be applicable. (AHRI, No. 17 at p. 11; Rheem, No. 14 at p. 8; Rinnai, No. 13 at p. 10)

Currently, an enforcement policy

is in place addressing circulating water heaters. As provided in the enforcement policy, DOE will not seek civil penalties for the failure to properly certify covered products or the distribution in commerce by a manufacturer or private labeler of covered products that are not in compliance with an applicable energy conservation standard, if the violation occurs on or before December 31, 2021, with respect to an individual model of water heater that:

Enforcement policy for circulating water heaters is available at:

www.energy.gov/sites/prod/files/2019/09/f66/Enforcement%20Policy-CirculatingWH.92019.pdf.

• Meets the statutory definition of an instantaneous type of consumer water heater per 42 U.S.C. 6291(27);

• Does not have an operational scheme in which the burner or heating element initiates and terminates heating based on sensing flow;

• Has a water temperature sensor located at the inlet of the water heater or in a separate storage tank that is the primary operating temperature means of initiating and terminating heating;

• Must be used in combination with a recirculating pump and either a separate storage tank or water circulation loop in order to achieve the water flow and temperature conditions recommended in the manufacturer's installation and operation instructions;

• Is designed to provide outlet hot water at a thermostatically controlled temperature greater than 180 °F; and

• Meets the corresponding energy conservation standards in 10 CFR 431.110.

As provided in the enforcement policy, a water heater must first meet the statutory definition of an instantaneous type of consumer water heater per 42 U.S.C. 6291(27) in order to be a circulating water heater. Inherent to being a water heater per 42 U.S.C. 6291(27), a product must be a “consumer product.” DOE's authority under the Energy Conservation Program for Consumer Products Other Than Automobiles established by EPCA (42 U.S.C. 6291-6309) applies to “consumer products.” (

See

42 U.S.C. 6292)

In relevant part, 42 U.S.C. 6291(1) states that a “consumer product” means any article of a type which, to any significant extent, is distributed in commerce for personal use or consumption by individuals. Through an examination of product literature, DOE has found that circulating water heaters are predominately marketed for commercial applications. However, the input rates of many of the available models are below the maximum input rate of a consumer water heater and can therefore be suitable for residential applications. As such, DOE has tentatively determined that circulating water heaters are covered “consumer products.” Further, circulating water heaters operate similarly to the heat pump only water heaters discussed in section III.A.1.a, which DOE tentatively determined are marketed towards consumers and have residential applications (

e.g.,

they extract water from a storage tank, heat the water, and return the heated water to the storage tank). The circulating water heaters currently on the market circulate water at high flow rates (

e.g.,

greater than 10 gpm) and are, for the most part, designed to deliver water at a temperature greater than 180 °F. These characteristics suggest that the circulating water heaters on the market would not be appropriate for residential applications. However, when developing the test procedure currently in appendix E, DOE is required to develop a test procedure that applied, to the maximum extent practicable, to all water heating technologies in use and to future water heating technologies. (42 U.S.C. 6295(e)(5)(H)) As a circulating water heater could be designed to operate in a similar manner to other consumer water heaters (

i.e.,

heat pump only water heaters) and at conditions appropriate for residential applications, DOE is required to amend appendix E to address these products.

DOE proposes to add the definition described below for circulating water heaters to 10 CFR 430.2. The proposed definition also covers heat pump only water heaters which are discussed in section III.A.1.a in this NOPR. Test procedure amendments for circulating water heaters are discussed in section III.C.9 of this document.

DOE proposes to define “circulating water heater” at 10 CFR 430.2 as “an instantaneous or heat pump type water heater that does not have an operational scheme in which the burner, heating element, or compressor initiates and terminates heating based on sensing flow; has a water temperature sensor located at the inlet of the water heater or in a separate storage tank that is the primary means of initiating and terminating heating; and must be used in combination with a recirculating pump and either a separate storage tank or water circulation loop in order to achieve the water flow and temperature conditions recommended in the manufacturer's installation and operation instructions.”

With regard to the other gas-fired instantaneous water heaters referenced by commenters, DOE has also examined the market for gas-fired instantaneous water heaters with an emphasis on product lines with input rates both above and below the consumer and commercial input rate threshold of 200,000 Btu/h. The models with an input rate at or below the 200,000 Btu/h threshold could be used in consumer applications, are nearly indistinguishable from water heaters marketed and used in consumer applications, and are completely self-contained; that is, no other components would be required for these products to operate within a residence. As such, DOE has tentatively determined that these models continue to be considered “consumer products” and are subject to the test procedures and energy conservation standards for consumer gas-fired instantaneous water heaters.

DOE has also examined gas-fired water heaters with input rates of 200,000 Btu/h or less, containing less than one gallon of water per 4,000 Btu/h of input, and with rated storage volumes greater than 2 gallons. In the July 2014 final rule, storage volume requirements were removed from the definition of a “gas-fired instantaneous water heater.” 79 FR 40542, 40567 (July 11, 2014). In the December 2016 final

rule, DOE stated that definitions for consumer water heaters added to EPCA under the National Appliance Energy Conservation Act of 1987 (NAECA; Pub. L. 100-12 (March 17, 1987)), which amended EPCA, do not place any limitation on the storage volume of consumer water heaters. (42 U.S.C. 6291(27); 81 FR 96204, 96210 (Dec. 29, 2016)) DOE further stated that the energy conservation standards established by EPCA for consumer water heaters apply to all consumer water heaters regardless of storage volume. 81 FR 96204, 96210. DOE also acknowledged that its delay in issuing test procedures for such products, as well as statements it has made in the past, may have caused confusion about whether these products are covered by energy conservation standards for consumer water heaters, and that achieving compliance with the statutory standards immediately would be quite burdensome for industry.

Id.

at 81 FR 96211. As such, DOE stated that it will not enforce the statutory standards applicable to these products until some point after DOE finalizes a conversion factor and the converted standards applicable to those products.

Id.

DOE has tentatively determined that the interpretation presented in the December 2016 final rule for gas-fired instantaneous water heaters with storage volume greater than 2 gallons is still valid.

d. Tabletop Water Heaters

On January 17, 2001, DOE published a final rule (January 2001 final rule) that established definitions and created a separate product class for tabletop water heaters. 66 FR 4474. A “tabletop water heater,” was defined in the January 2001 final rule as a water heater in a rectangular box enclosure designed to slide into a kitchen countertop space with typical dimensions of 36 inches high, 25 inches deep, and 24 inches wide.

Id.

at 66 FR 4497. The definition for “tabletop water heater” was removed from appendix E as part of the July 2014 final rule and was inadvertently not added to 10 CFR 430.2. 79 FR 40542, 40567-40568 (July 11, 2014). However, energy conservation standards for tabletop water heaters are still specified at 10 CFR 430.32(d).

In the April 2020 RFI, DOE requested feedback on whether the previous definition for “tabletop water heater” is still appropriate, and whether such products should continue to be considered separately from other classes of consumer water heaters. 85 FR 21104, 21108 (April 16, 2020). AHRI, A.O. Smith, BWC, Rheem, and Rinnai commented that the definition for “tabletop water heater” is still appropriate and should remain as a separate product class. (AHRI, No. 17 at p. 3; A.O. Smith, No. 20 at p. 2; BWC, No. 12 at p. 2; Rheem, No. 14 at p. 2; Rinnai, No. 13 at p. 2) EEI suggested that the definition include a rated capacity of at least 20 gallons and exclude the phrases “rectangular box” and “designed to slide into a kitchen countertop space” to make the definition broader. (EEI, No. 8 at p. 3) Keltech stated that point-of-use (POU) units may benefit from being classified as a “tabletop water heater” and that a category should be created for POU water heaters that can be installed under a countertop. (Keltech, No. 7 at p. 1)

In the January 2001 final rule, DOE separated tabletop water heaters from the electric storage water heater product class “due to strict size limitations for these products.” 66 FR 4474, 4478 (Jan. 17, 2001). Tabletop water heaters are a unique type of water heater that are designed to fit into a countertop and provide a working surface in the installed location; as such, they are inherently size-constrained. DOE has tentatively determined that excluding the phrases “rectangular box” and “designed to slide into a kitchen countertop space” would make the tabletop water heater definition broader but would also remove the distinction of the key features that distinguish tabletop water heaters from electric storage water heaters (

i.e.,

the tabletop water heater product class addresses the very specific size limitations and location installations associated with these products). Further, the addition of a minimum rated storage volume of 20 gallons would define a scope of coverage that might not include the full volume range of water heaters in a rectangular box enclosure designed to slide into a kitchen countertop space. Therefore, DOE has tentatively determined not to add a minimum rated storage volume.

