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Proposed Rule2021-13773

Energy Conservation Program: Test Procedure for Dehumidifying Direct Expansion-Dedicated Outdoor Air Systems

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Published

July 7, 2021

Issuing agencies

Energy Department

Abstract

The U.S. Department of Energy (DOE) is proposing to establish definitions for ``direct expansion-dedicated outdoor air systems'' (DX- DOAS or DX-DOASes) and ``dehumidifying direct expansion-dedicated outdoor air systems'' (DDX-DOAS or DDX-DOASes). DX-DOASes are a category of small, large, and very large commercial package air conditioning and heating equipment under the Energy Policy and Conservation Act (EPCA), as amended. In addition, DOE is proposing to establish a test procedure to measure the energy efficiency of DDX- DOASes, which aligns with the most recent version of the relevant industry consensus test standards for DDX-DOASes, with certain minor modifications. Lastly, DOE is proposing to add supporting definitions, energy efficiency metrics for dehumidification and heating modes, and provisions governing public representations as part of this rulemaking. DOE welcomes written comment from the public on any subject within the scope of this document (including topics not specifically raised in this proposal), as well as the submission of data and other relevant information.

Full Text

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[Federal Register Volume 86, Number 127 (Wednesday, July 7, 2021)]
[Proposed Rules]
[Pages 36018-36060]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2021-13773]

[[Page 36017]]

Vol. 86

Wednesday,

No. 127

July 7, 2021

Part III

Department of Energy

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10 CFR Parts 429 and 431

Energy Conservation Program: Test Procedure for Dehumidifying Direct
Expansion-Dedicated Outdoor Air Systems; Proposed Rule

Federal Register / Vol. 86 , No. 127 / Wednesday, July 7, 2021 /
Proposed Rules

[[Page 36018]]

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DEPARTMENT OF ENERGY

10 CFR Parts 429 and 431

[EERE-2017-BT-TP-0018]
RIN 1904-AD93

Energy Conservation Program: Test Procedure for Dehumidifying
Direct Expansion-Dedicated Outdoor Air Systems

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

ACTION: Notice of proposed rulemaking and request for comment.

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SUMMARY: The U.S. Department of Energy (DOE) is proposing to establish
definitions for ``direct expansion-dedicated outdoor air systems'' (DX-
DOAS or DX-DOASes) and ``dehumidifying direct expansion-dedicated
outdoor air systems'' (DDX-DOAS or DDX-DOASes). DX-DOASes are a
category of small, large, and very large commercial package air
conditioning and heating equipment under the Energy Policy and
Conservation Act (EPCA), as amended. In addition, DOE is proposing to
establish a test procedure to measure the energy efficiency of DDX-
DOASes, which aligns with the most recent version of the relevant
industry consensus test standards for DDX-DOASes, with certain minor
modifications. Lastly, DOE is proposing to add supporting definitions,
energy efficiency metrics for dehumidification and heating modes, and
provisions governing public representations as part of this rulemaking.
DOE welcomes written comment from the public on any subject within the
scope of this document (including topics not specifically raised in
this proposal), as well as the submission of data and other relevant
information.

DATES: Comments: DOE will accept written comments, data, and
information regarding this notice of proposed rulemaking (NOPR) on or
before September 7, 2021. See section V, ``Public Participation,'' for
details.
Meeting: DOE will hold a webinar on Monday, August 2, 2021 from
10:00 a.m. to 4:00 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 <a href="http://www.regulations.gov">www.regulations.gov</a>. Follow the
instructions for submitting comments.
Alternatively, interested persons may submit comments, identified
by docket number EERE-2017-BT-TP-0018, by any of the following methods:
1. Federal eRulemaking Portal: <a href="http://www.regulations.gov">www.regulations.gov</a>.
2. Email: to <a href="/cdn-cgi/l/email-protection#62210d0f0f23212a0703160b0c052713170b122103165052535536325252535a2207074c060d074c050d14">[email&#160;protected]</a>. Include
docket number EERE-2017-BT-TP-0018 in the subject line of the message.
No telefacsimiles (faxes) will be accepted. For detailed
instructions on submitting comments and additional information on this
process, see section V of this document (Public Participation).
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 accepting only
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/webinar attendee lists and transcripts, comments, and other
supporting documents/materials, is available for review at
<a href="http://www.regulations.gov">www.regulations.gov</a>. All documents in the docket are listed in the
<a href="http://www.regulations.gov">www.regulations.gov</a> 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: <a href="http://www.regulations.gov/#docketDetail">www.regulations.gov/#docketDetail</a>;D=EERE-2017-BT-TP-0018. The docket web page contains
instructions on how to access all documents, including public comments,
in the docket. See section V (Public Participation) for information on
how to submit comments through <a href="http://www.regulations.gov">www.regulations.gov</a>.

FOR FURTHER INFORMATION CONTACT: Ms. Catherine Rivest, 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) 586-7335. Email:
<a href="/cdn-cgi/l/email-protection#65241515090c040b06003611040b010417011634100016110c0a0b162500004b010a004b020a13">[email&#160;protected]</a>.
Mr. Eric Stas, U.S. Department of Energy, Office of the General
Counsel, GC-33, 1000 Independence Avenue SW, Washington, DC 20585.
Telephone: (202) 586-5827. Email: <a href="/cdn-cgi/l/email-protection#baffc8d3d994e9cedbc9fad2cb94ded5df94ddd5">[email&#160;protected]</a>v.
For further information on how to submit a comment, review other
public comments and the docket, or participate in the webinar, contact
the Appliance and Equipment Standards Program staff at (202) 287-1445
or by email: <a href="/cdn-cgi/l/email-protection#a0e1d0d0ccc9c1cec3c5f3d4c1cec4c1d2c4d3f1d5c5d3d4c9cfced3e0c5c58ec4cfc58ec7cfd6">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION: DOE proposes to incorporate by reference the
following industry standards into title 10 of the Code of Federal
Regulations (CFR) part 431:

Air-Conditioning, Heating, and Refrigeration Institute (AHRI) Standard
920-2020 (I-P), ``2020 Standard for Performance Rating of Direct
Expansion-Dedicated Outdoor Air System Units,'' approved February 4,
2020.
American National Standards Institute (ANSI)/AHRI Standard 1060-2018,
``2018 Standard for Performance Rating of Air-to-Air Exchangers for
Energy Recovery Ventilation Equipment,'' approved 2018.

Copies of AHRI Standard 920-2020 (I-P), and ANSI/AHRI Standard
1060-2018 can be obtained from the Air-conditioning, Heating, and
Refrigeration Institute, 2311 Wilson Blvd., Suite 400, Arlington, VA
22201, (703) 524-8800, or online at: <a href="http://www.ahrinet.org">www.ahrinet.org</a>.

ANSI/American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) Standard 37-2009, ``Methods of Testing for Rating
Electrically Driven Unitary Air-Conditioning and Heat Pump Equipment,''
ASHRAE approved June 24, 2009.
ANSI/ASHRAE Standard 41.1-2013, ``Standard Method for Temperature
Measurement,'' ANSI approved January 30, 2013.
ANSI/ASHRAE Standard 41.6-2014, ``Standard Method for Humidity
Measurement,'' ANSI approved July 3, 2014.
ANSI/ASHRAE Standard 198-2013, ``Method of Test for Rating DX-Dedicated
Outdoor Air Systems for Moisture Removal Capacity and Moisture Removal
Efficiency,'' ANSI approved January 30, 2013.

Copies of ANSI/ASHRAE Standard 37-2009, ANSI/ASHRAE Standard 41.1-
2013, ANSI/ASHRAE Standard 41.6-2014, and ANSI/ASHRAE Standard 198-2013
can be obtained from the American Society of Heating,

[[Page 36019]]

Refrigerating and Air-Conditioning Engineers, 180 Technology Parkway,
Peachtree Corners, GA 30092, (404) 636-8400, or online at:
<a href="http://www.ashrae.org">www.ashrae.org</a>.
See section IV.M of this document for a further discussion of these
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. Equipment Coverage
2. Scope of Test Procedure
3. Capacity Limit
4. Industry Terminology
B. Test Procedure for Dehumidifying Dedicated Outdoor Air
Systems
1. Industry Consensus Test Standards
2. Efficiency Metrics
a. Dehumidification Metric
b. Heating Metric
c. ISMRE2 and ISCOP2 Weighting Factors
3. Test Method
a. Definitions
b. Break-In Period
c. Airflow-Measuring Apparatus
d. Test Operating Conditions
i. Target Supply and Return Airflow Rates
ii. Units With Cycle Reheat Functions
iii. Target Supply Air Dry-Bulb Temperature
iv. Target Supply Air Dew-Point Temperature
v. Units With Staged Capacity Control
e. Water-Cooled and Water-Source Heat Pump DX-DOAS Equipment
i. Test Conditions for Multiple-Inlet Water Sources
ii. Condenser Liquid Flow Rate
iii. Water Pump Effect
iv. Energy Consumption of Heat Rejection Fans and Chillers
v. Chilled Water Coil Exclusion
f. Defrost Energy Use for Air-Source Heat Pump
g. General Control Setting Requirements
h. Ventilation Energy Recovery Systems
i. Exhaust Air Transfer and Leakage
ii. Purge Angle Setting
iii. Return Air External Static Pressure Requirements
iv. Target Return Airflow Rate
i. Demand-Controlled Ventilation
j. Tolerances for Supply and Return Airflow and External Static
Pressure
k. Secondary Dehumidification and Heating Capacity Tests
l. Corrections
i. Calculation of the Degradation Coefficient
ii. Non-Standard Low-Static Motor
iii. Calculation of Supplementary Heat Penalty
4. Determination of Represented Values
a. Basic Model
b. Sampling Plan Requirements
c. Multiple Refrigerants
d. Alternative Energy-Efficiency Determination Methods
e. Rounding
5. Configuration of Unit Under Test
C. Other Comments
D. Test Procedure Costs, Harmonization, and Other Topics
1. Test Procedure Costs and Impact
2. Harmonization With Industry Standards
3. Other Test Procedure Topics
E. Compliance Date
IV. Procedural Issues and Regulatory Review
A. Review Under Executive Order 12866
B. Review Under the Regulatory Flexibility Act
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. Procedure for Submitting Prepared General Statements for
Distribution
C. Conduct of the Webinar
D. Submission of Comments
E. Issues on Which DOE Seeks Comment
VI. Approval of the Office of the Secretary

I. Authority and Background

Small, large, and very large commercial package air conditioning
and heating equipment are included in the list of ``covered equipment''
for which DOE is authorized to establish and amend energy conservation
standards and test procedures. (42 U.S.C. 6311(1)(B)-(D)) As defined by
the Energy Policy and Conservation Act, as amended (EPCA), ``commercial
package air conditioning and heating equipment'' means air-cooled,
water-cooled, evaporatively-cooled, or water-source (not including
ground-water-source) electrically operated, unitary central air
conditioners and central air conditioning heat pumps for commercial
application. (42 U.S.C. 6311(8)(A)) Industry standards generally
describe unitary central air conditioning equipment as one or more
factory-made assemblies that normally include an evaporator or cooling
coil and a compressor and condenser combination. Units equipped to also
perform a heating function are included as well.\1\ Direct expansion-
dedicated outdoor air systems (DX-DOASes) provide conditioning of
outdoor ventilation air using a refrigeration cycle consisting of a
compressor, condenser, expansion valve, and evaporator,\2\ and
therefore, DOE has initially concluded that DX-DOASes are a category of
commercial package air conditioning and heating equipment subject to
EPCA. An industry consensus test standard has been established for a
subset of DX-DOASes (i.e., dehumidifying DX-DOASes (DDX-DOASes)), which
are the subject of this test procedure proposal. The following sections
discuss DOE's authority to establish test procedures for DDX-DOASes, as
well as relevant background information regarding DOE's proposed
adoption of the industry consensus test standard, and proposed
clarifications to the industry test procedure for this equipment.
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\1\ See American Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE) Standard 90.1, ``Energy Standard for
Buildings Except Low-Rise Residential Buildings.''
\2\ Other types of dedicated outdoor air systems are available
that do not utilize direct expansion (e.g., units that use chilled
water, rather than refrigerant, as the heat transfer medium); these
are discussed in section III.B.3.e.v. of this document.
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A. Authority

EPCA,\3\ as amended, among other things, authorizes DOE to regulate
the energy efficiency of a number of consumer products and certain
industrial equipment. Title III, Part C \4\ of EPCA, Public Law 94-163
(42 U.S.C. 6311-6317, as codified), added by Public Law 95-619, Title
IV, Sec. 441(a), established the Energy Conservation Program for
Certain Industrial Equipment, which sets forth a variety of provisions
designed to improve energy efficiency. This covered equipment includes
small, large, and very large commercial package air conditioning and
heating equipment. (42 U.S.C. 6311(1)(B)-(D)) DOE has initially
determined that commercial package air conditioning and heating
equipment includes DX-DOASes. As discussed in section I.B of this
document, DX-DOASes had not previously been addressed in DOE
rulemakings and are not currently subject to Federal test procedures or
energy conservation standards.
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\3\ All references to EPCA in this document refer to the statute
as amended through the Energy Act of 2020, Public Law 116-260 (Dec.
27, 2020).
\4\ For editorial reasons, upon codification in the U.S. Code,
Part C was redesignated Part A-1.
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Under EPCA, DOE's energy conservation program consists essentially
of four parts: (1) Testing, (2) labeling, (3) Federal energy
conservation standards, and (4) certification and enforcement
procedures. Relevant provisions of EPCA specifically include
definitions (42 U.S.C. 6311), energy conservation standards (42 U.S.C.
6313), test procedures (42 U.S.C. 6314),

[[Page 36020]]

labeling provisions (42 U.S.C. 6315), and the authority to require
information and reports from manufacturers (42 U.S.C. 6316).
The Federal testing requirements consist of test procedures that
manufacturers of covered equipment must use as the basis for: (1)
Certifying to DOE that their equipment complies with the applicable
energy conservation standards adopted pursuant to EPCA (42 U.S.C.
6316(b); 42 U.S.C. 6296), and (2) making representations about the
efficiency of that equipment (42 U.S.C. 6314(d)). Similarly, DOE uses
these test procedures to determine whether the equipment complies with
relevant standards promulgated under EPCA.
Federal energy efficiency requirements for covered equipment
established under EPCA generally supersede State laws and regulations
concerning energy conservation testing, labeling, and standards. (42
U.S.C. 6316(a) and (b); 42 U.S.C. 6297) DOE may, however, 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. 6316(b)(2)(D))
Under 42 U.S.C. 6314, the statute also sets forth the criteria and
procedures DOE is required to follow when prescribing or amending test
procedures for covered equipment. Specifically, EPCA requires that any
test procedure prescribed or amended shall be reasonably designed to
produce test results which measure energy efficiency, energy use, or
estimated annual operating cost of covered equipment during a
representative average use cycle and requires that test procedures not
be unduly burdensome to conduct. (42 U.S.C. 6314(a)(2))
EPCA requires that the test procedures for commercial package air
conditioning and heating equipment be those generally accepted industry
testing procedures or rating procedures developed or recognized by the
Air-Conditioning, Heating, and Refrigeration Institute (AHRI) or by the
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE), as referenced in ASHRAE Standard 90.1, ``Energy
Standard for Buildings Except Low-Rise Residential Buildings'' (ASHRAE
Standard 90.1). (42 U.S.C. 6314(a)(4)(A)) Further, if such an industry
test procedure is amended, DOE must update its test procedure to be
consistent with the amended industry test procedure, unless DOE
determines, by rule published in the Federal Register and supported by
clear and convincing evidence, that such amended test procedure would
not meet the requirements in 42 U.S.C. 6314(a)(2) and (3), related to
representative use and test burden. (42 U.S.C. 6314(a)(4)(B))
EPCA also requires that, at least once every seven years, DOE
evaluate test procedures for each type of covered equipment, including
commercial package air conditioning and heating equipment to determine
whether amended test procedures would more accurately or fully comply
with the requirements for the test procedures not to 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. (42 U.S.C.
6314(a)(1)-(3)) In addition, if DOE determines that a test procedure
amendment is warranted, it 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)) 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. 6314(a)(1)(A)(ii))
As discussed in section I.B of this document, a test procedure for
a subset of DX-DOASes (i.e., DDX-DOASes), was first specified by ASHRAE
Standard 90.1 in the 2016 edition (ASHRAE Standard 90.1-2016). Pursuant
to 42 U.S.C. 6314(a)(4)(B), and following updates to the relevant test
procedures which were referenced in ASHRAE Standard 90.1, DOE is
publishing this NOPR proposing to establish a test procedure for DDX-
DOASes in satisfaction of its aforementioned obligations under EPCA.