A POU water heater is, in general terms, a water heater that is located where the hot water is needed (

e.g.,

under a sink or counter). Water heaters that are installed under sinks or counters are typically small electric storage water heaters (30 gallons or less) or electric instantaneous water heaters. For small electric storage water heaters, these products are currently covered by the definition for electric storage water heater, which does not have storage volume requirements.

See

10 CFR 430.2. The test procedure for electric storage water heaters varies slightly depending on the delivery capacity of the water heater, which is a result of the first-hour rating test.

See

section 5.4.1 of appendix E. DOE has tentatively determined that POU or small electric storage water heaters are adequately covered by the current DOE test procedure when tested to the very small or low draw patterns. The same can be said for electric instantaneous water heaters, for which the test procedure also varies slightly depending on the delivery capacity of the water heater, which is a result of the Max GPM test.

See

section 5.4.1 of appendix E.

For the reasons discussed previously, DOE proposes to add the “tabletop water heater” definition that was removed from appendix E in the July 2014 final rule to 10 CFR 430.2.

e. Residential-Duty Commercial Water Heaters

In the April 2020 RFI, DOE requested comment on the definition for “residential-duty commercial water heater,” which defines a category of commercial water heaters that are subject to the consumer water heater test procedure. 85 FR 21104, 21108 (April 16, 2020). AHRI, A.O. Smith, Rheem, and Rinnai supported the current definition of “residential-duty commercial water heater” and had no recommended changes. (AHRI, No. 17 at p. 3; A.O. Smith, No. 20 at p. 2; Rinnai, No. 13 at p. 3; Rheem, No. 14 at p. 2) Keltech recommended adding the intended market for the water heater as another criteria for determining whether a water heater is a residential-duty commercial water heater and stated that if a water heater is not intended for sale in a consumer setting, it should not be held to consumer requirements. (Keltech, No. 7 at p. 1) DOE acknowledges that some water heaters, which are intended for commercial use, are covered by the residential-duty commercial water heater definition and tested and rated to the consumer water heater test procedure and residential-duty commercial water heater energy conservation standards. These water heaters have characteristics that are similar to water heaters with residential applications and, as such, under 42 U.S.C. 6295(e)(5)(F), cannot be excluded from being tested and rated using the consumer water heaters test procedure and residential-duty commercial water heater energy conservation standards. Further, DOE has tentatively determined that whether a product is marketed as commercial or residential may not always be indicative of the intended installation location. For example, water heaters intended for residential use are sometimes marketed as “commercial-grade” as a means to convey

reliability.

Therefore, DOE has tentatively determined not to amend the definition for “residential-duty commercial water heater.”

A water heater designed to be installed in commercial applications will typically be used more often and be subjected to environments that are harsher than would be experienced by a water heater designed to be installed in residential application. Therefore, a “commercial-grade” water heater could be considered more reliable, as it can operate longer in such an environment without malfunctioning.

B. Updates to Industry Standards

The current DOE test procedure in appendix E references the following industry standards:

• ASHRAE 41.1-1986 (Reaffirmed 2006), Standard Method for Temperature Measurement (ASHRAE 41.1-1986 (RA 2006)); and

• ASTM D2156-09, (ASTM D2156-09), Standard Test Method for Smoke Density in Flue Gases from Burning Distillate Fuels.

ASHRAE 41.1-1986 (RA 2006) was superseded by ASHRAE 41.1-2013 on January 30, 2013 (ASHRAE 41.1-2013). ASHRAE 41.1-2013 was superseded by ASHRAE 41.1-2020 on June 30, 2020. Updates to ASHRAE 41.1 are discussed in section III.B.1.

ASTM D2156-09 was reapproved without modification in 2018 (ASTM D2156-09 (RA 2018)). Therefore, DOE proposes to update the reference of ASTM D2156-09 to the most recent industry standard (

i.e.,

ASTM D2156-09 (RA 2018)). ASTM D2156-09 and ASTM D2156-09 (RA 2018) directly reference ASTM E97-1987 (W1991), which is necessary to perform the procedures within ASTM D216-09 and ASTM D2156-09 (RA 2018). Therefore, DOE also proposes to incorporate by reference ASTM E97-1987 (W1991).

ASHRAE maintains a published water heater test procedure titled, “ANSI/ASHRAE Standard 118.2-2006 (RA 2015), Method of Testing for Rating Residential Water Heaters” (ANSI/ASHRAE 118.2-2006 (RA 2015)). The ANSI/ASHRAE 118.2-2006 (RA 2015) test procedure is similar to the DOE test procedure that was in effect prior to the July 2014 final rule, although neither the former nor the current DOE consumer water heater test procedure reference ANSI/ASHRAE Standard 118.2-2006 (RA 2015). In March 2019, ASHRAE published the March 2019 ASHRAE Draft 118.2, the second public review draft of Board of Standards Review (BSR) ANSI/ASHRAE Standard 118.2-2006R, “Method of Testing for Rating Residential Water Heaters and Residential-Duty Commercial Water Heaters,” which DOE referenced in the April 2020 RFI. 85 FR 21104, 21109-21111 (April 16, 2020). In April 2021, ASHRAE published substantive changes to a previous public review draft

of BSR ANSI/ASHRAE Standard 118.2-2006R, “Method of Testing for Rating Residential Water Heaters and Residential-Duty Commercial Water Heaters.” (April 2021 ASHRAE Draft 118.2) The March 2019 ASHRAE Draft 118.2 and April 2021 ASHRAE Draft 118.2 are examined together in section III.B.2. Both the March 2019 ASHRAE Draft 118.2 and April 2021 ASHRAE Draft 118.2 are similar to the current DOE test procedure but include some differences throughout, some of which would result in test procedure results different from the current DOE test procedure.

The April 2021 ASHRAE Draft 118.2 shows only the proposed substantive changes to the March 2019 ASHRAE Draft 118.2. All sections not included in the April 2021 ASHRAE Draft 118.2 are as proposed in the March 2019 ASHRAE Draft 118.2 or have not been changed in a way that their content affects the results of the test procedure proposed in the March 2019 ASHRAE Draft 118.2.

As discussed previously in this document, DOE will adopt industry test standards as DOE test procedures for covered products and equipment, unless such methodology would be unduly burdensome to conduct or would not produce test results that reflect the energy efficiency, energy use, water use (as specified in EPCA) or estimated operating costs of that equipment during a representative average use cycle. 10 CFR part 430, subpart C, appendix A, Section 8(c). While DOE would only consider adopting through incorporation by reference (IBR) a finalized version of ASHRAE 118.2, DOE is interested in receiving comments on the merits of the draft in anticipation of such a possibility, or to consider incorporating aspects of the draft into a revised DOE test procedure. The differences between the March 2019 ASHRAE Draft 118.2, the April 2021 ASHRAE Draft 118.2, and the DOE test procedure are discussed in section III.B.2 of this NOPR.

1. ASHRAE 41.1

As stated previously, ASHRAE 41.1-1986 (RA 2006) was superseded by ASHRAE 41.1-2013 and ASHRAE 41.1-2013 was superseded by ASHRAE 41.1-2020. ASHRAE 41.1-2013 removed the aspirated wet bulb psychrometer descriptions and stated they would be included in the next revision to ASHRAE 41.6, “Standard Method for Humidity Measurement.” ASHRAE 41.6 was updated on July 3, 2014 and included the aspirated wet bulb psychrometer descriptions that were removed in ASHRAE 41.1-2013. ASHRAE 41.1-2013 also added uncertainty analysis for temperature measurements, information for thermistor-type devices, descriptions for thermopiles, and reorganized the standard to be consistent with other ASHRAE standards. ASHRAE 41.1-2020 added conditional steady-state test criteria and further updated the standard to meet ASHRAE's mandatory language requirements.

Section 3.2.1 of appendix E requires that temperature measurements be made in accordance with ASHRAE 41.1-1986 (RA 2006), and section 3.2.2 of appendix E provides accuracy and precision requirements for air dry bulb, air wet bulb, inlet and outlet water, and storage tank temperatures. Sections 5.2.2.1 and 5.3.2 of appendix E effectively require steady-state operation in which the flow-activated water heater is operating at the maximum input rate, is supplied with water at a temperature of 58 °F ±2 °F, and delivers water at a temperature of 125 °F ±5 °F.