B. Background

From a functional perspective, DX-DOASes operate similarly to other
categories of commercial package air conditioning and heat pump
equipment, in that they provide conditioning using a refrigeration
cycle consisting of a compressor, condenser, expansion valve, and
evaporator. DX-DOASes provide ventilation and conditioning of 100-
percent outdoor air to the conditioned space, whereas for typical
commercial package air conditioners that are central air conditioners,
outdoor air makes up only a small portion of the total airflow (usually
less than 50 percent). DX-DOASes are typically installed in addition to
a local, primary cooling or heating system (e.g., commercial unitary
air conditioner, variable refrigerant flow system, chilled water
system, water-source heat pumps)--the DX-DOAS conditions the outdoor
ventilation air, while the primary system provides cooling or heating
to balance building shell and interior loads and solar heat gain.
According to ASHRAE, a well-designed system using a DX-DOAS can
ventilate a building at lower installed cost, reduce overall annual
building energy use, and improve indoor environmental quality.\5\
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\5\ From the June 2018 ASHRAE eSociety Newsletter (Available at:
<a href="http://www.ashrae.org/news/esociety/what-s-new-in-doas-and-refrigerant-research">www.ashrae.org/news/esociety/what-s-new-in-doas-and-refrigerant-research</a>) (Last accessed May 24, 2021).
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On October 26, 2016, ASHRAE published ASHRAE Standard 90.1-2016,
which for the first time specified a test standard and efficiency
standards for DX-DOASes. ASHRAE Standard 90.1-2016 (and the subsequent
2019 edition) defines DX-DOAS as a type of air-cooled, water-cooled, or
water-source factory assembled product that dehumidifies 100% outdoor
air to a low dew point and includes reheat that is capable of
controlling the supply dry-bulb temperature of the dehumidified air to
the designed supply air temperature. This conditioned outdoor air is
then delivered directly or indirectly to the conditioned spaces. It may
precondition outdoor air by containing an enthalpy wheel, sensible
wheel, desiccant wheel, plate heat exchanger, heat pipes, or other heat
or mass transfer apparatus.
Although ASHRAE Standard 90.1-2016 uses the term ``DX-DOAS,'' the
definition of this term provided therein describes a subset of DX-
DOASes, specifically DDX-DOASes. The ASHRAE definition of ``DX-DOAS''
is generally equivalent to the equipment DOE is proposing to define as
DDX-DOAS and for which DOE is proposing to adopt the industry consensus
standard. DDX-DOASes dehumidify air to a low dew point. When operating
in humid conditions, the dehumidification load from the outdoor
ventilation air is a much larger percentage of the total cooling load
for a DDX-DOAS than for a typical commercial air conditioner.
Additionally, compared to a typical commercial air conditioner, the
amount of total cooling (both sensible and latent) is much greater per
pound of air for a DDX-DOAS at design conditions (i.e., the warmest/
most humid expected summer conditions), and a DDX-DOAS is designed to
accommodate greater variation in entering air temperature and humidity
(i.e., a typical commercial air conditioner would not be able to
dehumidify 100-percent outdoor ventilation air to the levels achieved
by

[[Page 36021]]

a DDX-DOAS). Not all DX-DOASes have this dehumidification capability,
which is why DOE is proposing a separate definition. (See section
III.B.2.a of this NOPR for further details.)
The amendment to ASHRAE Standard 90.1 to specify an industry test
standard for equipment that DOE calls DDX-DOAS triggered DOE's
obligations vis-[agrave]-vis test procedures under 42 U.S.C.
6314(a)(4)(B), as outlined previously. On July 25, 2017, DOE published
a request for information (RFI) (the July 2017 ASHRAE TP RFI) in the
Federal Register to collect information and data to consider new and
amended DOE test procedures for commercial package air conditioning and
heating equipment, given the test procedure updates included in ASHRAE
Standard 90.1-2016. 82 FR 34427. As part of the July 2017 ASHRAE TP
RFI, DOE requested comment on several aspects regarding test procedures
for DDX-DOASes in consideration of adopting a new DOE test procedure
for this equipment, including: Incorporation by reference of the
relevant industry test standard(s); efficiency metrics and
calculations, and additional topics that may inform DOE's decisions in
a future test procedure rulemaking.\6\ 82 FR 34427, 34435-34439 (July
25, 2017). On October 25, 2019, ASHRAE published an updated version of
ASHRAE Standard 90.1 (i.e., ASHRAE Standards 90.1-2019), which
maintained the DDX-DOAS provisions as first introduced in ASHRAE
Standard 90.1-2016 without revisions.
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\6\ In the July 2017 ASHRAE TP RFI, DOE referred to DDX-DOASes
simply as ``DOASes.''
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DOE received a number of comments from interested parties in
response to the July 2017 ASHRAE TP RFI, which covered multiple
categories of equipment. Table I-1 lists the commenters relevant to
DDX-DOASes, along with each commenter's abbreviated name used
throughout this NOPR. DOE considered these comments in the preparation
of this NOPR. Discussion of the relevant comments, and DOE's responses,
are provided in the appropriate sections of this document.

Table I-1--Interested Parties Providing DX-DOAS-Related Comments on the
July 2017 ASHRAE Test Procedure RFI
------------------------------------------------------------------------
Name Abbreviation Type \1\
------------------------------------------------------------------------
Air-Conditioning, Heating, and AHRI................. IR
Refrigeration Institute.
Appliance Standards Awareness Project Joint Advocates...... EA
(ASAP), Alliance to Save Energy
(ASE), American Council for an
Energy-Efficient Economy (ACEEE),
Northwest Energy Efficiency Alliance
(NEEA), and Northwest Power and
Conservation Council (NPCC).
Carrier Corporation, part of United Carrier.............. M
Technologies Climate, Controls &
Security (CCS) business.
Goodman Global, Inc.................. Goodman.............. M
The Greenheck Group.................. Greenheck............ M
Ingersoll Rand....................... Ingersoll Rand....... M
Lennox International, Inc............ Lennox............... M
Mitsubishi Electric Cooling & Heating Mitsubishi........... M
\2\.
National Comfort Institute........... NCI.................. IR
Pacific Gas and Electric Company CA IOUs.............. U
(PG&E), Southern California Gas
Company (SoCalGas), San Diego Gas
and Electric (SDG&E), and Southern
California Edison (SCE),
collectively referred to as
California Investor-Owned Utilities
(CA IOUs).
------------------------------------------------------------------------
\1\ EA: Efficiency/Environmental Advocate; IR: Industry Representative;
M: Manufacturer; U: Utility.
\2\ Mitsubishi commented that it fully supports all of the comments
submitted by AHRI on DX-DOAS issues.

On February 14, 2020, DOE published a final rule updating its
procedures for consideration of new and amended energy conservation
standards at 10 CFR part 430, subpart C, appendix A, ``Procedures,
Interpretations, and Policies for Consideration of New or Revised
Energy Conservation Standards and Test Procedures for Consumer Products
and Certain Commercial/Industrial Equipment'' (the Process Rule). 85 FR
8626. As part of the update, the Process Rule now applies explicitly to
commercial and industrial equipment. 10 CFR 431.4. The updated Process
Rule also includes provisions specific to the consideration of new and
amended energy conservation standards and test procedures for covered
equipment subject to the ASHRAE provisions of EPCA. See Process Rule,
10 CFR part 430, subpart C, appendix A, sections 2 and 9.
With respect to DOE's consideration of changes to the relevant
industry consensus test procedure(s) for covered ASHRAE equipment, the
Process Rule now provides that DOE will do so only if it can meet a
very high bar to demonstrate the ``clear and convincing evidence''
threshold. 10 CFR part 430, subpart C, appendix A, section 9(b). Clear
and convincing evidence would exist only where the specific facts and
data made available to DOE regarding a particular ASHRAE amendment
demonstrates that there is no substantial doubt that that the industry
test procedure does not meet the EPCA requirements. Id. DOE will make
this determination only after seeking data and information from
interested parties and the public to help inform DOE's views. DOE will
seek from interested stakeholders and the public data and information
to assist in making this determination, prior to publishing a proposed
rule to adopt a different test procedure. Id.

II. Synopsis of the Notice of Proposed Rulemaking

In this NOPR, DOE is proposing to establish a definition for DX-
DOAS as a category of commercial package air conditioning and heating
equipment and adopt a new test procedure for a subset of DX-DOASes
(i.e., DDX-DOASes), consistent with the industry consensus test
standard as specified in ASHRAE Standard 90.1-2019. The proposed test
procedure applies to all DDX-DOASes for which ASHRAE 90.1-2019
specifies standards, with the exception of ground-water-source DDX-
DOASes, as discussed in section III.A.1 of this NOPR. More
specifically, DOE proposes to update 10 CFR 431.96, ``Uniform test
method for the measurement of energy efficiency of commercial air
conditioners and heat pumps,'' to adopt a new test procedure for DDX-
DOASes as follows: (1) Incorporate by reference AHRI Standard 920-2020
(I-P), ``Performance Rating of

[[Page 36022]]

Direct Expansion-Dedicated Outdoor Air System Units'' (AHRI 920-2020),
the most recent version of the test procedure recognized by ASHRAE
Standard 90.1 for DDX-DOASes, and the relevant industry standards
referenced therein; (2) establish the scope of coverage for the DDX-
DOAS test procedure; (3) add definitions for DX-DOASes and DDX-DOASes,
as well as additional terminology required by the test procedure; (4)
adopt the integrated seasonal moisture removal efficiency, as measured
according to the most recent applicable industry standard (ISMRE2), and
integrated seasonal coefficient of performance (ISCOP2), as measured
according to the most recent applicable industry standard, as energy
efficiency descriptors for dehumidification and heating mode,
respectively; and (5) establish representation requirements. DOE
proposes to add a new Appendix B to Subpart F of Part 431, titled
``Uniform test method for measuring the energy consumption of
dehumidifying direct expansion-dedicated outdoor air systems,''
(Appendix B) that would include the new test procedure requirements for
DDX-DOASes. In conjunction, DOE proposes to amend Table 1 in 10 CFR
431.96 to identify the newly added Appendix B as the applicable test
procedure for testing DDX-DOASes. DOE has tentatively determined that
the proposed test procedure would not be unduly burdensome to conduct.
DOE's proposed actions are summarized in Table II.1 and addressed
in detail in section III of this document.

Table II.1--Summary of Proposed Test Procedure for DDX-DOASes
------------------------------------------------------------------------
Proposed test procedure Attribution
------------------------------------------------------------------------
Incorporates by reference AHRI 920-2020 and Adopt industry test
other relevant industry test standards procedure.
referenced by that standard. AHRI 920-2020
includes:
--test methods for DDX-DOAS with and
without ventilation energy recovery
systems (VERS);
--test operating conditions, including
Standard Rating Conditions, simulated
ventilation air conditions for
optional test methods for DDX-DOASes
with VERS, supply air target
conditions, supply and return airflow
rates, and external static pressure;
--testing instrumentation and apparatus
instructions;
--test operating and condition
tolerances \7\;
--a list of components that must be
present for testing; and
--provisions for testing units with
certain optional features.
Defines DX-DOASes as covered equipment Establish equipment
which meet the EPCA definition for small, coverage.
large, or very-large commercial package
air conditioning and heating equipment.
Defines the scope of coverage of the test Clarify scope of test
procedure, including defining DDX-DOASes procedure.
to distinguish them from other kinds of
equipment and a capacity limit based on
moisture removal capacity (MRC).
Adopts ISMRE2 and ISCOP2 as the seasonal Adopt industry test
efficiency descriptors for procedure.
dehumidification and heating mode,
respectively, as specified in AHRI 920-
2020.
Provides minor corrections and additional Clarify instructions in the
instruction consistent with AHRI 920-2020 industry test procedure.
by:
--specifying the external head pressure
requirements for DDX-DOASes with integral
water pumps;
--specifying general control setting
requirements;
--correcting a typographical error in
the calculation of the degradation
coefficient; and
--providing a missing definition
necessary for the interpretation of
the airflow setting instructions.
Specifies representation requirements, Provide for representations
including a basic model definition, of energy efficiency
sampling plan requirements, and use of consistent with other
alternative energy-efficiency commercial air conditioner/
determination methods (AEDMs). heat pump equipment.
------------------------------------------------------------------------

III. Discussion
---------------------------------------------------------------------------

\7\ ``Test operating tolerance'' refers to the maximum
permissible range that a measurement may vary over a specified test
interval. ``Test condition tolerance'' refers to the maximum
permissible difference between the average value of the measured
test parameter and the specified test condition.
---------------------------------------------------------------------------

The following sections discuss DOE's proposal to define DX-DOASes
as a category of small, large and extra-large commercial package air
conditioning and heating equipment and to adopt a new test procedure
for DDX-DOASes, a subset of DX-DOASes, and address relevant comments
received in response to specific issues DOE raised in the July 2017
ASHRAE TP RFI. Commenters' references to ``DX-DOASes'' or ``DOASes''
have been changed to ``DDX-DOASes'' where DOE understands the
commenters to be specifically discussing DX-DOASes that would meet the
dehumidification performance criterion as proposed.

A. Scope of Applicability

1. Equipment Coverage
As discussed, DOE has initially determined that DX-DOASes are a
category of small, large, and very large commercial package air
conditioning and heating equipment and, therefore, are covered
equipment under EPCA. (42 U.S.C. 6311(1)(B)-(D)) DX-DOASes operate
similarly to more typical commercial package air conditioning equipment
in that they provide conditioning of outdoor ventilation air using a
refrigeration cycle consisting of a compressor, condenser, expansion
valve, and evaporator. However, DX-DOASes are designed to provide
ventilation and conditioning of 100-percent outdoor air, while outdoor
air makes up only a small portion of the total airflow for typical
commercial package air conditioning and heating equipment (e.g.,
usually less than 50 percent).
As discussed further in section III.A.4 of this document, industry
provides several definitions for DX-DOASes, but DOE notes that the
industry definitions for ``DX-DOAS'' specifically refer to the DDX-
DOASes that are covered by the scope of those industry test standards,
which does not include non-dehumidifying (i.e., sensible-only) DX-
DOASes that exist on the market.
In this NOPR, DOE is proposing to define ``direct expansion-
dedicated outdoor air system, or DX-DOAS,'' as a category of small,
large, or very large commercial package air conditioning and heating
equipment which is capable of providing ventilation and conditioning of
100-percent outdoor air or marketed in materials (including but not
limited to, specification sheets, insert sheets, and online materials)
as having such capability. This proposed definition is based, in part,
on the definition in section 3.6 of AHRI 920-

[[Page 36023]]

2020, as discussed in section III.A.4 of this document.
The proposed definition of DX-DOAS would include all air-cooled,
air-source heat pump, and water-cooled equipment subcategories
specified in ASHRAE Standard 90.1. For water-source heat pump
equipment, ASHRAE Standard 90.1 includes three configurations--ground-
source, closed loop; ground-water-source; and water-source. The EPCA
definition for ``commercial package air conditioning and heating
equipment'' specifically excludes ground-water-source equipment (42
U.S.C. 6311(8)(A)), so in proposing to define (at 10 CFR 431.92) DX-
DOAS as a category of small, large, or very large commercial package
air conditioning and heating equipment, ground-water-source DX-DOASes
would be excluded from coverage under EPCA.
Issue-1: DOE requests comment on the proposed definition for
``direct expansion-dedicated outdoor air system.'' DOE also requests
comment on any additional characteristics not yet considered that could
help to distinguish DX-DOASes from other commercial package air
conditioning and heating equipment.
2. Scope of Test Procedure
DOE is proposing to establish a test procedure for a subset of DX-
DOASes (i.e., DDX-DOASes). When operating in humid conditions, the
dehumidification load is a much larger percentage of the total cooling
load for a DDX-DOAS than for a typical commercial package air
conditioning system. DDX-DOASes in particular handle a significantly
higher amount of total cooling (both sensible and latent) per pound of
air at design conditions (i.e., the warmest or most humid expected
summer conditions), and a DDX-DOAS is designed to accommodate greater
variation in entering air temperature and humidity, because outdoor
conditions can vary much more than typical indoor conditions. As
discussed, not all DX-DOASes are designed to dehumidify outdoor air at
the most humid expected summer conditions to a level consistent with
comfortable indoor conditions, such as a dew point temperature less
than 55 [deg]F (e.g., sensible-only cooling \8\ DX-DOASes). AHRI stated
that sensible-only 100-percent outdoor air units should not be covered
by ANSI/AHRI 920-2015 because they are not intended to dehumidify the
ventilation air. (AHRI, No. 11 at pp. 10-11) \9\
---------------------------------------------------------------------------

\8\ ``Sensible cooling'' refers to the process of cooling air by
reducing its dry bulb temperature without changing its moisture
content.
\9\ A notation in the form ``AHRI, No. 11 at pp. 10-11''
identifies a written comment: (1) Made by AHRI; (2) recorded in
document number 11 that is filed in the docket of this test
procedure rulemaking (Docket No. EERE-2017-BT-TP-0018) and available
for review at <a href="http://www.regulations.gov">www.regulations.gov</a>; and (3) which appears on pages 10
through 11 of document number 11.
---------------------------------------------------------------------------

Because DOE is aware of sensible-only DX-DOASes, DOE aims to
further delineate those DX-DOASes that would be subject to the proposed
test procedure (i.e., DDX-DOASes). Section 2.2 of AHRI 920-2020
explicitly excludes ``Sensible-only 100% Outdoor Air Units'' from the
scope of its test standard. Accordingly, DOE proposes to define DDX-
DOASes (the subject of this proposed test procedure) in 10 CFR 431.92
as those DX-DOASes specifically having the capability to dehumidify air
to a dew point of 55 [deg]F when operating under Standard Rating
Condition A as specified in Table 4 or Table 5 of AHRI 920-2020 with a
barometric pressure of 29.92 in Hg. The 55 [deg]F dew point is
specified in ANSI/AHRI 920-2015 and AHRI 920-2020 as the maximum dew
point temperature for the supply air for the dehumidification mode
tests.\10\ This maximum dew point temperature requirement for DDX-
DOASes provides a key differentiator from other DX-DOASes, which
typically cannot dehumidify 100-percent outdoor air to a dew point this
low. This element is consistent with the definition in AHRI 920-2020.
---------------------------------------------------------------------------

\10\ AHRI 920-2020 acknowledges the influence of barometric
pressure on humidity ratio for the inlet air conditions specified in
terms of dry bulb and wet bulb temperature, allowing an upward
adjustment of the maximum supply air dew point temperature that must
be achieved, such that the moisture removal rate matches that which
would occur at standard barometric pressure when supplying 55 [deg]F
dew-point supply air--this maximum supply air dew point increases
linearly as barometric pressure decreases, up to 57.3 [deg]F at the
minimum-allowed 13.7 psia test pressure.
---------------------------------------------------------------------------

AHRI 920-2020 does not specify at what airflow the dehumidification
element is to be evaluated. DOE proposes to include within the proposed
definition of DDX-DOAS that the DDX-DOAS be capable of providing the
specified dehumidification capability for any portion of the range of
air flow rates advertised in manufacturer materials. This provision
would provide additional specificity to the definition found in AHRI
920-2020 to account for manufacturers that may specify a range of
airflows for a given model.
As proposed, the test procedure would apply to DDX-DOASes within
the capacity limits as discussed in the following section.
Issue-1: DOE requests comment on the proposed definition for
``dehumidifying direct expansion-dedicated outdoor air system.''
Specifically, DOE requests comment on the proposed criteria for
distinguishing a ``dehumidifying direct expansion-dedicated outdoor air
system'' from a ``direct expansion-dedicated outdoor air system'' more
generally. DOE also requests comment on any additional characteristics
not yet considered that could help to distinguish DDX-DOASes from DX-
DOASes more generally.
3. Capacity Limit
As stated, EPCA defines as covered equipment small, large, and very
large commercial package air conditioning and heating equipment. (42
U.S.C. 6311(1)(B)-(D)) EPCA defines ``small commercial package air
conditioning and heating equipment'' as commercial package air
conditioning and heating equipment that is rated below 135,000 Btu per
hour (cooling capacity). (42 U.S.C. 6311(8)(B)) The term ``large
commercial package air conditioning and heating equipment'' means
commercial package air conditioning and heating equipment that is
rated--(i) at or above 135,000 Btu per hour; and (ii) below 240,000 Btu
per hour (cooling capacity). (42 U.S.C. 6311(8)(C)) The term ``very
large commercial package air conditioning and heating equipment'' means
commercial package air conditioning and heating equipment that is
rated--(i) at or above 240,000 Btu per hour; and (ii) below 760,000 Btu
per hour (cooling capacity). (42 U.S.C. 6311(8)(D))
In response to the July 2017 ASHRAE TP RFI, AHRI commented that
DOE's regulations for DDX-DOASes should be capped at a reasonable
capacity, similar to the 760,000 Btu/h limit for commercial packaged
air conditioning equipment. AHRI stated that laboratory limitations may
limit testing using ANSI/AHRI 920-2015 to 300 lbs. of moisture per hour
at Standard Rating Condition A and to units not physically larger than
more typical commercial package air conditioning and heating equipment
with a capacity of 760,000 Btu/h. The commenter also stated that the
market for these larger, typical commercial package air conditioning
equipment and DDX-DOAS units (with a capacity greater than 760,000 Btu/
h, or equivalent) is very small and customized. AHRI stated that the
customization helps customers minimize energy consumption for their
application. (AHRI, No. 11 at p. 20)
As discussed, DOE has tentatively concluded that DX-DOASes meet the
EPCA definition for ``commercial package air conditioning and heating
equipment,'' and, thus, are to be considered as a category of that
covered equipment. (42 U.S.C. 6311(8)(A)) The upper capacity limit of
commercial

[[Page 36024]]

package air conditioning subject to the DOE test procedures is 760,000
Btu per hour, based on the definition of ``very large commercial
package air conditioning and heating equipment.'' (42 U.S.C.
6311(8)(D))
For DDX-DOASes specifically, AHRI 920-2020 does not provide a
method for determining capacity in terms of Btu per hour, but instead,
it specifies a determination of capacity in terms of moisture removal
capacity (MRC). DOE proposes to translate the upper capacity for
coverage of commercial package air conditioning and heating units
established in EPCA (i.e., 760,000 Btu per hour) from Btu per hour to
MRC for DDX-DOASes. Specifically, DOE is proposing, consistent with
section 6 of AHRI 920-2020, to translate the upper limit from Btu per
hour to MRC of the DDX-DOAS when delivering dehumidified supply air at
a 55 [deg]F dew point. Manufacturers would use their tested value of
MRC to determine if a DDX-DOAS is subject to the test procedure.
To translate Btu per hour to MRC, DOE calculated the maximum
airflow that could be supplied at a 55 [deg]F dewpoint for Standard
Rating Condition A as specified in Table 4 and Table 5 of AHRI 920-2020
by cooling and dehumidifying it with an evaporator with a refrigeration
capacity of 760,000 Btu per hour. DOE calculated this based on air
entering the evaporator at Standard Rating Condition A (95 [deg]F dry-
bulb temperature and 78 [deg]F wet-bulb temperature) and air exiting
the evaporator at 55 [deg]F dew point and 95-percent relative humidity
at a standard barometric pressure of 29.92 in Hg. DOE then calculated
the MRC that corresponds to those conditions. Based on these
calculations, DOE is proposing to limit the scope of this proposed test
procedure to DDX-DOAS units with a MRC less than 324 lbs. per hour
based on Standard Rating Condition A as specified in Table 4 or Table 5
of AHRI 920-2020.
Issue-2: DOE seeks comment on its translation of Btu per hour to
MRC and specifically its proposal to translate the upper capacity limit
for DDX-DOASes such that a model would be considered in scope if it has
an MRC less than 324 lbs. per hour.
4. Industry Terminology
As stated, DOE is proposing definitions for DX-DOAS and DDX-DOAS
following a review of industry standards and consistent with the
applicability of the relevant industry testing standard. Both ANSI/AHRI
920-2015 and ANSI/ASHRAE 198-2013 include definitions for ``DX-
Dedicated Outdoor Air System Units.'' Section 3.3 of ANSI/AHRI 920-2015
defines ``DX-Dedicated Outdoor Air System Units'' as a type of air-
cooled, water-cooled, or water-source factory assembled product which
dehumidifies 100-percent outdoor air to a low dew point, and includes
reheat that is capable of controlling the supply dry-bulb temperature
of the dehumidified air to the designed supply air \11\ temperature.
This conditioned outdoor air is then delivered directly or indirectly
to the conditioned space(s). It may pre-condition outdoor air by
containing an enthalpy wheel, sensible wheel, desiccant wheel, plate
heat exchanger, heat pipes, or other heat or mass transfer apparatus.
This is the same definition used in ASHRAE Standard 90.1-2019.
---------------------------------------------------------------------------

\11\ ``Supply air'' for a DDX-DOAS refers to conditioned air
that is supplied to the conditioned space.
---------------------------------------------------------------------------

Section 3 of ANSI/ASHRAE 198-2013 defines a ``DX Dedicated Outdoor
Air Systems Unit (DX-DOAS)'' as a type of air-cooled, water-cooled, or
water-source factory-assembled product that is capable of dehumidifying
100-percent outdoor air to a low dew point and may be capable of
controlling the dry-bulb temperature of the dehumidified air to the
designed supply air temperature. This conditioned outdoor air may be
delivered directly or indirectly to the conditioned space(s). It may
pre-condition outdoor air prior to direct expansion cooling by
incorporating an enthalpy wheel, sensible wheel, desiccant wheel, plate
heat exchanger, heat pipes, or other heat or mass transfer apparatus.
The product may also include a supplementary heating system for use
when outdoor air requires heating beyond the capability of the
refrigeration system and/or other heat transfer apparatus.
As part of the July 2017 ASHRAE TP RFI, DOE requested comment on
certain aspects of these two industry definitions of dedicated outdoor
air systems. 82 FR 34427, 34435-34436 (July 25, 2017). On February 4,
2020, AHRI published AHRI 920-2020, which made changes to the
definition of ``Dedicated Outdoor Air System Unit'' as compared to the
definition in ANSI/AHRI 920-2015 (and ASHRAE Standard 90.1-2019).
Section 3.6 of AHRI 920-2020 defines ``Dedicated Outdoor Air System
Unit'' as a type of air-cooled, evaporatively-cooled, or water-cooled
air-conditioner, or an air-source or water source heat pump, that is a
factory assembled product designed and marketed and sold to provide
ventilation and dehumidification of 100% outdoor air, is capable of
dehumidifying air to a 55 [deg]F dew point when operating under
Standard Rating Condition A as specified in Table 4 or Table 5 of this
test standard with a barometric pressure of 29.92 in Hg, and may
include reheat. It may include pre-conditioning of outdoor air using an
enthalpy wheel, sensible wheel, desiccant wheel, plate heat exchanger,
heat pipes, or other heat or mass transfer apparatus. Heating
components are optional and may include electrical resistance, steam,
hot water, or gas heat. In addition, it may provide for air cleaning or
may include mixing box or economizer dampers to allow return air to be
intermittently used as allowed by the controls.
Both ANSI/AHRI 920-2015 and ANSI/ASHRAE 198-2013 address equipment
that dehumidifies (or is capable of dehumidifying) 100-percent outdoor
air to a low dew point. As discussed, in its review of available
equipment, DOE found units marketed as ``dedicated outdoor air
systems,'' and other units marketed for ``100-percent outdoor air''
applications, both of which can also operate with less than 100-percent
outdoor air. Such units have a return air damper that allows modulating
the amount of return air that is recirculated from the conditioned
space and mixed with the incoming outdoor air before the mixed air is
conditioned. More typical commercial package air conditioning equipment
also often incorporates a similar damper to mix return air and outdoor
air. Additionally, like the industry definitions for dedicated outdoor
air systems, which DOE notes would be DDX-DOASes as that term is
proposed to be defined, some categories of commercial package air
conditioning equipment can dehumidify 100-percent outdoor air, although
typically not to a dew point as low as the industry specification for
DDX-DOASes.
As part of the July 2017 ASHRAE TP RFI, DOE requested information
on the range of the maximum percentage of return air intake relative to
total airflow of models of equipment that DOE generally referred to as
``DOASes'' in order to determine whether the maximum return air
percentage is an important distinguishing feature of DDX-DOASes. DOE
also requested information on the difference in dehumidification
capabilities of more typical commercial package air conditioning
equipment and equipment that DOE referred to as DOASes when operating
with 100-percent outdoor air. 82 FR 34427, 34435 (July 25, 2017).
Ingersoll Rand and Carrier commented that there are not one or two
features or criteria that definitively distinguish DDX-DOASes from more

[[Page 36025]]

typical commercial package air conditioning equipment. (Ingersoll Rand,
No. 12 at p. 2; Carrier, No. 6 at p. 2) AHRI and Carrier commented that
there may be several potential applications for DDX-DOASes, some of
which may not be 100-percent outdoor air. (AHRI, No. 11 at p. 9;
Carrier, No. 6 at p. 2) AHRI and Ingersoll Rand stated, for example,
that DDX-DOASes may be supplied with recirculation dampers that allow
them to efficiently dehumidify recirculated air when the building is
unoccupied. AHRI stated that, as a result, it is not possible to select
a specific crossover percentage of return air intake relative to total
airflow that would differentiate DDX-DOASes from more typical
commercial package air conditioning equipment. (AHRI, No. 11 at p. 9;
Ingersoll Rand, No. 12 at p. 2) Goodman supported AHRI's position,
adding that when the return air intake relative to the total airflow is
less than 10-30 percent, ANSI/AHRI 920-2015 is more appropriate than
ANSI/AHRI 340/360 \12\ in non-western climates. (Goodman, No. 14 at p.
2)
---------------------------------------------------------------------------

\12\ ANSI/AHRI Standard 340/360, ``Performance Rating of
Commercial and Industrial Unitary Air-conditioning and Heat Pump
Equipment'' (Available at: <a href="http://www.ahrinet.org/">www.ahrinet.org/</a>) (Last accessed April
19, 2021).
---------------------------------------------------------------------------

As discussed, not all DX-DOASes are designed to provide
dehumidification (to a low dew point) over larger variation in entering
air temperature and humidity. As such, DOE is proposing to define DDX-
DOAS to distinguish such equipment from DX-DOAS more generally, as
provided in the previous sections. The DDX-DOAS definition is
consistent with the definition in section 3.6 of AHRI 920-2020 for the
equipment subject to the scope of that industry test standard.
DOE noted in the July 2017 ASHRAE TP RFI that one difference
between the definitions in ANSI/ASHRAE 198-2013 and ANSI/AHRI 920-2015
(and now AHRI 920-2020) is related to reheat. ANSI/AHRI 920-2015
specifies that a Direct Expansion-Dedicated Outdoor Air System Unit
includes reheat, which is used to raise the temperature of cooled and
dehumidified air to a design supply air temperature. The ANSI/ASHRAE
198-2013 definition provides that a DX Dedicated Outdoor Air Systems
Unit, as defined by that industry standard, may have reheat but does
not require reheat. DOE requested comment on whether and how reheating
functionality should be included in the DDX-DOAS definition. 82 FR
34427, 34435-34436 (July 25, 2017).
In response to the July 2017 ASHRAE TP RFI, AHRI and Greenheck
commented that while capturing reheat performance in the test procedure
for DDX-DOAS equipment is an important aspect to many installations,
some building HVAC designs incorporating DDX-DOAS equipment operate
without any reheat capabilities. AHRI and Greenheck suggested that the
definition of DDX-DOAS should not require reheat, as it is important
for owners and designers to be able to select 100-percent outdoor air
units with varying amounts of reheat or no reheat. (AHRI, No. 11 at pp.
10-11, 20-21; Greenheck, No. 13 at p. 2) AHRI further commented that
DDX-DOAS design and optimum efficiency varies with climate and
application, and that the design is often customized to accommodate the
different needs of different applications. AHRI asserted that
regulations must allow for these differences to avoid increasing energy
consumption for a given project. (AHRI, No. 11 at p. 20-21) Greenheck
commented that the supplementary heat penalty included in ANSI/AHRI
920-2015 unfairly penalizes units without reheat, and Greenheck
suggested two options for rating units without reheat. (Greenheck, No.
13 at pp. 2-3). Carrier also commented that reheat functionality is an
application issue and is not applicable to the definition in a test
standard. (Carrier, No. 6 at p. 3)
DOE recognizes that the optimum-efficiency DDX-DOAS design varies
with climate and application. DOE also understands that the
supplementary heat penalty in ANSI/AHRI 920-2015 is not representative
of the way that units without reheat are used in the field. As is
discussed in section III.B.2.a of this document, as part of AHRI 920-
2020, AHRI modified the ISMRE metric to remove the supplementary heat
penalty in recognition that some installation conditions may not
require reheating. As is discussed in section III.B.1 of this document,
this metric was re-designated in AHRI 920-2020 as ISMRE2. AHRI 920-2020
also includes a separate application rating metric, ISMRE270, to
account for installations where reheating is required. Moreover, the
updated definition in AHRI 920-2020 recognizes that there are units
without reheat. As such, DOE is not proposing to include a reheat
requirement in the DX-DOAS or DDX-DOAS definition, consistent with AHRI
920-2020.
Because of the difference in terminology between the proposed DOE
test procedure and the relevant industry standards, DOE proposes to
include a section 2.3(a) in its proposed Appendix B indicating that the
different synonymous terms all refer to dehumidifying direct expansion-
dedicated outdoor air system as defined in 10 CFR 431.92.
Issue-3: DOE requests comment on its proposal to clarify what terms
are synonymous with DDX-DOAS.