DOE reviewed ASHRAE 41.1-1986 (RA 2006), ASHRAE 41.1-2013, and ASHRAE 41.1-2020 and found that the sections most relevant to appendix E are the temperature measurement sections (

i.e.,

sections 5 through 11 of ASHRAE 41.1-1986 (RA 2006), section 7 of ASHRAE 41.1-2013, and section 7 of ASHRAE 41.1-2020)

and the steady-state test criteria added in ASHRAE 41.1-2020. The information in the temperature measurement sections of the three versions of ASHRAE 41.1 examined does not vary significantly. The additional steady-state test criteria of ASHRAE 41.1-2020 varies significantly from and is more stringent than

the criteria specified in sections 5.2.2.1 and 5.3.2 of appendix E; however, the appendix E criteria supersedes those in ASHRAE 41.1-2020. DOE has tentatively determined that updating the reference of ASHRAE 41.1-1986 (RA 2006) to the most recent version of the industry standard (

i.e.,

ASHRAE 41.1-2020) would not have a significant effect on the test results, as the content of the relevant sections of the ASHRAE 41.1 standards have not changed significantly and the new

content published in ASHRAE 41.1-2020 is superseded by appendix E. As such, DOE proposes to update the reference of ASHRAE 41.1-1986 (RA 2006) to ASHRAE 41.1-2020. ASHRAE 41.1-2020 references ASHRAE 41.6-2014 and requires its use when measuring the wet bulb temperature. The wet bulb temperature is required when testing heat pump water heaters to appendix E and, therefore, DOE proposes to incorporate by reference ASHRAE 41.6-2014.

Sections 5 through 11 of ASHRAE 41.1-1986 (RA 2006) were combined into section 7 of ASHRAE 41.1-2013.

If adopted, section 5.5.3 of ASHRAE 41.1-2020 would be used to determine steady-state operation within sections 5.2.2.1 and 5.3.2 of appendix E. Using this criteria, a flow-activated water heater delivering water between 120 °F and 121 °F, which is within the current delivery temperature range of 125 °F ±5 °F, would not be considered in steady-state due to the difference in temperature between the average of the sample and the set point temperature.

2. ASHRAE 118.2

a. Scope

Section 2 of the March 2019 ASHRAE Draft 118.2 defines the scope of products covered by the industry test standard more narrowly than the definitions for consumer water heaters and relevant commercial water heater definitions contained in EPCA. For example, section 2 of the March 2019 ASHRAE Draft 118.2 limits the storage volume for storage-type water heaters to 120 gallons or less and limits the maximum delivery temperature to 180 °F (82 °C), whereas EPCA does not define limits on storage volume or maximum delivery temperature (42 U.S.C. 6291(27); 42 U.S.C. 6311(12)(A)-(B).

In the April 2020 RFI, DOE requested comment on whether the March 2019 ASHRAE Draft 118.2 test method could be applied to water heaters beyond the scope defined in the March 2019 ASHRAE Draft 118.2 to cover all water heaters included within the scope of DOE's definitions for consumer water heaters and residential-duty commercial water heaters. 85 FR 21104, 21110 (April 16, 2020). And if modifications to the March 2019 ASHRAE Draft 118.2 would be required, DOE requested comment on what those modifications should be.

Id.

CA IOUs and Rinnai expressed their understanding that the March 2019 ASHRAE Draft 118.2 applies to all water heaters within the current scope of DOE's test procedure. (CA IOUs, No. 18 at p. 3; Rinnai, No. 13 at p. 5) A.O. Smith stated that most aspects of the March 2019 ASHRAE Draft 118.2 could be applied to water heaters beyond the scope defined in section 2 of the March 2019 ASHRAE Draft 118.2 with similar characteristics. (A.O. Smith, No. 20 at p. 3) Rheem supported application of the March 2019 ASHRAE Draft 118.2 test method to cover a broader scope, including all water heaters within DOE's definitions of consumer water heaters. However, Rheem commented that modification may be required to address key differences, along with validation testing of any changes. (Rheem, No. 14 at pp. 3)

The April 2021 ASHRAE Draft 118.2 did not propose changes to the scope; therefore, section 2 of the April 2021 ASHRAE Draft 118.2 is the same as the March 2019 ASHRAE Draft 118.2. DOE has tentatively reached a similar conclusion as the commenters that the March 2019 ASHRAE Draft 118.2 and April 2021 ASHRAE Draft 118.2 could be applied to water heaters that are outside of the scope found in section 2 of the March 2019 ASHRAE Draft 118.2 and within the scope of DOE's current consumer water heater test procedure. As noted previously in this section, the March 2019 ASHRAE Draft 118.2 scope limits the maximum rated storage capacity at 120 gallons and the maximum delivery temperature at 180 °F; whereas the scope prescribed by EPCA and the relevant implementing regulations does not include these limits. Further, DOE has found through testing that models with rated storage volumes above 120 gallons or that can deliver water above 180 °F can be tested to DOE's consumer water heater test procedure. Given the similarities between the current DOE test procedure and the March 2019 ASHRAE Draft 118.2 and April 2021 ASHRAE Draft 118.2, such models could also be tested using the ASHRAE test standard. Therefore, DOE has tentatively determined that the test procedure presented in the March 2019 ASHRAE Draft 118.2 and the April 2021 ASHRAE Draft 118.2 could be used to test water heaters outside of the scope presented in section 2 of the March 2019 ASHRAE Draft 118.2.

b. Test Setup

Figures

Section 6 of the March 2019 ASHRAE Draft 118.2 includes new figures that provide greater detail illustrating how to set up a water heater for test. For example, a by-pass (purge) loop is added to the inlet water line in Figures 1 through 8. Additional figures include: A test set-up for a storage water heater with a side inlet water line and top outlet water line; a test set-up for an instantaneous water heater with connections on the top; the placement of a thermal break in the inlet water line (the thermal break is added to the test set-up to prevent heat from traveling up the inlet piping into the by-pass loop section, as discussed in the next subsection); and two configurations for the thermocouple tree if it needs to be installed through the outlet water line.

In the April 2020 RFI, DOE requested feedback on whether the figures in appendix E should be updated to include additional detail, including the detail provided in the figures in the March 2019 ASHRAE Draft 118.2. 85 FR 21104, 21110 (April 16, 2020). If thought to be necessary, DOE asked that commenters address whether the additional specificity provided in the figures could be too restrictive for the purpose of the DOE test procedure, or whether such specificity would be justified by improving reproducibility of test results.

Id.

AHRI, A.O. Smith, CA IOUs, CSA, NEEA, Rheem, and Rinnai recommended that the figures in appendix E be updated to include additional detail in alignment with ASHRAE 118.2. (AHRI, No. 17 at p. 5; A.O. Smith, No. 20 at p. 3; CA IOUS, No. 18 at p. 3; CSA, No. 10 at p. 3; NEEA, No. 21 at p. 6; Rheem, No. 14 at p. 4; Rinnai, No. 13 at p. 5) Rheem stated further that the figures in the March 2019 ASHRAE Draft 118.2 represent test set-up configurations that have been utilized by the AHRI contract laboratories and were also developed through a best practices effort to improve test consistency and repeatability across different labs. (Rheem, No. 14 at p. 4) However, A.O. Smith suggested that any updates to the figures in appendix E be used for reference only and not be required, in order to avoid being overly restrictive. (A.O. Smith, No. 20 at p. 3)

Upon further comparison of the figures within the March 2019 ASHRAE Draft 118.2 and appendix E, DOE found that the location in which the inlet temperature is measured in figures 2A, 2B, and 3 of the March 2019 ASHRAE Draft 118.2 is different than in the corresponding figures 2 and 3 within appendix E. In the March 2019 ASHRAE Draft 118.2, the inlet temperature is measured on the upstream side of the heat trap formed by the U-bend in the required piping, while in appendix E the inlet temperature measurement location is on the downstream side of the U-bend. All figures in the March 2019 ASHRAE Draft 118.2 have the inlet temperature location on the upstream side of the U-bend, while the figures in appendix E vary depending on the type of water heater being tested. Maintaining the same inlet temperature location for all water heater types would simplify the test setup as compared to the current requirements of appendix E. Further, given the short pipe distance between the upstream and downstream side of the U-bend (on the order of a few inches), it is unlikely that changing the location from the downstream side to the upstream side would result in a measurable difference in temperature.

However, DOE does not have adequate test data to fully understand the effect that changing the location of the inlet temperature measurement will have on test results and therefore is not proposing the use of the inlet temperature locations specified in the March 2019 ASHRAE Draft 118.2. DOE welcomes information or data that may demonstrate any impact of inlet temperature measurement location on energy efficiency results.

Thermal Break

Section 6 of the March 2019 ASHRAE Draft 118.2 includes new figures that provide greater detail illustrating how to set up a water heater for test. These additional figures include the installation location of a thermal break in the inlet water line. Figure 9 of the March 2019 ASHRAE Draft 118.2 shows the thermal break installed in greater detail than the other figures and provides more detail on the material properties of the thermal break. The thermal break is added to the test set-up to prevent heat from traveling up the inlet piping into the by-pass loop section. When purging before a draw, any heat that is transferred from the water heater through the inlet piping to the by-pass loop section would be lost, as the by-pass loop is replenished with cold supply water. The thermal break helps to prevent this heat loss.