B. Test Procedure for Dehumidifying Dedicated Outdoor Air Systems

Pursuant to EPCA, in response to the DDX-DOAS-related updates to
ASHRAE 90.1-2016 (maintained in ASHRAE 90.1-2019) and updates to the
industry test standard referenced in ASHRAE 90.1, DOE proposes to adopt
a test procedure for DDX-DOASes that incorporates by reference the
latest applicable industry consensus test standards.
In the following sections, DOE presents analysis and discussion of
several test procedure issues and proposes a test procedure for DDX-
DOASes. As discussed in more detail in the following sections, DOE has
initially determined that the proposed test procedure for DDX-DOASes
would be representative of an average use cycle and not be unduly
burdensome to conduct.
DOE is adopting the generally accepted industry testing procedures
for DDX-DOASes developed by AHRI (i.e., AHRI 920-2020) and referenced
by ASHRAE Standard 90.1, with the following modifications as discussed
in this NOPR:
[ssquf] Using the nomenclature DDX-DOAS, rather than DX-DOAS, to
define the equipment subject to the test procedure;
[ssquf] Defining an upper limit of capacity consistent with EPCA's
definition of very large commercial package air conditioning and
heating equipment;
[ssquf] Defining ``non-standard low-static fan motor,'' in order to
determine the appropriate airflow setting procedure;
[ssquf] Specifying the external head pressure requirements for
testing DDX-DOASes with integral water pumps;
[ssquf] Requiring that control settings remain unchanged for all
Standard Rating Conditions once system set-up has been completed prior
to testing;
[ssquf] Specifying requirements for testing equipment available
with multiple refrigerant options; and
[ssquf] Correcting a typographical error within one of the
equations.
1. Industry Consensus Test Standards
As first established in ASHRAE 90.1-2016, ASHRAE Standard 90.1-2019
specifies separate equipment classes for DDX-DOASes \13\ and sets
minimum

[[Page 36026]]

efficiency levels using the integrated seasonal moisture removal
efficiency (ISMRE) metric for all DDX-DOAS classes and also the
integrated seasonal coefficient of performance (ISCOP) metric for air-
source heat pump and water-source heat pump DDX-DOAS classes. ASHRAE
Standard 90.1-2019 specifies that both metrics are to be measured in
accordance with ANSI/AHRI Standard 920-2015, ``Performance Rating of
DX-Dedicated Outdoor Air System Units'' (ANSI/AHRI 920-2015). ANSI/AHRI
920-2015 specifies the method for testing DDX-DOASes, in part, through
a reference to ANSI/ASHRAE Standard 198-2013, ``Method of Test for
Rating DX-Dedicated Outdoor Air Systems for Moisture Removal Capacity
and Moisture Removal Efficiency'' (ANSI/ASHRAE 198-2013).
---------------------------------------------------------------------------

\13\ As discussed, the term DX-DOAS as defined by ASHRAE 90.1-
2019 is equivalent to the term DDX-DOAS as defined by DOE in this
NOPR.
---------------------------------------------------------------------------

ANSI/AHRI 920-2015 specifies Standard Rating Conditions (i.e.,
instructions on setting air and liquid flow rates, and equations for
calculating ISMRE and ISCOP). Table 2 and Table 3 of ANSI/AHRI 920-2015
provide outdoor and return air conditions for four Standard Rating
Conditions for the dehumidification test and two Standard Rating
Conditions for the heating test for heat pump DDX-DOASes. These tables
also provide condenser cooling water temperatures (for both cooling
tower and chilled water condensers) for water-cooled (cooling-only)
DDX-DOASes and water temperatures for water-source, ground-source
closed-loop, and ground-water source \14\ heat pump DDX-DOASes.
---------------------------------------------------------------------------

\14\ As discussed in section III.A.1 of this NOPR, the EPCA
definition for ``commercial package air conditioning and heating
equipment'' specifically excludes ground-water-source equipment (42
U.S.C. 6311(8)(A)). Accordingly, DOE is proposing to exclude this
equipment from the scope of applicability of the test procedure.
---------------------------------------------------------------------------

ANSI/ASHRAE 198-2013 includes requirements on instrumentation, test
set-up, tolerances, method of test, and calculations for moisture
removal capacity (MRC), moisture removal efficiency (MRE), heating
capacity (qhp) and heating coefficient of performance (COP). The MRE
for the dehumidification test is calculated for Standard Rating
Conditions \15\ A, B, C, and D of Table 2 or Table 3 of ANSI/AHRI 920-
2015 for air-cooled, water-cooled, and water-source heat pump DDX-
DOASes. Similarly, COP is calculated for the heating mode test for
Standard Rating Conditions E and F of Table 2 or Table 3 of ANSI/AHRI
920-2015 for heat pump DDX-DOASes. The MRE and COP values are
subsequently used to calculate ISMRE and ISCOP using weights that
correspond to temperature bin data for representative cities in the
United States.
---------------------------------------------------------------------------

\15\ Standard Rating Conditions in the AHRI 920 test procedure
represent full-load and part-load operating conditions for testing
DX-DOASes. Standard Rating Condition A represents full-load
operation in dehumidification mode, whereas Standard Rating
Conditions B-D represent part-load operation in dehumidification
mode. Standard Rating Condition F represents full-load operation in
heat pump mode at low temperatures, and Standard Rating Condition E
represents full-load operation in heat pump mode at high
temperatures.
---------------------------------------------------------------------------

DOE notes that AHRI recently revised AHRI 920 and published an
updated version on February 4, 2020, AHRI Standard 920-2020 (I-P),
``Performance Rating of Direct Expansion Dedicated Outdoor Air System
Units'' (AHRI 920-2020). AHRI 920-2020, which continues to reference
ANSI/ASHRAE 198-2013, includes revisions that DOE has initially
determined improve the representativeness, repeatability, and
reproducibility of the test methods while also reducing test burden.
These revisions include, among other things, the following: (1)
Expanded scope of coverage of the test procedure by no longer imposing
an upper limit of 97 lbs/hr on DDX-DOAS MRC, thereby making the test
procedure applicable to all DDX-DOASes subject to standards under
ASHRAE Standard 90.1; (2) revised outdoor air dry-bulb temperature
conditions, external static pressures, humidity conditions, and
weighting factors for ISMRE and ISCOP, which were redesignated as
ISMRE2 and ISCOP2, respectively; (3) revised calculations for achieving
the target supply air conditions for units with staged capacity
control; (4) added a supplementary cooling penalty when the supply air
dry-bulb temperature is greater than 75 [deg]F in dehumidification
mode; (5) removed a supplementary heat penalty for the efficiency
metric ISMRE2 when the supply air dry-bulb temperature is less than 70
[deg]F in dehumidification mode; \16\ (6) revised condenser water
conditions for water-cooled and water-source heat pump DDX-DOASes; (7)
added requirements for supply air dew point temperature; \17\ (8) added
requirements for outdoor coil liquid flow rate; (9) provided additional
test unit, test facility, instrumentation, and apparatus set-up
provisions; (10) revised test methods for DDX-DOASes equipped with
VERS; (11) added requirements for relief-air-cooled DDX-DOASes and DDX-
DOASes equipped with desiccant wheels; and (12) included requirements
for secondary capacity tests.
---------------------------------------------------------------------------

\16\ As discussed in section III.B.3.a of this NOPR, AHRI 920-
2020 additionally provides a method for calculating
ISMRE2<INF>70</INF>, an application metric for the dehumidification
efficiency with the inclusion of the supplementary heat penalty. The
subscript ``70'' indicates the inclusion of energy use from any
supplementary heat that is required to raise the supply air dry bulb
temperature to 70 [deg]F.
\17\ Dew point is the temperature below which water begins to
condense from the water vapor state in humid air into liquid water
droplets. Dew point varies with humidity (e.g., a low dew point
indicates low humidity and vice versa) and is, therefore, used to
specify the humidity of the supply air.
---------------------------------------------------------------------------

DOE carefully reviewed both ANSI/AHRI 920-2015 and ANSI/ASHRAE 198-
2013, as well as the latest changes in AHRI 920-2020, in consideration
of this NOPR. In the following sections, DOE discusses the proposed
definition for DDX-DOASes, scope of the test procedure, efficiency
metrics, test methods (including the updates to AHRI 920 in the 2020
version listed in the prior paragraph), and sampling requirements.
Generally, DOE incorporates industry standards into the regulations by
reference to the standard. In this NOPR, DOE has proposed to
incorporate by reference AHRI 920-2020.
DOE is also proposing to incorporate by reference several industry
standards that are referenced by AHRI 920-2020, as shown in Table III-
1.

Table III-1--Additional Industry Standards Proposed To Be Incorporated
by Reference
------------------------------------------------------------------------
Section(s) in AHRI 920-2020
Industry standard that reference this industry
standard
------------------------------------------------------------------------
ANSI/ASHRAE 198-2013...................... Section 5; Section 6;
Appendix C.
ANSI/ASHRAE 37-2009....................... Section 5; Section 6;
Appendix C.
ANSI/ASHRAE 1060-2018..................... Section C4.
ANSI/ASHRAE 41.1-2013..................... Section C3.3.1.
ANSI/ASHRAE 41.6-2014..................... Section C3.1.3.2.
------------------------------------------------------------------------

In response to the July 2017 ASHRAE TP RFI, AHRI commented that the
ISMRE and ISCOP levels specified for DDX-DOASes in ASHRAE 90.1-2016
will need adjustment if changes to the test procedure negatively impact
these values (AHRI, No. 11 at p. 20).
This NOPR proposes to incorporate by reference the latest version
of the industry test procedure for DDX-DOASes which is recognized by
ASHRAE Standard 90.1: AHRI 920 (the latest version being AHRI 920-
2020). When the test procedures referenced in ASHRAE Standard 90.1 are
updated, EPCA requires DOE to amend the Federal test procedures for
such covered ASHRAE equipment (which manufacturers are required to use
in order to certify compliance with energy

[[Page 36027]]

conservation standards mandated under EPCA) to be consistent with the
amended industry consensus test procedure. (42 U.S.C. 6314(a)(4)(B))
The energy efficiency standards specified in ASHRAE Standard 90.1
are based on ANSI/AHRI 920-2015 and ANSI/ASHRAE 198-2013. However, the
amendments adopted in AHRI 920-2020 result in changes to the measured
efficiency metrics as compared to the results under ANSI/AHRI 920-2015.
As discussed, DOE has not established in its regulations energy
conservation standards specifically for DDX-DOASes. DOE will address
any potential differences in the measured energy efficiency under the
most recent industry test procedure as compared to the industry test
procedure on which the ASHRAE Standard 90.1 levels are based at such
time as DOE evaluates the ASHRAE Standard 90.1 levels for DDX-DOASes
(i.e., by developing an appropriate crosswalk, as necessary).
Specifically, DOE intends to request that DDX-DOAS manufacturers
provide any data and/or analysis that indicates whether and how much
the measured rating of DDX-DOASes would be expected to change under the
most recent version of the industry consensus test standard.
Issue-4: DOE requests comment and data on the development of a
crosswalk from the efficiency levels in ASHRAE Standard 90.1 based on
ANSI/AHRI 920-2015 to efficiency levels based on AHRI 920-2020. DOE is
specifically seeking data on how dehumidification and heating
efficiency ratings for a given DDX-DOAS model are impacted when
measured using AHRI 920-2020 as compared to ANSI/AHRI 920-2015.
2. Efficiency Metrics
a. Dehumidification Metric
ASHRAE 90.1-2016 adopted a dehumidification efficiency metric for
DDX-DOASes. Specifically, ASHRAE 90.1-2016 uses ISMRE, as presented in
section 3.10 of ANSI/AHRI 920-2015, as a seasonal efficiency metric
calculated as a weighted average of MRE for four different
dehumidification rating conditions. MRE for each test condition is the
MRC for that condition divided by electric power input, including
consideration of electric resistance reheat if needed to raise supply
air temperature to 70 [deg]F (i.e., ``supplementary heat''). MRC
represents the rate at which the DDX-DOAS removes humidity from the air
in pounds of moisture per hour. As discussed further in section
III.B.2.c of this document, AHRI indicated that the seasonal weighting
factors for determining ISMRE, as specified in ANSI/AHRI 920-2015, were
developed based on climate data from a sample of twelve cities chosen
to be representative of a wide range of climatic data in the United
States.
The primary function of DDX-DOASes is to provide conditioned
(cooled and dehumidified, or heated) outdoor air. In the cooling/
dehumidifying season, these units provide sensible cooling that reduces
the temperature of the outdoor air in addition to dehumidifying. DOE
noted in the July 2017 ASHRAE TP RFI that the ISMRE metric specified in
ANSI/AHRI 920-2015 does not include any provisions to measure the
sensible cooling contribution provided by the DDX-DOAS. 82 FR 34427,
34436 (July 25, 2017). For Standard Rating Conditions A and B in Table
2 and Table 3 of ANSI/AHRI 920-2015, conditioning the air to a space
temperature (70 [deg]F) requires sensible cooling as well as latent
cooling. In the July 2017 ASHRAE TP RFI, DOE requested comment on
whether the DDX-DOAS efficiency metric should account for this sensible
cooling. 82 FR 34427, 34436 (July 25, 2017).
In response to the July 2017 ASHRAE TP RFI, AHRI commented that
DDX-DOASes operate with a separate, sensible-cooling-only interior
cooling system, and that adding sensible cooling to the metric for DDX-
DOAS would skew efficiency values toward the non-primary function of
the DDX-DOAS. AHRI also stated that the capacity for sensible cooling
varies between DDX-DOAS designs, so the use of space-neutral air \18\
gives a worst-case efficiency to be used as comparison. (AHRI, No. 11
at p. 12) Carrier expressed concern that the current metric focuses on
latent capacity and that a shortcoming of the test procedure is that it
does not consider sensible capacity. Carrier also stated that
considering only latent capacity would be acceptable if the unit
delivers space-neutral air, but some DDX-DOASes can provide sensible
cooling. (Carrier, No. 6 at p. 3)
---------------------------------------------------------------------------

\18\ Space-neutral air, or neutral air, refers to air leaving an
air conditioner being at the target conditions for the occupied
space in the building (without the need for subsequent sensible or
latent cooling).
---------------------------------------------------------------------------

As discussed in section III.B.2.c of this NOPR, DOE proposes to
incorporate by reference the dehumidification metrics contained in the
updated version of the industry consensus standard, AHRI 920-2020. DOE
notes that the revised dehumidification metric in AHRI 920-2020,
ISMRE2, does not include provisions to determine the sensible cooling
contribution in the metric. However, as discussed in section III.B.1 of
this document, the ISMRE2 metric, which is specified in AHRI 920-2020
as the required rating metric for dehumidification efficiency, removes
the supplementary heat penalty to avoid penalizing DDX-DOAS units that
provide sensible cooling below 70 [deg]F.
DOE recognizes that the sensible cooling provided by a DDX-DOAS
unit may be valuable in many applications because it reduces the
cooling that must be provided by interior cooling systems, especially
at high outdoor temperatures. However, for certain applications it may
be important to reheat the supply air to balance the building's
sensible cooling load.\19\ DOE may consider in a future rulemaking
whether the efficiency metric should be revised to include sensible
cooling, if information is made available to support such a change.
---------------------------------------------------------------------------

\19\ As discussed in section III.B.1 of this document, AHRI 920-
2020 include separate application metrics (i.e., ISMRE270) to be
used for additional representations and that are calculated with a
supplementary heat penalty based on raising the supply air dry-bulb
temperature up to 70 [deg]F.
---------------------------------------------------------------------------

ASHRAE Standard 90.1-2016 uses ISMRE (using ANSI/AHRI 920-2015) as
the metric for the specified minimum efficiencies for DDX-DOAS. As
discussed in section III.B.1 of this NOPR, DOE is aware that updates to
the industry test procedure in AHRI 920-2020 using ISMRE2 could impact
the measured efficiencies of DDX-DOASes as compared to ISMRE measured
in accordance with ANSI/AHRI 920-2015, thereby necessitating use of an
appropriate crosswalk analysis. Therefore, DOE will address these
potential impacts on the measured efficiencies in a separate standards
rulemaking.
b. Heating Metric
ASHRAE 90.1-2016 adopted ISCOP, as presented in ANSI/AHRI 920-2015,
as the heating efficiency metric, and it also set minimum ISCOP
efficiency levels for both air-source and water-source heat pump DDX-
DOASes. ISCOP is a seasonal energy efficiency metric and is calculated
as the seasonal weighted average of heating COPs determined for two
heating Standard Rating Conditions specified in Table 2 and Table 3 of
ANSI/AHRI 920-2015.
In the July 2017 ASHRAE TP RFI, DOE noted that although the
Department has identified air-source heat pump DDX-DOASes available on
the market, section 3.9 of ANSI/AHRI 920-2015 defines ISCOP as an
energy efficiency metric only for water-source heat pump DDX-DOASes. 82
FR 34427, 34436 (July 25, 2017). DOE also noted