In the April 2020 RFI, DOE requested feedback on whether a definition of “thermal break”

should be added to its consumer water heater test procedure. 85 FR 21104, 21110 (April 16, 2020). AHRI, A.O. Smith, BWC, CSA, Keltech, NEEA, Rheem, and Rinnai supported the addition of a definition for “thermal break” to the test procedure. (AHRI, No. 17 at p. 5; A.O. Smith, No. 20 at p. 3; BWC, No. 12 at p. 2; CSA, No. 10 at pp. 3; Keltech, No. 7 at p. 1; NEEA, No. 21 at p. 6; Rheem, No. 14 at p. 4; Rinnai, No. 13 at p. 5) However, CEC argued that there is no need to add the definition to the test procedure since the definition can be incorporated by referencing a finalized version of ASHRAE 118.2. (CEC, No. 11 at p. 2)

A “thermal break” is defined in the March 2019 ASHRAE Draft 118.2 as a nipple made of material that has thermal insulation properties (

e.g.,

plastics) to insulate the by-pass loop from the inlet piping. It should be able to withstand a pressure of 150 psi and a temperature of 150 °F.

In the April 2020 RFI, DOE requested feedback on the necessity of a thermal break if no by-pass or purge loop is included in the test set-up. 85 FR 21104, 21110 (April 16, 2020). AHRI, A.O. Smith, and Rinnai stated that a thermal break should be included in the test set-up regardless of whether there is a by-pass or purge loop. (AHRI, No. 17 at p. 5; A.O. Smith, No. 20 at p. 3; Rinnai, No. 13 at p. 5) CSA, NEEA, and Rheem stated that a thermal break is not needed if no by-pass or purge loop is present. (CSA, No. 10 at p. 4; NEEA, No. 21 at p. 6; Rheem, No. 14 at p. 4)

Thermal breaks are not typically installed in the field. Therefore, installation of a thermal break is not representative of an actual installation configuration. The purpose of a thermal break is to minimize unrepresentative effects of other parts of the test setup. A by-pass loop is a method test labs use to ensure inlet water temperatures are within the bounds of the test procedure (

i.e.,

within 58 °F ±2 °F by the first measurement of the draw, which occurs at either 15 or 5 seconds from the start of draw when testing to the first-hour rating or 24-hour simulated-use test, respectively), but its inclusion in the test setup can create a condition whereby a constant low temperature can remove energy from the water heater at a higher rate than would be removed in the field. Heat naturally travels through the inlet piping during standby, and the flow rates and inlet temperatures required by the test procedure do not always counteract this heating of the inlet piping before the required inlet temperature measurements are taken. The addition of a thermal break can help prevent these unrepresentative tank losses due to the by-pass loop by creating a barrier between the highly conductive piping materials. The inclusion of a thermal break in test setups that use a by-pass loop would likely result in test results that are more representative than a test setup with a by-pass loop and no thermal break. However, use of a by-pass loop is not the only possible test setup for meeting the test conditions within appendix E and it is unclear the effect that requiring a thermal break in test setups would have on the results from testing using a setup other than one employing a by-pass loop. Absent such information DOE is not proposing to require the use of a thermal break at this time. Therefore, DOE has tentatively determined that a definition for “thermal break” is not necessary to include, and DOE is not proposing one in this NOPR.

In the April 2020 RFI, DOE requested feedback on whether the maximum temperature the thermal break must be able to withstand would appropriately be set at 150 °F, as is set in the March 2019 ASHRAE Draft 118.2. 85 FR 21104, 21110 (April 16, 2020). AHRI, A.O. Smith, BWC, CSA, Rheem, and Rinnai commented that a temperature of at least 150 °F is an appropriate temperature for a thermal break to be able to withstand. (AHRI, No. 17 at p. 5; A.O. Smith, No. 20 at p. 3; BWC, No. 12 at p. 2; CSA, No. 10 at pp. 3-4; Rheem, No. 14 at p. 4; Rinnai, No. 13 at p. 5-6) AHRI and BWC further commented that a thermal break should be made of plastic or another material that is not thermally conductive. (AHRI, No. 17 at p. 5; BWC, No. 12 at p. 2) Keltech stated that thermal breaks should be able to withstand a maximum temperature of at least 200 °F, stating that 150 °F might pose a problem for water heaters capable of producing more than 125 °F. (Keltech, No. 7 at p. 1)

The thermal break is installed on the inlet water line, upstream of the thermocouple measuring the inlet water temperature. DOE examined its test data and found that, when water was not being drawn off, the maximum temperature measured by the thermocouple measuring the inlet water temperature never exceeded 100 °F. Therefore, a thermal break that is installed upstream of the thermocouple measuring the inlet water temperature would not experience water temperatures exceeding 100 °F. However, as stated previously, DOE is not proposing to require the use of a thermal break and, as such, does not need to propose the maximum temperature the thermal break must be able to withstand.

c. First-Hour Rating

Flow Rate

The April 2021 ASHRAE Draft 118.2 indicates that the flow rate for water heaters with rated storage volumes less than 20 gallons would be 1.5 ±0.25 gpm (5.7 ±0.95 L/min). DOE has identified consumer water heaters with storage volumes less than 20 gallons and with input rates near or at the maximum input rate specified at 10 CFR 430.2 (

i.e.,

water heaters with low volume and high input rate). Section 5.3.3, “First-Hour Rating Test” of appendix E requires that water heaters with a storage volume less than 20 gallons be tested at 1.0 ±0.25 gallons per minute (gpm) (3.8 ±0.95 liters (L)/minute (min)), as opposed to 3.0 ±0.25 gpm (11.4 ±0.95 L/min) required for water heaters with rated storage volumes greater than or equal to 20 gallons. Water heaters with low volume and high input rates can potentially operate indefinitely at the 3.0 ±0.25 gpm (11.4 ±0.95 L/min) flow rate. When tested as currently required by appendix E, such products would have a measured FHR around 60 gallons (227 L) and, therefore, would be required to use the medium draw pattern, although such models could be

used in applications similar to water heaters that are required to test using the high draw pattern (

e.g.,

flow-activated instantaneous water heaters with high input rates and storage water heaters with greater than 20 gallons stored water and high input ratesand/or volumes). As such, the current method of testing these products may not best represent how they are used in the field.

In the April 2020 RFI, DOE requested feedback on the consumer water heater test procedure with respect to testing the delivery capacity of non-flow activated water heaters with low volume and high input rate. 85 FR 21104, 21114 (April 16, 2020). If amendments were thought to be warranted, DOE requested comment on what method(s) would be appropriate for determining the delivery capacity of such models and what attributes can be used to distinguish these water heaters from non-flow activated water heaters more appropriately tested by the FHR test.

Id.

Rheem stated that there is a need to update the test procedure for testing delivery capacity of non-flow activated water heaters with low volume and high input rate. (Rheem, No. 14 at p. 9) DOE submitted a comment on this issue to the March 2019 ASHRAE Draft 118.2, and a solution was proposed in the April 2021 ASHRAE Draft 118.2 in which the flow rate for water heaters with rated storage volumes less than 20 gallons would be 1.5 ±0.25 gpm (5.7 ±0.95 L/min) instead of the 1.0 ±0.25 gpm (3.8 ±0.95 L/min) currently specified in the consumer water heater test procedure. This change would allow a water heater that can run continuously (

i.e.,

low volume and high input rate) to have a FHR that would correspond to the high draw pattern. Further, lower capacity water heaters would not be able to continuously deliver hot water at 1.5 gpm, which would result in them continuing to be rated in a lower draw pattern.

DOE tested three electric storage water heaters with rated storage volumes below 20 gallons to the current DOE FHR test (

i.e.,

1.0 ±0.25 gpm (3.8 ±0.95 L/min)) and a FHR test at a flow rate of 1.5 ±0.25 gpm (5.7 ±0.95 L/min). All three electric storage water heaters are rated in the very small draw pattern (

i.e.,

they have low input rates). The three electric storage water heaters were tested 4 times to each version of the FHR test (

i.e.,

8 tests per unit and 24 tests total). The results of the tests are shown in Table III.1.

Table III.1—Average First-Hour Rating Based on a Flow Rate of 1.0

gpm

and 1.5

gpm

Unit No.

Average

FHR at

1.0 gpm

(3.8 L/min)

(gallons)

Average

FHR at

1.5 gpm

(5.7 L/min)

(gallons)

Change

(%)

7.3

7.5

+3.4

6.4

6.2

−2.2

6.9

7.2

+4.7

As shown in Table III.1, changing the flow rate from 1.0 gpm to 1.5 gpm resulted in an average change in FHR between −2.2 percent and +4.7 percent. As the FHR rating did not increase above 10 gallons (

i.e.,

the threshold for determining whether to test to the very small or low draw patterns during the 24-hour simulated-use test) when tested at 1.5 gpm, the water heaters would continue to be tested to the very small draw pattern when tested to the 24-hour simulated-use test.