[[Page 36028]]

in the July 2017 ASHRAE TP RFI that equations in section 10.9 of ANSI/
ASHRAE 198-2013 for calculating the COP are labeled for application to
water-source heat pump DDX-DOASes, although DOE once again noted that
they could be applied to air-source heat pump DDX-DOASes. Id. As part
of the July 2017 ASHRAE TP RFI, DOE requested comment on the
calculation procedure for COP for air-source heat pumps, including
whether the equations in ANSI/ASHRAE 198-2013 are applicable to air-
source heat pumps. Id. DOE did not receive any comments on this topic.
Because ASHRAE Standard 90.1-2016 specifies minimum efficiency levels
for both air-source and water-source heat pump DDX-DOASes using ANSI/
AHRI 920-2015, DOE considers the ISCOP and COP calculations to be
applicable to the minimum efficiency levels in ASHRAE Standard 90.1-
2016 for both equipment classes.
In further clarification, AHRI 920-2020 revised the definition of
``Direct Expansion-Dedicated Outdoor Air System Units'' and the heating
efficiency metric (designated as ISCOP2) to include both air-source and
water-source heat pump DDX-DOASes. The ISCOP2 metric specified in
section 3.13 of AHRI 920-2020 also includes revisions to the outdoor
air conditions, weighting factors, and treatment of heating capacity
calculations. DOE is proposing to adopt ISCOP2 as the heating
efficiency metric for DDX-DOASes under the DOE test procedure,
expressed in Watts (W) of heating capacity per W of power input. As
discussed in section III.B.1 of this NOPR, updates to the industry
consensus test procedure in AHRI 920-2020 using ISCOP2 could impact the
measured heating efficiencies of DDX-DOASes as compared to ISCOP
measured in accordance with ANSI/AHRI 920-2015, thereby necessitating
use of an appropriate crosswalk analysis. Therefore, DOE will address
these potential impacts on the measured heating efficiencies in a
separate standards rulemaking.
ISCOP2 is calculated using COPISCOP values for Standard Rating
Conditions E and F that apply a supplementary heat penalty to the total
power input if the supply air dry-bulb temperature is less 70 [deg]F.
Section 6.11 of AHRI 920-2020 includes additional application rating
heating metrics, COP<INF>full</INF> and COP<INF>DX-DOAS</INF>, for
additional representations. COP<INF>DX-DOAS</INF> is calculated without
a supplementary heat penalty, while COP<INF>full</INF> is used for
manufacturer-specified outdoor conditions. DOE is proposing in section
2.2.2 of Appendix B to allow COP<INF>full</INF> and
COP<INF>DX-DOAS</INF> to be used by manufacturers for voluntary
representations.
c. ISMRE2 and ISCOP2 Weighting Factors
As part of the July 2017 ASHRAE TP RFI, DOE requested information
about analysis of climate data relevant to the development of the ISMRE
and ISCOP test conditions and weighting factors. 82 FR 34427, 34436
(July 25, 2017). AHRI commented that the values and weightings for both
the dehumidification and heating points in ANSI/AHRI 920-2015 were
developed based on climatic data for a sample of twelve cities \20\
chosen to be representative of a wide range of climatic conditions in
the United States. According to AHRI, the climatic bin data were based
on 24-hour operation per day due to the variety of applications where
DDX-DOASes are installed and provide a reasonable standard for
assessing the part-load situations that will be encountered. (AHRI, No.
11 at p. 12) DOE notes that these test conditions in ANSI/AHRI 920-2015
were established to represent specific regions of the psychrometric
chart, as shown in the following Table III-2 and Table III-3.
---------------------------------------------------------------------------

\20\ The sample of 12 cities analyzed were: New York City,
Atlanta, Chicago, El Paso, Houston, Kansas City, Miami, Minneapolis,
Nashville, New Orleans, Norfolk, and Tucson.
---------------------------------------------------------------------------

In the development of AHRI 920-2020, DOE provided input on weather
data, and AHRI also reviewed Typical Meteorological Year (TMY) 2 \21\
weather data from the National Renewable Energy Laboratory. Based, in
part, on this input and data, AHRI 920-2020 specifies the ISMRE2 and
ISCOP2 test conditions and weighting factors, which represent the
number of hours per year for each test condition. Accordingly, Table
III-2 and Table III-3 also show the Standard Rating Conditions and
weighting factors included in sections 6.1, 6.12, and 6.13 of AHRI 920-
2020. DOE is proposing to adopt the weighting factors for the ISMRE2
(including the test conditions specific for ISMRE2<INF>70</INF>) and
ISCOP2 metrics, as specified in AHRI 920-2020.
---------------------------------------------------------------------------

\21\ TMY stands for ``typical meteorological year'' and is a
widely used type of data available through the National Solar
Radiation Database. TMYs contain one year of hourly data that best
represents median weather conditions over a multiyear period. The
datasets have been updated occasionally, thus TMY, TMY2, and TMY3
data are available. See <a href="http://nsrdb.nrel.gov/about/tmy.html">nsrdb.nrel.gov/about/tmy.html</a> (last accessed
4/28/21).

Table III-2--ANSI/AHRI 920-2015 and AHRI 920-2020 Dehumidification Mode Standard Rating Conditions and ISMRE/
ISMRE2/ISMRE270 Weighting Factors
----------------------------------------------------------------------------------------------------------------
ANSI/AHRI 920-2015 AHRI 920-2020
--------------------------------------------------------------------
Standard rating Psychrometric chart Representative Representative ISMRE2 and
condition region represented condition (dry-bulb ISMRE condition (dry-bulb ISMRE270
temperature/ wet- weighting temperature/ wet- weighting
bulb temperature) factor bulb temperature) factor
----------------------------------------------------------------------------------------------------------------
A................ Above 55 [deg]F dew 95 [deg]F/78 [deg]F 12 95 [deg]F/78 [deg]F 14
point, Above 75 [deg]F
wet-bulb.
B................ Above 55 [deg]F dew 80 [deg]F/73 [deg]F 28 80 [deg]F/73 [deg]F 34
point, >69 [deg]F and
<=75 [deg]F wet-bulb.
C................ Above 55 [deg]F dew 68 [deg]F/66 [deg]F 36 70 [deg]F/66 [deg]F 39
point, >62 [deg]F and
<=69 [deg]F wet-bulb.
D................ Above 55 [deg]F dew 60 [deg]F/58 [deg]F 24 63 [deg]F/59 [deg]F 13
point, >56 [deg]F and
<=62 [deg]F wet-bulb.
----------------------------------------------------------------------------------------------------------------

[[Page 36029]]

Table III-3--ANSI/AHRI 920-2015 and AHRI 920-2020 Heating Mode Standard Rating Conditions and ISCOP/ISCOP2
Weighting Factors
----------------------------------------------------------------------------------------------------------------
ANSI/AHRI 920-2015 AHRI 920-2020
-------------------------------------------------------------------
Standard rating Psychrometric chart Representative Representative
condition region represented condition (dry-bulb ISCOP condition (dry-bulb ISCOP2
temperature/ wet- weighting temperature/ wet- weighting
bulb temperature) factor bulb temperature) factor
----------------------------------------------------------------------------------------------------------------
E................. Below 55 [deg]F dew 35 [deg]F/29 [deg]F 77 47 [deg]F/43 [deg]F 91
point, >23 [deg]F and
<=64 [deg]F dry-bulb.
F................. Below 55 [deg]F dew 16 [deg]F/12 [deg]F 23 17 [deg]F/15 [deg]F 9
point, <=23 [deg]F dry-
bulb.
----------------------------------------------------------------------------------------------------------------

3. Test Method
This section discusses the various issues that DOE identified in
the industry consensus test standards applicable to DDX-DOASes,
including those raised in the July 2017 ASHRAE TP RFI and considered as
part of DOE's review of AHRI 920-2020. These issues include: (1)
Definitions for certain terms used in the DDX-DOAS test procedure; (2)
optional break-in period for DDX-DOASes; (3) test facility,
instrumentation, and apparatus set-up issues; (4) DDX-DOAS unit set-up;
(5) test operating conditions; (6) requirements for water-cooled and
water-source heat pump DDX-DOASes; (7) defrost energy use; (8) test
methods for DDX-DOASes equipped with VERS; (9) tolerances; and (10)
secondary verification tests for dehumidification and heating tests.
Table 1 to 10 CFR 431.96 specifies the applicable industry test
procedure for each category of commercial package air conditioning and
heating equipment and specifies any additional testing requirements
that may also apply. In this NOPR, DOE is proposing to add test
procedure requirements for DDX-DOASes in a separate appendix in subpart
F to 10 CFR part 431 (i.e., proposed Appendix B). Accordingly, DOE
proposes to include DDX-DOASes in Table 1 to 10 CFR 431.96 and to
reference Appendix B for the DDX-DOASes test procedure.
a. Definitions
Section 3 of AHRI 920-2020 and section 3 of ANSI/ASHRAE 198-2013
define terms used in the industry consensus test standards for DDX-
DOASes. DOE reviewed these sections and is proposing generally to adopt
the definitions in section 3 of AHRI 920-2020 (as enumerated in section
2.2.1(a) of proposed Appendix B). As discussed, DOE is proposing
definitions in the test procedure provisions for ``direct expansion-
dedicated outdoor air system, or DX-DOAS'' as a category of commercial
package air conditioning and heating equipment, and ``dehumidifying
direct expansion-dedicated outdoor air system, or DDX-DOAS,'' as a
subset of DX-DOAS.
As discussed in the following paragraphs DOE is also proposing to
define ``integrated seasonal coefficient of performance 2, or ISCOP2,''
``integrated seasonal moisture removal efficiency 2, or ISMRE2,'' and
``ventilation energy recovery system, or VERS.'' In section 1.1 of
Appendix B, DOE proposes to provide that where any definitions conflict
between AHRI 920-2020 (or any of the industry standards referenced) and
the CFR, the CFR provisions control.
DOE notes that 10 CFR 431.92 includes definitions for the
efficiency metrics used for commercial package air conditioners and
heat pumps. Consistent with this approach, DOE is proposing definitions
at 10 CFR 431.92 for ``integrated seasonal coefficient of performance
2, or ISCOP2'' and ``integrated seasonal moisture removal efficiency 2,
or ISMRE2'' that are consistent with the definitions for these metrics
defined in sections 3.12 and 3.13 of AHRI 920-2020 and that
specifically reference the DDX-DOAS test procedure in proposed Appendix
B.
A ``ventilation energy recovery system'' (VERS) pre-conditions the
outdoor air before it enters the conditioning coil, thereby reducing
the cooling, dehumidification, or heating load on the refrigeration
system of the DDX-DOAS. ASHRAE Standard 90.1-2019 specifies separate
equipment classes and minimum efficiency levels for DDX-DOASes with
VERS equipment. DOE notes that neither a definition for a VERS nor a
different term for this system is included in the previous test
standards ANSI/AHRI 920-2015 and ANSI/ASHRAE 198-2013. However, AHRI
920-2020 does include a definition for VERS. DOE proposes, consistent
with AHRI 920-2020, to define a VERS as a system that preconditions
outdoor ventilation air entering the equipment through direct or
indirect thermal and/or moisture exchange with the exhaust air, which
is defined as the building air being exhausted to the outside from the
equipment.
A VERS may also be used by commercial air-conditioning equipment
other than DDX-DOASes. However, for commercial air-conditioning
equipment other than DDX-DOASes, neither ASHRAE Standard 90.1-2019 nor
the DOE energy conservation standards establish equipment classes based
on the presence of VERS. Under the DOE test procedures for commercial
package air conditioners and heat pump equipment other than DDX-DOASes,
VERS is a feature that is not installed for testing. Because an
understanding of VERS may be relevant to commercial package air
conditioners and heat pumps other than the proposed DDX-DOAS category
of equipment, DOE is proposing to establish a definition of VERS,
consistent with AHRI 920-2020, in 10 CFR 431.92 so that it is broadly
applicable when used in reference to both DDX-DOASes as well as other
commercial package air conditioning and heat pump equipment.
Additionally, DOE is proposing to amend the definition of
``commercial HVAC & WH product'' at 10 CFR 431.2 to explicitly include
DDX-DOAS.
Issue-5: DOE requests comment on the terminology DOE proposes to
use for DDX-DOASes, including ``integrated seasonal coefficient of
performance 2, or ISCOP2;'' ``integrated seasonal moisture removal
efficiency 2, or ISMRE2;'' and ``ventilation energy recovery system, or
VERS.''
In the July 2017 ASHRAE TP RFI, DOE sought clarification on the
difference between a reheat system and supplementary heat in ANSI/AHRI
920-2015 and ANSI/ASHRAE 198-2013. 82 FR 34427, 34436 (July 25, 2017).
The definition for supplementary heat provided in section 3.21 of ANSI/
AHRI 920-2015 does not state whether it includes heat provided by
reheat systems such as wrap-around heat pipes and wrap-around vapor
compression systems.
In response to the July 2017 ASHRAE TP RFI, AHRI suggested a
revised definition for ``supplementary heat'' that

[[Page 36030]]