Based on the testing of the three models, changing the flow rate during the FHR test for water heaters with a rated storage volume less than 20 gallons from 1.0 ±0.25 gpm (3.8 ±0.95L/min) to 1.5 ±0.25 gpm (5.7 ±0.95 L/min) would have a relatively minimal impact on the FHR for water heaters with low input rates, and the resultant FHR and associated draw pattern for the 24-hour simulated-use test would still be representative of the expected use in the field. However, for water heaters with high input rates the change in flow rate could significantly increase the FHR and result in some models being tested and rated for UEF using a higher draw pattern, which would provide ratings that are more representative of their actual use. For these reasons, DOE is proposing to change the flow rate during the FHR test for water heaters with a rated storage volume less than 20 gallons from 1.0 ±0.25 gpm (3.8 ±0.95L/min) to 1.5 ±0.25 gpm (5.7 ±0.95 L/min). This proposed change is also consistent with the April 2021 ASHRAE Draft 118.2, and, in development of the final rule, DOE will consider the flow rate as finalized in the update to ASHRAE 118.2.

Initiation Criteria

The April 2021 ASHRAE Draft 118.2 includes additional criteria defining the start of the FHR test, as compared to DOE's test procedure. Section 5.3.3.3 of appendix E of the current DOE test procedure states that prior to the start of the FHR test, if the water heater is not operating (

i.e.,

heating water), initiate a draw until cut-in

(

i.e.,

when the water heater begins heating water). The draw is then terminated any time after cut-in, and the water heater is operated until cut-out.

Once the maximum mean tank temperature is observed after cut-out, the initial draw of the FHR test begins. Section 7.3.3.3 of the April 2021 ASHRAE Draft 118.2 specifies that the draw preceding the initial draw of the FHR test must proceed until the outlet temperature drops 15 °F below the maximum outlet temperature observed, or until the draw time limit

is reached. If the draw time limit is reached before the outlet temperature drops 15 °F below the maximum outlet temperature observed, then the main heating source of the water heater is shut off and the draw is continued until the outlet temperature has dropped 15 °F below the maximum outlet temperature. Requiring the outlet temperature to drop 15 °F below the maximum outlet temperature may provide a more consistent starting condition for the FHR test compared to the pre-conditioning method specified in the current DOE test procedure because draws of varying lengths can create different internal tank temperature profiles. Thus, the additional requirement to tie the length

of the initial draw to a specific outlet temperature, which in some cases would extend the draw length as compared to the current DOE test procedure, could increase the repeatability of the FHR test.

“Cut-in” is defined in section 1 of appendix E as “the time when or water temperature at which a water heater control or thermostat acts to increase the energy or fuel input to the heating elements, compressor, or burner.”

“Cut-out” is defined in section 1 of appendix E as “the time when or water temperature at which a water heater control or thermostat acts to reduce to a minimum the energy or fuel input to the heating elements, compressor, or burner.”

The draw time limit is the rated storage capacity divided by the flow rate times 1.2 (

i.e.,

for a 75-gallon water heater the draw time limit would be 30 minutes, or 75 gallons divided by 3 gpm times 1.2).

The March 2019 ASHRAE Draft 118.2 specified two criteria for terminating the water draw prior to the start of the FHR test: A 15 °F drop in outlet temperature from the maximum outlet temperature observed and a cut-in. The draft requirement for a cut-in was replaced with the draw time limit in the April 2021 ASHRAE Draft 118.2.

In the April 2020 RFI, DOE requested feedback on whether the addition of an outlet temperature drop criterion for terminating the water draw prior to the start of the FHR test within the March 2019 ASHRAE Draft 118.2 is appropriate and/or necessary. 85 FR 21104, 21109 (April 16, 2020). If an outlet temperature drop criterion is appropriate, DOE requested comment and data on whether 15 °F is sufficiently representative, given consumer expectation, or whether a different threshold should be considered.

Id.

DOE also requested information on any potential impact to the testing burden that would result from an outlet temperature drop criterion.

Id.

Further, DOE requested comment on how to address water heaters that would not meet both initiation criteria (

i.e.,

both a cut-in and an outlet temperature drop) due to the ability to continuously deliver hot water at the prescribed test conditions.

Id.

AHRI generally agreed that the 15 °F drop is sufficiently representative. However, AHRI stated there are oil-fired water heaters available that cannot achieve this temperature drop. AHRI recommended that additional review and testing be done to determine how to address water heaters that would not meet both initiation criteria (

i.e.,

the 15 °F drop in outlet water temperature and a cut-in). (AHRI, No. 17 at p. 4) A.O. Smith, BWC, NEEA, Keltech, Rheem, and Rinnai agreed with AHRI's statements. (A.O. Smith, No. 20 at p. 2; BWC, No. 12 at p. 3; Keltech, No. 7 at p. 1; NEEA, No. 21 at p. 5; Rheem, No. 14 at p. 2; Rinnai, No. 13 at p. 3) CSA stated that it is part of a working group for ASHRAE Draft 118.2 to address this issue. (CSA, No. 10 at p. 2) NEEA stated that for water heaters with enough output capacity to never drop 15 °F, the FHR test is not necessary, and the water heater should be tested to the Max GPM test, even if the water heater is not technically flow-activated. (NEEA, No. 21 at p. 5)

The combination of the 15 °F drop in outlet water temperature and the draw time limit criteria to the start of the FHR test would provide a more repeatable pre-FHR draw, as the criteria to end the draw would be explicitly stated (in contrast to the current test procedure, which allows for any length of pre-FHR test draw, as long as a cut-in occurs before the end of the draw). Because the pre-FHR test draw would be more repeatable, the available energy content of the tank at the start of the FHR test would be more consistent among different test runs. In both the current DOE test procedure and the procedure in the April 2021 ASHRAE Draft 118.2, the FHR test is initiated after a cut-out from the recovery that occurs due to the pre-FHR test draw. Therefore, in both cases, the water heater can be considered “fully heated” and to have similar internal energy content, although differences may be present due to the internal water temperature gradient throughout the tank. However, it is unclear how these differences in internal tank temperature will affect the test results. Absent information as to the impact of the differences in internal tank temperature on the test results, DOE is not proposing to amend appendix E to include the pre-FHR test conditioning proposed in the April 2021 ASHRAE Draft 118.2.

Additionally, in the April 2020 RFI, DOE raised concerns over high input rate water heaters that can heat water quicker than it is being drawn off. 85 FR 21104, 21113-21114 (April 16, 2020). The solution

presented in the April 2021 ASHRAE Draft 118.2 was the addition of a draw time limit, which eliminates the chances of an indefinite water draw. The procedure currently in appendix E

also would not allow an indefinite draw and, as stated previously, it is unclear the effect the draw time limit proposal would have on test results. Therefore, DOE is not proposing to include the draw time limit within appendix E.

The draw time limit solution was the result of the working group in which CSA stated it was a part of. (CSA, No. 10 at p. 2)

Appendix E requires that the pre-FHR test draw be terminated after the water heater initiates a recovery.

DOE agrees in principle with NEEA that the Max GPM test may provide a representative value of delivery capacity and could be used to determine the appropriate draw pattern of a water heater with a sufficiently high input rate and low storage volume, despite not being flow-activated. However, it is unclear at this time how these types of non-flow activated water heaters could be separated from other non-flow activated water heaters that are appropriately tested with the FHR test and would be inappropriately tested with the Max GPM test.

Minimum Outlet Temperature

Section 7.3.3.3 of the March 2019 ASHRAE Draft 118.2 and section 7.3.3.4 of the April 2021 ASHRAE Draft 118.2 include additional criteria regarding water draws during the FHR test, as compared to the current DOE test procedure. The FHR test required in section 5.3.3 of appendix E specifies a series of water draws over the course of one hour. After each water draw is initiated, the draw is terminated when the outlet water temperature decreases 15 °F from the maximum outlet water temperature measured during the draw. For example, if after initiating a water draw, the outlet water temperature reaches a maximum temperature of 125 °F, the water draw would continue until the outlet water temperature drops to 110 °F, at which time the water draw would be terminated. Section 7.3.3.4 of the April 2021 ASHRAE Draft 118.2 specifies that water draws during the FHR test terminate if either: (1) The outlet water temperature decreases 15 °F from the maximum outlet water temperature measured during the draw, or (2) the outlet water temperature decreases to 105 °F, regardless of the maximum outlet water temperature measured during the draw. Setting a minimum temperature threshold of 105 °F would reflect that in practice because consumers would likely stop drawing water when it gets below 105 °F, as the water would no longer be considered “hot.”