excludes heat provided by the vapor compression cycle or a sub-system
that transfers heat from one part of the unit to another (e.g., wrap-
around heat pipe, wrap-around vapor compression system). (AHRI, No. 11
at p. 11)
DOE notes that section 3.25 of AHRI 920-2020 has clarified this
issue by defining ``supplementary heat'' to exclude a system that
transfers heat from the outdoor air to the supply air. The AHRI 920-
2020 definition distinguishes reheat provided by a vapor compression
cycle that is driving the dehumidification process from common
supplementary heat options such as fuel-fired heating, steam or hot
water heating coils, and electric resistance. Further, section 3.25 of
AHRI 920-2020 also states that reheat provided by secondary heat pumps,
wrap around heat pumps, or wrap around heat pipes are not considered as
supplementary heat. As discussed, DOE proposes to adopt the definition
for ``supplementary heat'' provided in section 3.25 of AHRI 920-2020,
as enumerated in section 2.2.1(a) of the proposed Appendix B, which
references section 3 of AHRI 920-2020.
b. Break-In Period
As part of the DOE test procedures for other commercial package air
conditioners and heat pumps, DOE provides the option for a ``break-in''
period, not to exceed 20 hours, with no ambient temperature
requirements, prior to performing a test. See 10 CFR 431.96(c). This is
intended to allow the unit to achieve optimal performance prior to the
test. Neither ANSI/AHRI 920-2015 nor ANSI/ASHRAE 198-2013 specify a
break-in period for testing DDX-DOASes. In response to the July 2017
ASHRAE TP RFI, AHRI commented that proper compressor break-in must be
allowed to provide a fair and accurate test. AHRI also stated that it
had previously submitted comments that 16 hours is not sufficient.
(AHRI, No. 11 at p. 20)
DOE addressed comments previously submitted by AHRI that DOE should
require a minimum 16-hour break-in period for all commercial air
conditioning equipment as part of the rulemaking finalized in a May 16,
2012 final rule for energy conservation standards and test procedures
for commercial heating, air-conditioning, and water-heating equipment.
77 FR 28928, 28943. As part of that final rule, DOE determined that
adopting a minimum break-in period of 16 hours would unnecessarily
increase testing costs for manufacturers of equipment that can achieve
stability in less than 16 hours. In recognition that different
equipment will require different amounts of break-in time to achieve
optimal performance and that break-in periods of longer than 16 hours
may be required for some equipment, DOE adopted an optional break-in
period up to a maximum period of 20 hours to allow the unit to achieve
optimal performance before testing for commercial air conditioning and
heating equipment. 77 FR 28928, 28943-28944 (May 16, 2012). Section 5.6
of AHRI 920-2020 incorporates the same break-in period provision, not
to exceed 20 hours. Therefore, DOE proposes to adopt the optional
break-in period up to a maximum of 20 hours for DDX-DOASes specified in
AHRI 920-2020 (section 5.6 Break-in), as enumerated in section 2.2.1(b)
of the proposed Appendix B, which references section 5 of AHRI 920-
2020.
c. Airflow-Measuring Apparatus
Figures 1 and 2 of ANSI/ASHRAE 198-2013 present the typical test
set-up for DDX-DOASes with and without energy recovery. The figures
show airflow and condition measuring apparatus at both the inlet and
the outlet ends of each airflow path (i.e., the outdoor/supply and
return/exhaust paths). DOE stated in the July 2017 ASHRAE TP RFI that
it is not clear whether airflow-measuring apparatus are required for
both entering and leaving air of each airflow path. 82 FR 34427, 34439
(July 25, 2017). DOE requested comment on whether it is beneficial or
necessary to use two airflow-measuring apparatus per airstream when
testing DDX-DOAS equipment. Id.
AHRI and Carrier both commented that using two airflow devices per
airstream would be difficult and costly due to challenges with space
constraints, additional physical barriers that can increase temperature
stratification in the test chamber, and issues associated with meeting
the specified design conditions due to fan reheat energy in the airflow
measuring stations. (AHRI, No. 11 at p. 19; Carrier, No. 6 at p. 7)
AHRI further commented that while additional airflow measuring stations
have the benefit of monitoring cross-leakage or general leakage in the
cabinet, it makes testing difficult, if not impossible, to perform.
(AHRI, No. 11 at p. 19) None of the commenters indicated that use of
two airflow-measuring apparatus per airflow path is necessary to obtain
accurate measurements.
Based on comments from AHRI and Carrier, DOE tentatively concludes
that requiring two airflow-measuring apparatus per airflow path may be
unduly burdensome for certain manufacturers. However, DOE also
recognizes that the additional measurements may provide an indication
of crossflow and/or leakage. DOE has tentatively concluded that AHRI
920-2020 offers a more suitable approach to airflow measurement, for
the reasons that follow. Section C2.2 of AHRI 920-2020 requires just
one airflow-measuring apparatus per airflow path. To provide a check
for general cabinet leakage, section C5.1 of AHRI 920-2020 specifies a
methodology for performing a secondary capacity measurement that does
not require a second airflow-measuring apparatus (rather, the
methodology for verifying dehumidification capacity is based on a
measurement of the weight of collected condensate). The requirement for
just one airflow-measuring apparatus per airflow path is consistent
with the DOE test procedures for all other commercial and residential
air-conditioning and heating systems and limits the testing costs and
burden on manufacturers.
Regarding the commenters' concern that the fan heat of the airflow-
measuring apparatus might affect the controlled air conditions, DOE
recognizes that this could affect the temperature of the return air
entering the DDX-DOAS under test. A similar issue could occur when
duct-inlet booster fans are used for moving outdoor air either to the
outdoor ventilation air inlet from a separate room, or when moving
desiccant regeneration air from another room. On this topic, section
C3.2.2 of AHRI 920-2020 specifies that in such circumstances, the air
conditions are to be measured downstream of the fan and that the
sampled air used for the air condition measurement be returned: (a) To
a location between the flow nozzles and the fan of a return airflow-
measuring apparatus, or (b) to the separate room from which air is
drawn when a boost fan is used in the inlet duct. Accordingly, in this
NOPR, DOE is proposing to adopt the provisions for the airflow-
measuring apparatus specified in AHRI 920-2020 section C2.2, ``Use of a
Single Airflow Rate Measuring Apparatus per Airflow Path'' in Appendix
C of AHRI 920-2020 (rather than the dual measurement apparatus
specifications in Figures 1 and 2 of ANSI/ASHRAE 198-2013), as
enumerated in section 2.2.1(f) of the proposed Appendix B, which
references Appendix C of AHRI 920-2020.
d. Test Operating Conditions
Through incorporation by reference of AHRI 920-2020, DOE is
proposing to adopt the test operating conditions

[[Page 36031]]

specified in AHRI 920-2020 for DDX-DOAS units. These include: (1)
Standard Rating Conditions (Tables 4 and 5 of section 6 of AHRI 920-
2020, as enumerated in section 2.2.1(c) of the proposed Appendix B,
which references section 6 of AHRI 920-2020 omitting sections 6.1.2 and
6.6.1); (2) simulated ventilation air conditions for testing under
Option 2 for DDX-DOASes with VERS (section 5 of AHRI 920-2020 (which
includes section 5.4.1.2 Option 2), as enumerated in section 2.2.1(b)
of the proposed Appendix B, which references section 5 of AHRI 920-
2020); (3) atmospheric pressure (section 5 of AHRI 920-2020 (which
includes section 5.10 Atmospheric Pressure), as enumerated in section
2.2.1(b) of the proposed Appendix B); (4) target supply air conditions
(section 6 of AHRI 920-2020 (which includes section 6.1.3 Supply Air
Dewpoint Temperature and section 6.1.4 Supply Air Dry Bulb
Temperature), as enumerated in section 2.2.1(c) of the proposed
Appendix B); (5) external static pressure (section 6 of AHRI 920-2020
(which includes section 6.1.5.6 External Static Pressure), as
enumerated in section 2.2.1(c) of the proposed Appendix B); and (6)
target supply and return airflow rates (section 6 of AHRI 920-2020
(which includes section 6.1.5 Supply and Return Airflow Rates), as
enumerated in section 2.2.1(c) of the proposed Appendix B).
DOE received comments from interested parties regarding target
supply and return airflow rates and target supply air conditions in
response to the July 2017 ASHRAE TP RFI, and the following section
discusses these specific issues.
i. Target Supply and Return Airflow Rates
Section 5.2.2 of ANSI/AHRI 920-2015 and section 8.1 of ANSI/ASHRAE
198-2013 require the supply airflow rate to be set in accordance with
manufacturer specifications. In the July 2017 ASHRAE TP RFI, DOE
observed that many DDX-DOAS models are capable of operating over a
range of airflow rates. 82 FR 34427, 34437 (July 25, 2017). DOE expects
these models to have supply air fans that can be configured with a
range of speeds to accommodate the airflow range and the variation in
duct length in field installations. Id. The performance of these models
may also vary significantly from the low end to the high end of the
specified airflow range. As part of the July 2017 ASHRAE TP RFI, DOE
sought comments on how manufacturers select the airflow rate for
testing, given the large range of airflows that are typical of DDX-DOAS
units. Id.
In response to this issue, AHRI commented that the optimum-
efficiency airflow varies with each application and that the
manufacturer should specify the design airflow rate as long as it
achieves the 55 [deg]F dew point temperature. (AHRI, No. 11 at pp. 13-
14) The approach described by AHRI is consistent with the approach of
AHRI 920-2020, which stipulates the use of the manufacturer-specified
airflow in section 6.1.5 of that document. This section of AHRI 920-
2020 also addresses how to set the airflow when it is not specified by
the manufacturer and the case where the dehumidification provided is
not consistent with DDX-DOAS performance (i.e., provision of supply air
at 55 [deg]F or lower dew point, when using the manufacturer-specified
airflow).\22\
---------------------------------------------------------------------------

\22\ Section 6.1.3 of AHRI 920-2020 includes an adjustment for
maximum supply air dew point temperature to increase linearly as
barometric pressure decreases, up to 57.3 [deg]F at the minimum-
allowed 13.7 psia test pressure.
---------------------------------------------------------------------------

As discussed, DOE is proposing to adopt the provisions in section
6.1.3 and 6.1.5 of AHRI 920-2020, which specify that the target supply
airflow rate be the manufacturer-specified airflow rate and that, for
Standard Rating Condition A, achieves dehumidification consistent with
providing a 55 [deg]F dew point temperature in standard atmospheric
pressure conditions. In cases where supply airflow is not specified by
the manufacturer, or supply air dew point exceeds the maximum when
using the manufacturer-specified airflow, AHRI 920-2020 requires
setting airflow for Standard Rating Condition A such that the supply
air dew point does not exceed the maximum.
ii. Units With Cycle Reheat Functions
As part of the July 2017 RFI, DOE noted that provisions regarding
reheat and the supplementary heat penalty specified in ANSI/AHRI 920-
2015 and ANSI/ASHRAE 198-2013 were unclear. 82 FR 34427, 34436 (July
25, 2017). Most of the DDX-DOAS models that are equipped with the
capability to reheat dehumidified air to space-neutral conditions use
hot refrigerant gas discharged by the compressor to reheat the
dehumidified air leaving the evaporator coil. Other approaches can also
be used to transfer heat from one part of the DDX-DOAS to another.
(Section 3.21.1 of AHRI 920-2020 defines all of these methods as
``cycle reheat.'') Reheat may also be provided by supplementary heat
sources, such as a gas furnace or an electric resistance heater, but
these are not considered cycle reheat. A discussion of cycle reheat
capability with respect to the scope of this test procedure is provided
in section III.A.4 of this document, and a discussion of the
supplementary heat penalty is provided in section III.B.3.a of this
document.
ANSI/AHRI 920-2015 requires that supply air dew point temperature
be 55 [deg]F or lower, which generally means (i.e., for a DDX-DOAS that
removes moisture by latent cooling without the use of desiccants) that
the air must be cooled to a temperature that is, at most, a few degrees
above 55 [deg]F. Section 6 of ANSI/AHRI 920-2015 does not explicitly
require testing with reheat turned on, but note 3 to Table 2 and note 3
to Table 3 of that industry standard require the DDX-DOAS to condition
supply air to a minimum dry-bulb temperature of 70 [deg]F for all
dehumidification and heating tests--and this would have to be
accomplished with active reheat (as discussed in the following
paragraphs). Further, for units unable to meet this minimum threshold,
section 6.1.3.1 of ANSI/AHRI 920-2015 specifies the application of a
supplementary heat penalty to represent the power input that would be
required to heat the supply air to the 70 [deg]F target using electric
resistance heating.
DOE noted in the July 2017 RFI that ANSI/ASHRAE 198-2013 includes
two dehumidification tests, one with cycle reheat functions turned on
and the other with cycle reheat functions turned off (sections 8.3.1.1
and 8.3.1.2, respectively). DOE further noted that ANSI/AHRI 920-2015
does not, however, specify which of these values is used in the
calculation of ISMRE. 82 FR 34427, 34436 (July 25, 2017).
As part of the July 2017 ASHRAE TP RFI, DOE requested comment on
whether the dehumidification test with cycle reheat on or off should be
used to calculate ISMRE, and how and when the supplementary heat
penalty is applied. 82 FR 34427, 34436 (July 25, 2017). AHRI commented
that the dehumidification efficiency metrics specified in ANSI/AHRI
920-2015 are based on supply air at a dry-bulb temperature of 70
[deg]F, and if the unit requires reheat to be on (as described in ANSI/
ASHRAE 198-2013) for supply air temperature control, then this reheat-
on test is needed to determine dehumidification capacity and
efficiency. (AHRI, No. 11 at p. 11) DOE understands AHRI's comment to
mean that ANSI/AHRI 920-2015 effectively requires cycle reheat to be
activated during dehumidification tests in order to meet both the
supply air dew point and dry-bulb temperature requirements.
In contrast to ANSI/AHRI 920-2015, AHRI 920-2020 more explicitly

[[Page 36032]]

addresses the use of cycle reheat for dehumidification tests and
provides more information on when the supplementary heat penalty should
be used. As discussed in section III.B.2.a of this NOPR, DOE is
proposing to adopt the revised MRE and ISMRE2 metrics specified in AHRI
920-2020, which do not include a supplementary heat penalty. Section
6.1.4.2 of AHRI 920-2020 specifies that when determining MRE and
ISMRE2, the manufacturer shall specify whether cycle reheat is to be
activated for the test. As discussed in section III.B.2.a of this
document, AHRI 920-2020 provides separate application metrics (i.e.,
MRE<INF>70</INF> and ISMRE2<INF>70</INF>) which may be used for
representations and which require a supply air dry-bulb temperature
above 70 [deg]F (and below 75 [deg]F). For these separate application
metrics, if cycle reheat cannot achieve 70 [deg]F, a supplementary heat
penalty is applied based on raising the supply air dry-bulb temperature
up to 70 [deg]F (see section 6.1.4.1 of AHRI 920-2020). DOE has
tentatively determined that these provisions in AHRI 920-2020 clarify
the requirements for cycle reheat and the supplementary heat penalty,
so the Department is proposing to adopt these provisions in this NOPR
(section 6 of AHRI 920-2020, as enumerated in section 2.2.1(c) of the
proposed Appendix B).
iii. Target Supply Air Dry-Bulb Temperature
As discussed, in the July 2017 ASHRAE TP RFI, DOE noted that ANSI/
AHRI 920-2015 includes a requirement of minimum supply air temperature
of 70.0 [deg]F for all Standard Rating Conditions and a maximum dew-
point temperature of 55.0 [deg]F for Standard Rating Conditions for
dehumidification. In that document, DOE further noted that ANSI/ASHRAE
198-2013 requires a supply air temperature of 75.2 [deg]F or as close
to this value as the controls will allow during testing. As part of the
July 2017 ASHRAE TP RFI, DOE requested comment on the difference in
target supply air temperature requirements between ANSI/AHRI 920-2015
and ANSI/ASHRAE 198-2013, and the appropriate supply air temperature
for use in the DOE test procedure for DDX-DOASes. 82 FR 34427, 34438
(July 25, 2017).
AHRI and Goodman commented that the minimum supply air temperature
should be 70 [deg]F. AHRI added that ANSI/ASHRAE 198-2013, which was
developed based on previous versions of AHRI 920 that required a supply
air temperature of 75 [deg]F, is being updated to reflect the new value
of 70 [deg]F. (AHRI, No. 11 at p. 17; Goodman, No. 14 at p. 2)
As discussed in the previous subsection, DOE proposes to
incorporate by reference the provisions in section 6.1.4 of AHRI 920-
2020, which specifies setting the supply air dry-bulb temperature to
within a range of 70-75 [deg]F for tests to determine dehumidification
metrics. For all dehumidification tests, 75 [deg]F represents the
maximum supply air dry-bulb temperature above which a supplementary
cooling penalty must be applied. As noted in section III.B.3.d.ii of
this NOPR, a supplementary heat penalty must be applied for ISCOP2
calculations when the minimum supply air dry-bulb temperature of 70
[deg]F cannot be met in heating mode.
iv. Target Supply Air Dew-Point Temperature
Note 5 to Table 2 and note 6 to Table 3 in ANSI/AHRI 920-2015 state
that the maximum dew point for Standard Rating Conditions A through D
shall be 55.0 [deg]F. The industry consensus standard does not specify
whether these conditions apply to the outdoor air, supply air, or
return air. DOE interprets these requirements to apply to the supply
air because the humidity levels for outdoor air and return air are
already specified in the same tables.
Furthermore, although ANSI/AHRI 920-2015 specifies a maximum dew
point temperature, the industry test standard does not include
requirements to ensure that the dew-point temperature is maintained at
the same level while testing at the different Standard Rating
Conditions specified in ANSI/AHRI 920-2015. Many DDX-DOASes are
equipped with modulating/variable capacity compressors, thereby
allowing control for a given supply air dew point temperature. Allowing
a lower dew point temperature for Standard Rating Conditions B, C, and
D specified in ANSI/AHRI 920-2015 could give a better MRE rating for
those test points, but the unit would use more energy to the extent it
provides unnecessary excess dehumidification if operated in that
manner. DOE also recognizes that the conditioned space latent cooling
requirements for Standard Rating Condition A specified in ANSI/AHRI
920-2015 represent the worst-case scenario, so there would be no need
to deliver a lower dew point (i.e., excess dehumidification) for
Standard Rating Conditions B, C, and D. AHRI 920-2020 revises the
supply air dew point requirements. Section 6.1.3 of AHRI 920-2020
requires that the average supply air dew point for Standard Rating
Condition B, C, and D must be within 0.3 [deg]F of the Standard Rating
Condition A dew point value.
Accordingly, in this NOPR, DOE proposes to adopt the relevant
provisions found in section 6.1.3 in AHRI 920-2020, which explicitly
state that the supply air dew point temperature shall be 55.0 [deg]F or
below for all Standard Rating Conditions A through D when operated at a
barometric pressure of 29.92 in Hg, and that the supply air dew point
temperature for Standard Rating Conditions B, C, and D must be within
0.3 [deg]F of the measured supply air dew point temperature for
Standard Rating Condition A, as noted above.
v. Units With Staged Capacity Control
During testing, DDX-DOAS units with modulating compressors may be
able to achieve supply air conditions within the proposed tolerances of
the target conditions for Standard Rating Conditions B, C, and D.
However, units with staged capacity will not likely be able to do this
because they control capacity in larger increments. DDX-DOAS units with
staged capacity or reheat control unable to maintain stable operation
at the proposed dry-bulb and dew-point temperature targets within
proposed tolerances would have to cycle between two stages (or cycle
between the compressor(s) being on and off) to deliver average
conditioning consistent with the target.
Neither ANSI/AHRI 920-2015 nor ANSI/ASHRAE 198-2013 have provisions
to address units that cycle. In response to the July 2017 ASHRAE TP
RFI, AHRI commented that the time average testing method suggested by
DOE in its initial review section 6.6 of ANSI/AHRI 920-2015 would
prevent credit for over-dehumidifying at Standard Rating Conditions B,
C, and D, but is excessively complex. Instead, AHRI recommended a
calculated adjustment that does not credit moisture removal in excess
of the Standard Rating Condition A design dew-point temperature. (AHRI,
No. 11 at p. 20)
This issue has now largely been addressed in AHRI 920-2020.
Specifically, section 6 of AHRI 920-2020 prescribes a method to address
DDX-DOASes with staged capacity control that is consistent with the
aforementioned method of DOE's initial review. It differs from DOE's
suggested method in that it applies the weighted averaging on the basis
of the supply air humidity ratio rather than the dew point, and that it
applies any applicable supplementary cooling or heat penalty to
operation at each particular stage rather than after determination of a
weighted average supply air dry-bulb

[[Page 36033]]

temperature. Given the development of defined test requirements and
equations addressing over-dehumidification, DOE initially concludes
that the method in AHRI 920-2020 is not excessively complex. AHRI 920-
2020 requires that when testing DDX-DOASes with staged capacity control
in a dehumidification test condition having a supply condition dew
point target (e.g., Conditions B, C, or D), if the dew point
temperature cannot be controlled within the specified test tolerances
for a given part-load condition, a weighted average of the results of
two tests that bracket the target dew point temperature will be used.
In this NOPR, DOE is proposing to adopt the provisions in section 6 of
AHRI 920-2020 for achieving the target supply air conditions for units
with staged capacity control.
Staging of compressor capacity may also affect operation in heating
mode. Section 6 of AHRI 920-2020 prescribes methods for determining COP
to account for cycling between compressor stages, or for operation when
the lowest-capacity compressor stage provides more capacity than
required to heat the supply air to 75 [deg]F. These methods are similar
to the AHRI 920-2020 method for addressing staged compressor capacity
for dehumidification. Accordingly, DOE proposes to adopt the provisions
in AHRI 920-2020 for staged capacity heat pump DDX-DOASes in heating
mode.
e. Water-Cooled and Water-Source Heat Pump DX-DOAS Equipment
i. Test Conditions for Multiple-Inlet Water Sources
As discussed in the July 2017 ASHRAE TP RFI, the inlet water
temperatures in ANSI/AHRI 920-2015 Table 2 for testing water-cooled
DDX-DOASes differ from the water-source heat pump inlet temperature
conditions specified in Table 3 for water-source heat pump DDX-DOASes
tested using the ``water source'' test conditions. DOE requested
comment on the need for different dehumidification test conditions for
a water-cooled DDX-DOAS as compared to a water-source heat pump DDX-
DOAS using the closed water loop test conditions. 82 FR 34427, 34438
(July 25, 2017). In the July 2017 ASHRAE TP RFI, DOE also pointed out
that Tables 2 and 3 in ANSI/AHRI 920-2015 include two application
configurations \23\ for water-cooled DDX-DOASes and three application
configurations for water-source heat pump DDX-DOASes. Id. DOE notes
that ASHRAE 90.1-2016 established different standards for each of these
five application configurations.
---------------------------------------------------------------------------

\23\ In the context of ANSI/AHRI 920-2015, an application
configuration specifies test conditions based on the expected
application of the DDX-DOAS.
---------------------------------------------------------------------------

In response to the July 2017 ASHRAE TP RFI on this issue, AHRI
commented that the two sets of water temperatures for water-cooled DDX-
DOASes and water-source heat pump DDX-DOASes should be identical and
that the differences would be resolved in an update to ANSI/AHRI 920-
2015. (AHRI, No. 11 at p. 17) AHRI also commented that in almost all
cases, a single design is used for water-cooled equipment used with
cooling tower water and chilled water, and, similarly, a single design
is used for all of the water-source applications, adding that for each
of these cases, a single set of water conditions can be used for
testing. AHRI recommended that the various entering water and inlet
fluid conditions remain as presented in the ANSI/AHRI 920-2015
standard, but any regulated products are to be tested to the ``Chilled
Water Entering Condenser Temperature'' column values in Table 2 and the
``Water Source Heat Pumps'' column values in Table 3. (AHRI, No. 11 at
p. 17)
In response, DOE notes that AHRI 920-2020 still provides separate
inlet fluid rating conditions for the different water-cooled and water-
source heat pump DDX-DOAS applications but now identifies some as
optional application rating conditions. In light of the retention of
these separate inlet fluid rating conditions in AHRI 920-2020, DOE
surmises that AHRI's and industry's original position on these
conditions, as set forth in the comments in response to the July 2017
ASHRAE TP RFI, changed during the course of developing that industry
consensus standard. Table 4 of AHRI 920-2020 continues to include
separate inlet fluid rating conditions for water-cooled cooling tower
and water-cooled chilled water DDX-DOASes, but Note 3 to Table 4 of
AHRI 920-2020 indicates that the water-cooled chilled water condition
is the optional application rating condition, contrary to AHRI's
recommendation in response to the July 2017 ASHRAE TP RFI. Table 5 of
AHRI 920-2020 includes separate inlet fluid rating conditions for
water-source and ground-source closed-loop heat pump DDX-DOASes but
identifies the ground-source closed-loop conditions as the optional
application rating condition. Tables 4 and 5 of AHRI 920-2020 also
revise the inlet temperatures of the rating conditions for water-cooled
cooling tower, water-source heat pump, and water-source ground-source
closed-loop heat pump DDX-DOASes. In this NOPR, DOE is proposing to
adopt the water/fluid rating conditions provided in AHRI 920-2020
(section 6 of AHRI 920-2020, which includes Table 4 and Table 5, as
enumerated in section 2.2.1(c) and 2.2.2 of the proposed Appendix B),
including the chilled water and ground-source closed-loop conditions
specified as optional in AHRI 920-2020 so as to allow for voluntary
representations for those applications. In any future energy
conservation standards rulemaking for DDX-DOASes, DOE would consider
establishing standards and the corresponding certification requirements
in the context of the inlet fluid temperature conditions specific for
water-cooled cooling towers and for water-source heat pumps provided in
Table 4 and Table 5 of AHRI 920-2020, respectively.
ii. Condenser Liquid Flow Rate
In the July 2017 ASHRAE TP RFI, DOE noted that ANSI/AHRI 920-2015
provides instructions for setting the condenser liquid flow rate in
section 6.1.4 and condenser liquid entering temperature in Tables 2 and
3 when conducting the dehumidification test for water-cooled and water-
source heat pump DDX-DOASes. 82 FR 34427, 34437 (July 25, 2017).
Section 6.1.4 of ANSI/AHRI 920-2015 indicates to use the liquid flow
rates ``specified by the manufacturer.'' The manufacturer must specify
a single liquid flow rate for tests at all Standard Rating Conditions
as defined in ANSI/AHRI 920-2015, unless the unit is equipped with
automatic control of the liquid flow rate.
In the July 2017 ASHRAE TP RFI, DOE noted that ANSI/AHRI 340/360-
2007 and ANSI/AHRI 210/240-2008, which are incorporated by reference as
DOE's test procedures for rating water-cooled commercial air-
conditioning equipment, specify inlet and outlet water temperature
requirements rather than relying on manufacturers to determine water
flow rate. Further, both of these industry consensus standards specify
that the full-load water flow rate determined for the Standard Rating
Conditions should also be used for part-load rating conditions. DOE
further stated in the July 2017 ASHRAE TP RFI that these test methods
reflect the typical design temperature differential for cooling towers
serving water-cooled equipment, and they are very common for control of
condenser water pumps; hence, it is not clear to DOE why the same test
method would not be adopted for water-cooled DDX-DOAS. 82 FR 34427,
34437 (July 25 2017). As part of the July 2017 ASHRAE TP RFI, DOE
requested information on how

[[Page 36034]]

condenser water flow rates are set in the field, how they are
controlled at part-load, and whether the relevant provisions in ANSI/
AHRI 920-2015 provide sufficient guidance regarding how to set up water
flow for DDX-DOASes with automatic water flow control systems. Id.
AHRI and Carrier commented that the condenser water flow rates
should be set by the manufacturer or the installation instructions,
consistent with ANSI/AHRI 920-2015. (AHRI, No. 11 at p. 15; Carrier,
No. 6 at p. 5) Carrier added that for part-load conditions, setting the
condenser water flow rate will depend on what is needed for head
pressure control, and that this should be defined in the installation
instructions and followed for the test. Carrier stated that some
equipment may require no control and that others may use head pressure
flow regulating valves. (Carrier, No. 6 at p. 5) AHRI argued that any
variation in flow rate that occurs automatically based on the operation
and the equipment design will be measured during testing, with the
pressure drop at that flow rate also being measured. AHRI indicated
that the pumping penalty accounts for different manufacturer
specifications of flow rates and pressure drop at each of the test
conditions. (AHRI, No. 11 at p. 15)
As part of its update to the industry consensus test standard for
DDX-DOASes, AHRI added additional requirements for liquid flow rate.
More specifically, while section 6.1.6.1 of AHRI 920-2020 continues to
provide that the water flow rate be specified by the manufacturer, the
test method now adds that it must deliver a liquid temperature rise no
less than 8 [deg]F when testing under Standard Rating Condition A.
Section 6.1.6.2 of AHRI 920-2020 requires that the flow rate set under
Standard Rating Condition A be used for testing at the remaining
Standard Rating Conditions (B through F), unless automatic adjustment
of the liquid flow rate is provided by the equipment. Section 6.1.6.2
of AHRI 920-2020 also requires that if condenser water flow rate is
modulated under part-load conditions, the flow rate must not exceed the
flow rate set for Condition A.
DOE has tentatively concluded that the addition of a minimum
temperature differential in AHRI 920-2020 better reflects control
strategies for cooling towers serving water-cooled equipment and for
condenser water pumps while still leaving flexibility for manufacturers
to specify full-load flow rate and to implement options for modulating
flow rate at part-load conditions. The Department notes that the
provision allowing for automatic adjustment of the liquid flow rate for
part-load tests accounts for manufacturer control strategies, such as
condenser head pressure control, and is also accounted for in the water
pump effect (discussed in the following section). DOE has tentatively
concluded that these provisions would be representative of flow rates
during an average use cycle and would not be unduly burdensome to
conduct. Therefore, DOE is proposing to adopt the liquid flow
requirements in AHRI 920-2020 for water-cooled and water-source heat
pump DDX-DOASes (section 6 of AHRI 920-2020, which includes section
6.1.6 Liquid Flow Rates for Water-Cooled, Water-Source Heat Pump, and
Ground-Source Heat Pump), as enumerated in section 2.2.1(c) of the
proposed Appendix B.
iii. Water Pump Effect
As part of the July 2017 ASHRAE TP RFI, DOE noted that ANSI/AHRI
920-2015 includes an equation for calculating the ``water pump
effect,'' which is an estimate of the energy consumption of non-
integral water pumps (i.e., pumps that are not part of the DDX-DOAS
unit and whose power consumption would, therefore, not already be part
of the measured power). 82 FR 34427, 34438 (July 25 2017). DOE noted
that section 6.1.3 of ANSI/AHRI 920-2015 implies that this calculation
applies solely to water pumps serving refrigerant-to-liquid heat
recovery devices--no indication is given whether the equation also
applies for pumps serving water-source or water-cooled condensers--
although it is possible that the term ``refrigerant-to-liquid heat
recovery device'' refers to the condenser of a water-source heat pump
DDX-DOAS. Id.
In the July 2017 ASHRAE TP RFI, DOE requested confirmation that the
``refrigerant-to-liquid heat recovery device'' cited in section 6.1.3
of ANSI/AHRI 920-2015 is intended to include heat exchangers used for
heat rejection during the dehumidification cycle, and comment on
whether Equation 1 of this section for estimating the energy use of
water pumps is appropriate for DDX-DOASes with water-cooled condensers.
Id. In its comments, AHRI confirmed that the term ``refrigerant-to-
liquid heat recovery device'' is intended to include liquid-to-
refrigerant heat exchangers used in the dehumidification cycle and
heating cycle. (AHRI, No. 11 at p. 16)
The revisions to the industry consensus testing standard in AHRI
920-2020 clarify this matter and are consistent with the public
comments received. Section 6.1.6.4 of AHRI 920-2020 provides the water
pump effect equation, and section 11.1 of AHRI 920-2020 states within
the definition of symbol P<INF>E,x</INF> that the water pump effect
applies to all water-cooled and water-source units without integral
water pumps. Thus, DOE is proposing to adopt the water pump effect
provisions in sections 6.1.6.4 and 11.1 of AHRI 920-2020 to account for
the energy use of water pumps for water-cooled condensers, as
enumerated in section 2.2.1(c) and section 2.2.1(d) of the proposed
Appendix B, which reference sections 6 and 11 of AHRI 920-2020,
respectively.
In further clarification, the total pump effect does not need to be
calculated for pumps that are integral to the DDX-DOAS, because the
power for these pumps would be measured as part of the main DDX-DOAS
power measurement. Currently, the number of DDX-DOAS models on the
market with integral pumps is very limited. However, AHRI 920-2020 does
not explicitly state the amount of external head pressure \24\ to use
when testing DDX-DOASes with integral pumps, a necessary parameter. DOE
notes that the calculation of the water pump effect for DDX-DOASes
without integral pumps specified AHRI 920-2020 includes a fixed adder
of 25 Watts per gallon per minute based on 20 feet of water column of
external head pressure, a value which the Department reasons could be
suitably applied to DDX-DOASes with integral pumps. Accordingly, DOE is
proposing to include additional specifications in section 2.2.1(c)(ii)
of proposed Appendix B that DDX-DOASes with integral pumps be
configured with an external head pressure equal to 20 feet of water
column (i.e., the same level of external head pressure used in the
calculation of the pump effect for DDX-DOASes without integral pumps).
---------------------------------------------------------------------------

\24\ ``External head pressure'' reflects the pump power output,
in that it represents the height to which the pump can raise the
water if the water were being moved opposite the force of gravity.
---------------------------------------------------------------------------

DOE has initially determined that the proposal to specify the same
external head pressure for integral pumps as the external head pressure
used in the calculation of the pump effect for DDX-DOASes without
integral pumps is consistent with the industry consensus test
procedure. The proposed requirement would provide additional direction
for treatment of integral pumps consistent with the treatment of non-
integral pumps and would provide for the representative comparability
of results between DDX-DOASes with and without integral pumps. To the
extent the industry test procedure does not specify an external head
pressure for DDX-DOASes with an integral pump,