In the April 2020 RFI, DOE requested feedback on whether the addition of a minimum outlet temperature as a criterion for terminating draws during the FHR test is appropriate and/or necessary. 85 FR 21104, 21109 (April 16, 2020). If a minimum outlet temperature criterion is appropriate, DOE requested comment and data on whether 105 °F would be sufficiently representative given consumer expectation, or whether a different threshold should be considered.

Id.

DOE also requested information on any potential impact this minimum outlet temperature may have on testing burden.

Id.

BWC and NEEA supported the minimum outlet temperature of 105 °F for terminating draws of the FHR test. (BWC, No. 12 at p. 2; NEEA, No. 21 at p. 5) Rheem supported a minimum outlet temperature, but suggested a 100 °F limit would be more appropriate and would better represent usable hot water temperatures, especially when considering electric water heaters used for point-of-use, such as handwashing applications. (Rheem, No. 14 at p. 3)

AHRI and Rinnai stated that a 15 °F drop in outlet temperature or 105 °F minimum outlet temperature, whichever is higher, would be sufficiently representative. (AHRI, No. 17 at p. 4; Rinnai, No. 13 at p. 4) A.O. Smith and Rheem suggested more testing and investigation are necessary before any decisions are made. (A.O. Smith, No. 20 at p. 2; Rheem, No. 14 at p. 3) CSA stated that, when testing to the March 2019 ASHRAE Draft 118.2, all draws would be terminated at 105 °F regardless of outlet temperature, but stated that this can potentially create a bias for conducting the procedure at the higher end of 125 ±5 °F tolerance. CSA further stated that some water heaters start stacking

after the first draw, resulting in the outlet temperature going above 130 °F during the FHR test, and questioned how that would affect the overall FHR and draw pattern bin. (CSA, No. 10 at p. 2)

“Stacking” refers to when a storage water heater has hot water within the storage tank that is well above the temperature that is typically stored, which can result from successive short duration draws in a short amount of time. During typical operation, a draw removes hot water from the top of the storage tank, and the removed water is replaced with cold water that enters near the bottom the tank. The thermostat that controls the burner or element operation is also located near the bottom of the tank. Repeated short-duration draws result in multiple “bursts” of cold water entering the bottom of the tank; however, because the draws are short-duration, the total amount of water drawn is relatively small, and the temperature at the top of the tank may remain “hot” at the target setpoint. These short bursts of cold water entering near the thermostat may trigger a cut-in, and the water heater will begin heating despite the temperature at the top of the tank still being hot at the target setpoint. As the already-hot tank is being heated further, the temperature within the tank increases above the temperature that the water heater typical operates.

Based on a review of existing test data, the 105 °F outlet temperature criteria would affect only a small number of tests, if any. The test currently requires that the draw be terminated after a 15 °F drop in outlet temperature, and the outlet temperature is required to be between 120 °F and 130 °F when setting the thermostat. Therefore, the outlet temperature is unlikely to be below 105 °F during the test, as most draws should terminate before that point. The maximum outlet temperature of the draw would have to be below 120 °F for the 105 °F criteria to be triggered. As a result, DOE understands CSA's comment that all draws will be terminated at 105 °F, if tested to ASHRAE Draft 118.2, to be incorrect. Section 7.3.3.4 of the April 2021 ASHRAE Draft 118.2 includes a statement that requires the draw be terminated at 105 °F or when the outlet temperature is 15 °F below the maximum outlet temperature measured during the draw, “whichever is higher.” Therefore, if the maximum outlet temperature of a draw was 125 °F, for example, then the draw would end after a 15 °F drop, or once the outlet water temperature is 110 °F, which is higher than 105 °F. Also, Rheem's suggestion of a 100 °F limit to address handwashing water heaters would not be appropriate for water heaters generally and would be more appropriately addressed as part of development of a method to appropriately test such water heaters (

see

section III.C.7). DOE is not proposing to add the 105 °F minimum outlet temperature criteria to the FHR test draw termination criteria, as further test data is needed to assess the effect on the FHR test results.

Scaling of the Last Draw Volume

Section 5.3.3.3 of appendix E includes a provision for the FHR test requiring that if the final draw is not initiated prior to one hour from the start of the test, then a final draw is imposed at the elapsed time of one hour. In this situation, calculations presented in section 6.1 of appendix E are used to determine the volume drawn during the final draw for purposes of calculating FHR. The volume of the final draw is scaled based on the temperature of the water delivered during the final draw as compared to the temperature of the water delivered during the previous draw. The calculated final draw volume is added to the total volume drawn during the prior draws to determine the FHR. The April 2021 ASHRAE Draft 118.2 does not include a final draw volume scaling calculation for the case in which a draw is not in progress at one hour from the start of the test and a final draw is imposed at the elapsed time of one hour. Instead, the April 2021 ASHRAE Draft 118.2 method calculates FHR as the sum of the volume of hot water delivered without any scaling of the final draw.

The methodology for conducting the FHR test, and in particular the issue of whether to scale the final draw, was considered by DOE in a final rule that was published on May 11, 1998 (May 1998 final rule). In the May 1998 final rule, DOE determined that scaling the final draw volume based on the outlet water temperature was appropriate and was included to adjust the volume of the last draw to account for the lower heat content of the last draw compared to the earlier draws with fully heated water. 63 FR 25996, 26004-26005 (May 11, 1998).

In the April 2020 RFI, DOE requested comment on whether the scaling of final draw volume should be maintained as part of the FHR calculation, in the case that a draw is not initiated prior to one hour from the start of the test but is imposed at that time before the water has been heated to the specified temperature to initiate the draw. 85 FR 21104, 21111 (April 16, 2020). DOE further requested feedback on the effect that removing the scaling of the final draw volume would have on the rated FHR, draw pattern, and rated UEF values of the various types of non-flow activated water heaters that are tested to the FHR test.

Id.

In response, AHRI, A.O. Smith, BWC, Rheem, Rinnai, and SMTI suggested that DOE remove the final draw volume scaling calculation, which would be consistent with the March 2019 ASHRAE Draft 118.2. (AHRI, No. 17 at p. 6; A.O. Smith, No. 20 at p. 3; BWC, No. 12 at p. 3; Rheem, No. 14 at p. 5; Rinnai, No. 13 at p. 6; SMTI, No. 19 at p. 3) AHRI, A.O. Smith, Rinnai, and Rheem further stated that removing the final draw volume scaling would have minimal impact on the rated FHR, draw pattern, and rated UEF values. (AHRI, No. 17 at p. 6; A.O. Smith, No. 20 at p. 3; Rinnai, No. 13 at p. 6; Rheem, No. 14 at p. 5) CSA stated that the current final draw volume scaling method should be maintained and that a water heater delivering water at 106 °F should not be equal to a water heater delivering water at 110 °F. According to CSA, the outlet water temperatures would most likely be tempered by the end user, and the water heater delivering 110 °F water would supply more tempered water than a water heater delivering 106 °F, even though the volume of the last draw, as measured, would be roughly the same. CSA stated further that removing the scaling of the final draw volume could possibly move water heaters to the next highest draw pattern. (CSA, No. 10 at p. 5)

The scaling of the final draw accounts for the possible lower heat content of the last draw as compared to earlier draws. The test procedure specifies a constant flow rate throughout testing. The flow rate is fixed, and, as water is drawn, the water temperature decreases. In practice, water used by the consumer is typically at a lower temperature than is delivered by the water heater (

i.e.,

water drawn from the water heater is mixed with water from the cold tap). The flow rate of water delivered to the consumer by a faucet or showerhead is fixed by the faucet or showerhead. As the heat content of the water delivered by the water heater decreases, the flow rate of water from the water heater is increased to maintain the temperature of the mixed water delivered by the faucet

or showerhead (

i.e.,

in practice, as water temperature decreases, the flow rate of water from the water heater is increased). Thus, DOE has tentatively determined that scaling the final draw volume based on outlet temperature is more representative of the actual use in the field.

Further, removing the scaling of the final draw volume would result in many FHR values having to be recertified as many models have the final draw imposed at the one-hour mark (only those models that initiated their final draw prior to 1 hour would not be affected). Because the change is to the calculation of FHR only, retesting would not be needed unless the resulting FHR value required a new 24-hour simulated-use test due to a change in the applicable draw pattern bin (

e.g.,

if the FHR increases such that a model moves from the medium to the high draw pattern). DOE agrees with commenters that most models would not require a new 24-hour simulated-use test. However, any retesting would be a burden on manufacturers and, as stated previously, removing the scaling provisions would result in a less representative test.

Removing or amending the scaling of the final draw volume would change the FHR value, which could change the required draw pattern to use for the simulated-use test, as defined in section 5.4.1 of appendix E. The current draw pattern thresholds were determined based on the current final draw scaling methodology, and are therefore representative of actual use only when used with FHR values based on the current final draw scaling methodology. Removing or amending the scaling of the final draw volume could require adjusting the draw pattern thresholds to ensure that the applicable draw patterns (based on FHR value thresholds) remain representative of actual use.

The FHR metric is a method to compare the amount of usable water that a water heater can produce in a given amount of time. As long as the metric is applied consistently throughout the market, the consumer can use it to make comparisons among different models. Removing the scaling of the final draw volume may increase test burden on some manufacturers while resulting in a less representative test, and could require an update to the draw pattern thresholds. As described, changes to the draw pattern threshold could result in water heaters being classified in a lower draw pattern than they are currently, and it is uncertain as to the extent the reclassification would result in a test procedure that is representative for such models. Therefore, DOE has tentatively determined not to remove or amend the scaling of the final draw volume.

In response to the April 2020 RFI, SMTI stated that, if the scaling of the final draw volume was maintained, the equation should be amended to use the inlet water temperature as opposed to the minimum outlet temperature of the previous draw. According to SMTI, this change would make the overall calculation more representative of the energy availability in the final draw. (SMTI, No. 19 at p. 3-4) However, while basing the scaling calculation on inlet water temperature as opposed to outlet water temperature would be more representative of the energy availability in the tank, it would not be more representative of the energy availability in the final draw. The energy that is useful to the consumer is based on the energy of water delivered at a temperature at or above the consumer's desired temperature. The consumer's desired temperature is approximated in the FHR test by the minimum delivery temperature of the draw and not the inlet water temperature. Therefore, DOE has tentatively determined that scaling the final draw volume based on the inlet water temperature would result in a less representative test and a metric that could mislead the consumer as to how much hot water they actually have available. Further, the change suggested by SMTI to base the scaling of the final draw volume on inlet water temperature would result in a FHR value that is higher than under the current DOE test procedure, but to a lesser degree than if the temperature scaling were removed. As stated, DOE has tentatively determined that amending scaling of the final draw volume to use the inlet water temperature as opposed to the minimum outlet water temperature would result in a less representative test and, therefore, DOE is not proposing this change.

d. 24-Hour Simulated-Use Test

Initiation Criteria

Similar to the initiation criteria discussed in section III.B.2.c for the FHR test, section 7.4.2 of the April 2021 ASHRAE Draft 118.2 includes criteria for a pre-24-hour simulated-use test draw, which ends after either the outlet temperature drops by 15 °F or the draw time limit is reached. Section 5.4.2 of appendix E currently requires that the water heater sit idle for 1 hour prior to the start of the 24-hour simulated-use test; during which time no water is drawn from the unit and no energy is input to the main heating elements, heat pump compressor, and/or burners. Appendix E provides no instruction on how to condition the tank prior to this one hour. However, as discussed in section III.B.2.c, it is unclear how the outlet temperature drop criteria and the draw time limit will affect the internal tank temperature at the start of the 24-hour simulated-use test and how this difference in internal tank temperatures will affect the test results. Therefore, DOE is not proposing to amend appendix E to include the preconditioning proposed in the April 2021 ASHRAE Draft 118.2. DOE welcomes data that provide information regarding the impact of the preconditioning provisions in the April 2021 ASHRAE Draft 118.2 on the UEF result.

Recovery Efficiency

Section 8.3.2 of the March 2019 ASHRAE Draft 118.2 includes language specifying that, when the first recovery of the 24-hour simulated-use test ends during a draw, the first recovery period extends until the end of that draw. The first recovery period is used in section 8.3.2 of the March 2019 ASHRAE Draft 118.2 and section 6.3.2 of appendix E to calculate recovery efficiency. DOE's test procedure does not explicitly address how to calculate recovery efficiency if the first recovery period ends during a draw. A recovery period is defined in section 1 of appendix E as “the time when the main burner of a storage water heater is raising the temperature of the stored water.” Each of the parameters in the recovery efficiency equation are recorded from the “beginning of the test to the end of the first recovery period following the first draw.” The DOE test procedure does not explicitly state whether values are recorded at the end of the recovery period that ends after the initiation of the first draw, or at the end of a recovery period that occurs after the end of the first draw.

In the April 2020 RFI, DOE requested feedback on whether additional specification should be added to appendix E addressing the first recovery period ending during a draw. 85 FR 21104, 21111 (April 16, 2020). DOE further requested that if extending the first recovery period to the end of the draw is thought to be appropriate, whether the test procedure should also address the situation where a second recovery is initiated prior to the ending of the draw.

Id.

DOE also requested how to appropriately find the maximum mean tank temperature after cut-out following the recovery period.

Id.

AHRI, A.O. Smith, CSA, Rheem, and Rinnai generally supported adding a specification in appendix E to address the first recovery period ending during a draw. (AHRI, No. 17 at p. 7; A.O.

Smith, No. 20 at p. 3; CSA, No. 10 at p. 5; Rheem, No. 14 at p. 5; Rinnai, No. 13 at p. 7) AHRI, A.O. Smith, Rheem, and Rinnai supported extending the first recovery period to the end of the draw to include all water heater activity up to and including the end of the draw. (AHRI, No. 17 at p. 7; A.O. Smith, No. 20 at p. 3; Rheem, No. 14 at p. 5; Rinnai, No. 13 at p. 7) AHRI and Rheem recommended that the maximum mean tank temperature just after the first cut-out be used. (AHRI, No. 17 at p. 7; Rheem, No. 14 at p. 5) CSA recommended that for the other scenarios outlined by DOE, testing should be conducted to determine the proper procedure. (CSA, No. 10 at p. 5) No comments were received directly addressing the issue of when a second recovery starts prior to the end of the draw in which the first recovery ended.

The situation in which a recovery ends during a draw likely occurs during draws with a low enough flow rate that the water heater can heat water more quickly than the draw is removing. The energy used for the recovery efficiency calculation includes energy used to heat water and auxiliary energy; therefore, the energy associated with the first recovery period should represent the entire draw to capture all energy use. Commenters generally agreed that the maximum mean tank temperature measured after the recovery should be right after cut-out (

i.e.,

in the middle of the draw). After cut-out, as the draw continues, the mean tank temperature will drop as heated water is replaced by cold inlet water; therefore, the mean tank temperature immediately after cut-out will be the maximum observed. As such, DOE proposes to explicitly provide that when the first recovery ends during a draw, the first recovery period is extended to the end of the draw and the mean tank temperature measured immediately after cut-out is used as the maximum mean tank temperature value in the recovery efficiency calculation.

On January 31, 2020, DOE published a Notice of Decision and Order

(Decision and Order) by which a test procedure waiver for certain basic models was granted to address the issue of a second recovery initiating during the draw during which the first recovery ended. 85 FR 5648. The Decision and Order prescribes an alternate test procedure that extends the first recovery period to include both the first and second recoveries.

Id.

at 85 FR 5652. In the context of the Decision and Order, DOE determined that the consideration of delivered water mass and inlet and outlet temperatures until the end of the draw is appropriately representative, and, therefore, the entire energy used from both recoveries is included.

Id.

at 85 FR 5651-5652.

Notice of Decision and Order in response to BWC petition for waiver is available at:

www.regulations.gov/document?D=EERE-2019-BT-WAV-0020-0008.

In the April 2020 RFI, DOE requested feedback on whether the equation for recovery efficiency for water heaters with a rated storage volume greater than or equal to 2 gallons (7.6 L) should be updated to address when the recovery period lasts for more than one draw. 85 FR 21104, 21111 (April 16, 2020). CSA, EEI, NEEA, Rheem, and Rinnai recommended that DOE update the recovery efficiency calculation to account for the period extending beyond one draw to increase clarity. (CSA, No. 10 at p. 5; EEI, No. 8 at p. 4; NEEA, No. 21 at p. 6; Rheem, No. 14 at p. 6; Rinnai, No. 13 at p. 7) This change was presented in the March 2019 ASHRAE Draft 118.2 and is in the Notice of Decision and Order. 85 FR 5648, 5652 (Jan. 31, 2020). Consistent with the published Notice of Decision and Order and as supported by commenters, DOE proposes to update the recovery efficiency equation to specify accounting for the mass of water drawn for all draws initiated during the recovery period. As such, DOE is proposing to amend appendix E consistent with the alternate test procedure in the Decision and Order.

Standby Period

Appendix E includes a standby

period measured between the first and second draw clusters,

during which data is recorded that is used to calculate the standby heat loss coefficient. See section 5.4.2 of appendix E. Sections 7.4.2.1 and 7.4.2.2 of the March 2019 ASHRAE Draft 118.2 and sections 7.4.3.1 and 7.4.3.2 of the April 2021 ASHRAE Draft 118.2 add a condition that the standby period data can be recorded between the first and second draw clusters only if the time between the observed maximum mean tank temperatures after cut-out following the first draw cluster to the start of the second draw cluster is greater than or equal to 6 hours. Otherwise, the standby period data would be recorded after the last draw of the test. This condition would provide a sufficiently long standby period to determine standby loss, which might make this calculation more repeatable and the results more representative of standby losses experienced in an average period of use. However, this might also cause the test to extend beyond a 24-hour duration.

“Standby” is defined in section 1.12 of appendix E as “the time, in hours, during which water is not being withdrawn from the water heater.”

A “draw cluster” is defined in section 1 of appendix E as “a collection of water draws initiated during the 24-hour simulated-use test during which no successive draws are separated by more than 2 hours.” There are two draw clusters in the very small draw pattern and three draw clusters in the low, medium, and high draw patterns.

In the April 2020 RFI, DOE requested feedback on whether it should consider the addition of a minimum standby period length of 6 hours for use in the standby loss calculations, and on the appropriateness of recording this data after the final draw cluster when less than 6 hours of standby time occur between the first and second draw clusters. 85 FR 21104, 21110 (April 16, 2020). BWC stated that DOE should adopt a minimum standby period length of 6 hours for use in the standby loss calculation. (BWC, No. 12 at p. 3) NEEA stated that DOE should reduce the standby period to 4 hours, as it believed the increased burden to require a 6-hour standby period would be unwarranted. (NEEA, No. 21 at p. 4) AHRI and Rheem stated they do not support the addition of a minimum standby period length of 6 hours because it would extend the total test period time to over 24 hours. (AHRI, No. 17 at p. 6; Rheem, No. 14 at p. 4) A.O. Smith stated that adding 6 hours to the test would be significant and recommended that DOE investigate whether the addition is truly necessary, or if a less burdensome method could achieve the same goal. (A.O. Smith, No. 20 at p. 3) CSA referenced its test data, which included units with a standby period ranging from 5 minutes to over 7 hours, to demonstrate that standby time has very little effect on the overall UEF value. (CSA, No. 10 at p. 4)

The standby heat loss coefficient (

i.e.,

UA) is calculated from data recorded during the standby period. DOE reviewed its available test data and found that for the models reviewed, UA has very little effect on UEF, which is consistent with CSA's comment. UA is used only to adjust the daily water heating energy consumption to the nominal ambient temperature of 67.5 °F (19.7 °C). Given that the ambient temperature range is relatively narrow (

i.e.,

65 °F to 70 °F (18.3 °C to 21.1 °C)), the adjustment has only a minimal impact on the daily water heating energy consumption. Further, DOE found that the length of the recovery period has little effect on the resulting UA value. Therefore, DOE has tentatively determined that requiring a 6-hour standby period would not affect UA and UEF enough to justify the increased test burden associated with a

test that already could last longer than 24 hours.

Last Hour

In the April 2020 RFI, DOE requested feedback on whether it should consider an alternate procedure, like that in section 7.4.2.2 of the March 2019 ASHRAE Draft 118.2 (and section 7.4.3.2 of the April 2021 ASHRAE Draft 118.2), for the last hour of the 24-hour simulated-use test. 85 FR 21104, 21111 (April 16, 2020). DOE further requested feedback on whether the addition of standby loss in the total energy use calculation adequately represents the auxiliary energy use that is not measured between the minute prior to the start of the recovery occurring between hours 23 and 24, and hour 24 of the 24-hour simulated-use test.

Id.

CSA requested that DOE revisit the procedure for the last hour of the 24-hour simulated-use test. CSA raised a number of questions with how the test procedure in section 5.4.2,

Test Sequence for Water Heaters with Rated Storage Volumes Greater Than or Equal to 2 Gallons,

is implemented, specifically with regard to when power is to be turned off and on. (CSA, No. 10 at p. 4)

Although not stated explicitly in section 5.4.2 of appendix E, in the case that the standby period is between the first and second draw clusters, power to the main burner, heating element, or compressor is disabled during the last hour of the 24-hour simulated-use test. In the case that the standby period is after the last draw of the 24-hour simulated-use test, power to the main burner, heating element, or compressor is not disabled.

Section 5.4.2 of appendix E states that during the last hour of the 24-hour simulated-use test, power to the main burner, heating element, or compressor shall be disabled; at 24 hours, record the reading given by the gas meter, oil meter, and/or the electrical energy meter as appropriate; and determine the fossil fuel and/or electrical energy consumed during the entire 24-hour simulated-use test and designate the quantity as Q.

Section 5.4.2 of appendix E also provides that in the case that the standby period is after the last draw of the 24-hour simulated-use test, an8-hour standby period is required, and this period may extend past hour 24. The procedures for the standby period after the last draw of the 24-hour simulated-use test allow for a recovery to occur at the end of the 8-hour standby period, which indicates that the power to the main burner, heating element, or compressor is not disabled. DOE's procedure as described may result in some confusion. Further, the method of determining the total energy use during the 24-hour simulated-use test, Q, and total test time are not explicitly stated for when a standby period occurs after the last draw of the 24-hour simulated-use test. As discussed in the following paragraphs, DOE is proposing to amend the procedures for the last hour of the 24-hour simulated-use test to explain how to end the test for both standby period scenarios.

CSA and NEEA stated that DOE should adopt the March 2019 ASHRAE Draft 118.2 approach. (CSA, No. 10 at p. 4; NEEA, No. 21 at p. 6)

In the March 2019 ASHRAE Draft 118.2 and April 2021 ASHRAE Draft 118.2, power is not disabled when the standby period occurs after the last draw of the test. But, if a recovery occurs between an elapsed time of 23 hours following the start of the test (hour 23) and 24 hours following the start of the test (hour 24), the following alternate approach is applied to determine the energy consumed during the 24-hour simulated-use test: The time, total energy used, and mean tank temperature are recorded at 1 minute prior to the start of the recovery occurring between hour 23 and hour 24, along with the average ambient temperature from 1 minute prior to the start of the recovery occurring between hour 23 and hour 24 to hour 24 of the 24-hour simulated-use test. These values are used to determine the total energy used by the water heater during the 24-hour simulated-use test. This alternate calculation combines the total energy used 1 minute prior to the start of the recovery occurring between hours 23 and 24 and the standby loss experienced by the tank during the time between the minute prior to the recovery start and hour 24. This provision in section 7.4.2.2 of the March 2019 ASHRAE Draft 118.2 and section 7.4.3.2 of the April 2021 ASHRAE Draft 118.2 does not require the water heater to be de-energized during the standby period. Disabling power to the water heater is typically a manual operation that requires the presence of a technician. In cases where the technician does not disable power at the correct time, a retest of the 24-hour simulated-use test may be necessary. To the extent this draft provision would eliminate the need to ensure that a unit is switched off for the last hour of the 24-hour simulated-use test, it could reduce test burden.

In response to the April 2020 RFI, CSA further stated that not including the pilot energy does not adequately represent auxiliary energy usage for water heaters with continuously burning pilot lights. (CSA, No. 10 at p. 5) DOE notes that in the last hour of the 24-hour simulated-use test, the power to the main burner is disabled. In practice, cutting off the gas flow to the main burner disables the pilot light as well. However, disabling power to the main burner could also be accomplished by reducing the thermostat setting to the minimum setting available, which would result in the water heater under test not initiating a recovery during the last hour and gas continuing to be supplied to the pilot light. Reducing the thermostat setting would be a manual operation performed by a technician, not an automated action, which increases the chances of an invalid test. CSA also stated that water heaters without standing pilots will have minimal energy consumption in the last hour compared to the overall energy consumption, and that the total energy use calculation adequately represents the auxiliary energy use for these water heaters.

Id.

AHRI and A.O. Smith stated that they are in the process of evaluating the March 2019 ASHRAE Draft 118.2 test procedure for the last hour of the 24-hour simulated-use test and will provide additional information after their evaluation is completed. (AHRI, No. 17 at p. 6; A.O. Smith, No. 20 at p. 3) Rheem stated that given the limited time for evaluation and testing of an alternate procedure, the current procedure for the last hour of the 24-hour simulated-use test in appendix E should be maintained. (Rheem, No. 14 at p. 5)

At this time, DOE has not been provided with the additional information from AHRI or A.O. Smith regarding the procedure for the last hour of the 24-hour simulated-use test, and agrees with Rheem that further evaluation of the alternate procedure presented in the March 2019 ASHRAE Draft 118.2 and April 2021 ASHRAE Draft 118.2 should be conducted before a determination is made. As stated previously, the procedure for the last hour of the 24-hour simulated-use test may benefit from further, more explicit instruction, and

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