[[Page 36035]]

the industry test procedure would not ensure that measured results are
comparative, and due to the potential variation resulting from the
absence of the specification, the industry test procedure would not
ensure that the results reflect the equipment's representative average
energy efficiency or energy use. As such, DOE has initially determined,
supported by clear and convincing evidence, that in the absence of a
specification for the external head pressure for an integrated pump,
the industry test procedure would not meet the statutory requirements
of 42 U.S.C. 6314(a)(2)-(3) and is, therefore, proposing the
supplemental specification.
In addition, DOE is proposing a condition tolerance of up to 1 foot
of water column greater than the 20-foot requirement (which equates to
5 percent), which is equivalent to the condition tolerance on air side
external static pressure in Table 9 of AHRI 920-2020 (Test Operating
and Test Condition Tolerances); namely, the provision in that table
provides for up to 0.05 inch of water column greater than the target
external static pressure, which is around 1 inch of water column.
Similarly, DOE is proposing an operating tolerance of up to 1 foot of
water column, which is equivalent to the operating tolerance on air
side external static pressure in Table 9 of AHRI 920-2020; namely, the
provision in that table provides for 0.05 inch of water column. To the
extent the industry test procedure does not specify a condition
tolerance and operating tolerance for the water column, the industry
test procedure would not ensure consistent and comparable results and
would not ensure that the results reflect the equipment's
representative average energy efficiency or energy use. As such, DOE
has initially determined, supported by clear and convincing evidence,
in the that absence of such tolerances for the water column, the
industry test procedure would not meet the statutory requirements of 42
U.S.C. 6314(a)(2)-(3) and is, therefore, proposing the supplemental
specification.
Issue-6: DOE requests comment on the proposal to require that
water-cooled and water-source DDX-DOASes with integral pumps be set up
with an external pressure rise equal to 20 feet of water column with a
condition tolerance of -0/+1 foot and an operating tolerance of 1 foot.
iv. Energy Consumption of Heat Rejection Fans and Chillers
Neither ANSI/AHRI 920-2015 nor ANSI/ASHRAE 198-2013 address
accounting for the energy consumption of heat rejection fans (e.g.,
cooling tower fans) for water loops serving the condensers of water-
cooled DDX-DOASes. 82 FR 34427, 34438 (July 25, 2017). DOE noted that
section 6.1 of AHRI 340/360-2007, which is used for rating certain
water-cooled commercial package air conditioning and heat pump
equipment, provides a power consumption adjustment for both the cooling
tower fan and the circulating water pump (it is assumed that the pump
is external to the air conditioning equipment). Id. In addition,
neither ANSI/AHRI 920-2015 nor ANSI/ASHRAE 198-2013 address accounting
for the energy consumption of chiller systems used to provide chilled
water to DDX-DOASes with chilled-water-cooled condensers. In the July
2017 ASHRAE TP RFI, DOE requested comment on accounting for the energy
consumption for heat-rejection fans and chiller systems employed in
water-cooled or water-loop DDX-DOASes. Id.
AHRI commented that the AHRI test standard for certain commercial
package air conditioning and heat pump equipment includes the cooling
tower fan and pump energy as part of a flat rate adjustment, but that
the International Organization for Standardization (ISO) test standard
for water-source heat pumps does not account for cooling tower fan
energy use at this time. AHRI stated that the minimum efficiency values
for DDX-DOASes specified in ASHRAE 90.1-2016 were based on the current
ANSI/AHRI 920-2015 standard that does not account for the energy
consumption of heat-rejection fans or the chiller system, although it
does account for the additional water pumping energy (see the
discussion of the water pump effect in section III.B.3.e.iii of this
document). AHRI stated that, as a result, DOE should not account for
this energy in the efficiency metric for DDX-DOASes because doing so
introduces unknown impacts on the design and costs associated with
meeting the minimum efficiency requirements. (AHRI, No. 11 at pp. 16-
17) Carrier also commented that heat-rejection fans are not part of a
water-cooled unit but are part of the cooling tower rating and are
covered by Table 6.8.1.7 in ASHRAE 90.1-2016. (Carrier, No. 6 at p. 5)
Carrier commented that chiller system energy use should not be included
in the efficiency metric because this is not a system rating and is
only a component rating method for the DDX-DOAS itself. (Carrier, No. 6
at p. 6)
The revised AHRI 920-2020 also does not include energy use of the
heat-rejection fans and chiller systems employed in water-cooled or
water-loop DDX-DOASes. DOE observes that accounting for this energy use
is not a consistent industry practice, as evidenced by the differences
between the AHRI 340/360-2007 approach for more typical commercial
package air conditioning equipment and the ISO approach for water-
source heat pumps. The heat rejection fan addition for more typical
water-cooled commercial package air conditioning equipment is a modest
energy adder (around 10 percent of unit power).\25\ Furthermore,
including the energy of the heat rejection fan and chiller systems
would not help to distinguish between models of different efficiency,
since the adder would be identical for two same-capacity models with
different efficiencies. For these reasons, and consistent with AHRI
920-2020, DOE is not proposing in this NOPR to include any energy
consumption associated with heat rejection fans, cooling towers, or
chiller systems used to cool the water loops of water-cooled or water-
source DDX-DOASes.
---------------------------------------------------------------------------

\25\ For example, for a minimally-compliant 120,000 Btu/h water-
cooled unit with gas heat having a 12.5 EER (see 10 CFR 431.97 Table
1), the total electricity use is 120,000 Btu/h / 11.9 Btu/Wh =
10,084 W, and the heat rejection fan adder is 120,000 Btu/h x (10 W
per 1,000 Btu/h) = 1,200 W.
---------------------------------------------------------------------------

v. Chilled Water Coil Exclusion
In the July 2017 ASHRAE TP RFI, DOE noted that section 2 of ANSI/
ASHRAE 198-2013 specifically excludes equipment with water coils that
are supplied by a chiller located outside of the unit. 82 FR 34427,
34438 (July 25 2017). However, Table 2 in ANSI/AHRI 920-2015 includes
operating conditions for which a water-cooled condenser is supplied
with chilled water, and ASHRAE 90.1-2016 established standard levels
for DDX-DOASes that operate with chilled water as the condenser cooling
fluid. As part of the July 2017 ASHRAE TP RFI, DOE requested
confirmation that the ANSI/ASHRAE 198-2013 chiller exclusion applies to
cooling coils rather than condenser coils. Id.
In response to the July 2017 ASHRAE TP RFI, AHRI commented that
both ANSI/AHRI 920-2015 and ANSI/ASHRAE 198-2013 were designed for
units that contain vapor compression cycle-based cooling and
dehumidification with direct expansion coils. AHRI stated that direct
application of chilled water coils to cool and dehumidify is outside
the scope of the standard, as the energy for cooling is expended at an
external source of chilled water. (AHRI, No. 11 at p. 18) Carrier
commented that chillers should

[[Page 36036]]

only be used for cooling coils and not for condenser heat rejection
unless there is heat reclaim, and that this should be addressed through
a building efficiency standard such as ASHRAE 90.1. (Carrier, No. 6 at
p. 7)
AHRI 920-2020 did not make a change to the exclusion of DOASes with
water coils that are supplied by a chiller located outside of the unit;
AHRI's comment explains that the exclusion exists because chilled water
coil units that use the chilled water for cooling are not DX units, and
the industry test procedures are only for DOASes with DX cooling.
ASHRAE Standard 90.1 does not include standards for non-DX DOASes such
as those with chilled water coils used for cooling. Based on AHRI 920-
2020, and ANSI/ASHRAE 198-2013 as referenced, and the comments
received, DOE did not consider DOAS units that use chilled water coils
directly for cooling and dehumidifying. However, the comments provided
in response to the July 2017 ASHRAE TP RFI, as discussed in section
III.B.3.e.i of this document, indicate that DX-DOASes and DDX-DOASes
may still use chilled water for condenser coils. (AHRI, No. 11 at p.
17)
f. Defrost Energy Use for Air-Source Heat Pump
In the July 2017 ASHRAE TP RFI, DOE noted that tests conducted at
35 [deg]F dry-bulb temperature for consumer central air conditioning
heat pumps (which are air-source) consider the impacts of defrosting of
the outdoor coil in the energy use measurement (see section 3.9 of 10
CFR part 430, subpart B, appendix M), while defrost is not addressed in
ANSI/ASHRAE 198-2013. 82 FR 34427, 34436 (July 25 2017). DOE stated
that defrost has a real impact on efficiency because of energy use
associated with defrost and because a system cannot continue to provide
heating during defrost operation, thereby reducing time-averaged
capacity. Id. Hence, DOE noted that consideration of defrost could
provide a more field-representative measurement of performance. DOE
requested comment on whether testing for test condition E of ANSI/AHRI
920-2015 Table 2 (i.e., 35 [deg]F dry-bulb/29 [deg]F wet-bulb) should
consider energy use associated with defrost. Id.
On this issue, AHRI commented that, due to the constant volume
nature of the airflow in DDX-DOASes, the addition of defrost to DDX-
DOASes presents challenges, and it is not in a position to present a
proper solution at this time. AHRI also stated that it is aware of
manufacturers that disable the heat pump operation in cold temperatures
to avoid this issue. (AHRI, No. 11 at p. 13) The Joint Advocates,
Goodman, and Carrier commented that defrost should be accounted for in
the test procedure to provide a more representative measurement of
field energy use. (Joint Advocates, No. 9 at p. 4; Goodman, No. 14 at
p. 2; Carrier, No. 6 at p. 4) Carrier added that DOE should use the T-
test \26\ defined in ANSI/AHRI 340/360 and ANSI/AHRI 210/240. (Carrier,
No. 6 at p. 4) Goodman indicated that it will be very difficult to
precisely capture defrost in the DDX-DOASes test procedure. (Goodman,
No. 14 at p. 2)
---------------------------------------------------------------------------

\26\ The T-test is a non-steady-state (transient) test that
includes measurement of both the heating energy use as the outdoor
coil accumulates frost and the defrost energy use as the unit
undergoes multiple defrost cycles, as referenced in section 8.8.3 of
ANSI/ASHRAE 37-2009.
---------------------------------------------------------------------------

DOE understands that AHRI is referring to challenges in field
operation defrosting for air-source heat pump DDX-DOASes. Preventing
cold outdoor air from being brought into the supply air stream during a
defrosting sequence (when the DDX-DOAS cannot operate as a heat pump)
would require interruptions to the supply airflow, which is
inconsistent with building code requirements to provide a continuous
supply of ventilation air for most DDX-DOAS applications. DOE is aware
of only a limited number of air-source heat pump DDX-DOAS units. DOE
understands that these units may not continue heat pump operation
during potential frosting conditions as a result of these challenges in
field operation. Given these factors, DOE is not aware of test data
(e.g., from T-tests) for such heat pumps during extended heating mode
operation to understand better the level of frost accumulation and
associated defrost energy expenditure. DOE also notes that AHRI 920-
2020 does not include any provisions for testing or calculating the
defrost energy of DDX-DOAS air-source heat pumps. However, AHRI 920-
2020 arguably addresses this issue in another fashion, namely by
providing in section 5.5 that defrost control settings specified by the
manufacturer in installation instructions may be set prior to heating
mode tests in order to achieve steady-state conditions during the
heating mode tests. As discussed in section III.B.3.d of this document,
DOE is proposing to adopt the provisions of AHRI 920-2020 section 5.5,
Defrost Controls for Air-Source Heat Pump during Heating Mode, as
enumerated in section 2.2.1(b) of the proposed Appendix B. If these
settings fail to prevent frost accumulation during the heating mode
tests (resulting in unsteady conditions), then the manufacturer would
need to seek a waiver from the test procedure to obtain an alternate
method of test from DOE pursuant to 10 CFR 431.401. However, section
5.5 of AHRI 920-2020 also specifies that the Standard Rating Condition
F heating mode test (which represents low temperature environmental
conditions where frosting is likely) is optional to conduct, and if the
Standard Rating Condition F test is not conducted, a default COP of 1.0
(corresponding to electric resistance heating) is assigned at this
rating point instead. Therefore, the manufacturer may choose to not
conduct a test at Standard Rating Condition F instead of seeking a
waiver. DOE has tentatively concluded that the test method set forth in
section 5.5 of AHRI 920-2020 for defrost controls for air-source heat
pump DDX-DOASes during heating mode offers a reasonable and workable
approach, so the Department proposes to adopt such approach into the
Federal test procedure.
Due to the lack of sufficient information on how air-source heat
pump DDX-DOAS units operate under frosting conditions, DOE is not
proposing to include any provisions for including the defrost energy of
DDX-DOAS air-source heat pumps.
g. General Control Setting Requirements
Requirements for adjustment of unit controls during set-up for
testing of a DDX-DOAS are addressed in specific sections of AHRI 920-
2020. Some examples include the following. Section 5.2, ``Equipment
Installation,'' requires that units be installed per manufacturer's
installation instructions (MII). Section 5.4.3, ``Deactivation of
VERS,'' indicates that operation of the VERS may be deactivated for
Standard Rating Conditions C or D if the VERS is capable of being
deactivated. Section 5.5, ``Defrost Controls for Air-Source Heat Pump
during Heating Mode,'' provides instructions for setting of defrost
controls.
However, DOE notes that the test standard provides no general
requirements indicating whether control settings can be adjusted as the
test transitions through the four Standard Rating Conditions used for
testing. Manual readjustment of control settings would not generally
occur in field operation of DDX-DOASes as outdoor air conditions change
(i.e., in the field, controls are configured at the time of
installation and would not be actively adjusted on an ongoing basis in
response to changes in outdoor temperature or humidity). Hence, to
further ensure the representativeness of the test procedure, DOE is
proposing

[[Page 36037]]

inclusion of a general requirement that control settings remain fixed
and that there be no further manual adjustment thereof, once set
initially for the first of the Standard Rating Conditions (Standard
Rating Condition A). Absent such instruction, the controls could be
adjusted as the test transitions through the four Standard Rating
Conditions used for testing, which as discussed, would not be
representative of the operation of the unit in the field. As such, DOE
has initially determined, supported by clear and convincing evidence,
that absent instruction for the control settings to be fixed during
testing, the industry test procedure would not meet the statutory
requirements of 42 U.S.C. 6314(a)(2)-(3) and is, therefore, proposing
such instruction.
Notwithstanding this proposal, DOE recognizes that some manual
intervention, as permitted by AHRI 920-2020, and as specified in
supplemental test instructions (STI),\27\ may be necessary as the test
transitions through Standard Rating Conditions. However, such manual
interventions are only permitted in limited and specific instances as
identified in the test standard or STI. An example of such an allowed
intervention is the use of the manual setting of compressor capacity
staging for tests using the ``Weighted average method,'' as described
in section 6.9.1 of AHRI 920-2020. In field operation, a DDX-DOAS set
per the manufacturer's installation instructions would attempt to
achieve the target supply air dew point over the average of a time
period with cycling (unsteady) operation between two compressor stages;
to address this, the test standard calls for manual intervention, using
two steady-state tests, one using each stage, and calculating a
weighted average of the results. (This provision is discussed in depth
in section III.B.3.d.v of this NOPR.)
---------------------------------------------------------------------------

\27\ ``STI'' is defined in AHRI 920-2020 as additional
instructions provide by the manufacturer and certified to the U.S.
DOE. As explained in section III.C.1 of this document, this NOPR
does not propose certification requirements for DDX-DOAS--such
requirements will instead be proposed in a separate Energy
Conservation Standard rulemaking. Consistent with certification
provisions for other commercial packaged air-conditioning and
heating equipment, manufacturers include STI as part of the
certification (see 10 CFR 429.43(b)(4)). DOE is proposing that
manufacturers must adhere to the provisions of this test procedure
starting on the compliance date for the related energy conservation
standard rulemaking. Hence, this approach does not require that STI
exist earlier than the date it must be certified to DOE.
---------------------------------------------------------------------------

Thus, DOE is proposing to require that all control settings are to
remain unchanged for all Standard Rating Conditions once system set-up
has been completed, and component operation shall be controlled by the
unit under test once the provisions in section 6 of AHRI 920-2020
(Rating Requirements) are met, except as specifically allowed by the
test standard or STI (see section 2.2.1(b)(i) of the proposed Appendix
B).
Issue-7: DOE requests comment on the proposed general control
setting requirement for DDX-DOASes.
h. Ventilation Energy Recovery Systems
As discussed in section III.A.1 of this NOPR, the industry
definition of ``DX-Dedicated Outdoor Air System Units'' is inclusive of
units that provide pre-conditioning of outdoor air by direct or
indirect transfer with return/exhaust air using an enthalpy wheel,
sensible wheel, desiccant wheel, plate heat exchanger, heat pipes, or
other heat or mass transfer apparatus. These pre-conditioning features
are broadly referred to as ventilation energy recovery systems
(``VERS'', or ``energy recovery''). ASHRAE Standard 90.1-2016 defines
separate equipment classes and efficiency levels for DDX-DOASes with
VERS.
Section 5.4 of AHRI 920-2020 specifies testing requirements for
DDX-DOASes equipped with VERS. Section 5.4.1 of AHRI 920-2020 specifies
that units equipped with VERS can be tested using either one of two
options: ``Option 1'' or ``Option 2''. Option 1 requires operating the
DDX-DOAS unit with VERS as it would operate in the field, maintaining
the appropriate return air and outdoor air conditions for airflows
entering the unit, and operating the VERS to provide energy recovery
during the test (see section 5.4.1.1 of AHRI 920-2020).\28\ In addition
to specifying the outdoor air dry-bulb temperature and humidity
conditions, Table 4 and Table 5 of AHRI 920-2020 specify return air
inlet conditions that are applicable to DDX-DOASes with VERS. Section
C2.4 in Appendix C of AHRI 920-2020 also specifies that the return air
be ducted into the unit from a separate test room maintaining the
required return air inlet conditions.
---------------------------------------------------------------------------

\28\ The Option 1 test method includes additional specificity to
the test room configuration for testing DDX-DOAS with energy
recovery by allowing use of the three-chamber approach in addition
to the example configuration provided in the current industry
consensus test standard, in which the outdoor room is conditioned to
both the required outdoor dry-bulb and humidity conditions.
---------------------------------------------------------------------------

Option 2 involves setting the conditions of the air entering the
unit so as to simulate the conditions that would be provided by the
VERS in operation (see section 5.4.1.2 of AHRI 920-2020). Option 2 uses
energy recovery device performance ratings based on ANSI/AHRI 1060-2018
to calculate the air dry-bulb temperature and humidity conditions that
would be provided by the energy recovery device. ANSI/AHRI 1060-2018
references ANSI/ASHRAE 84-2013, ``Method of Testing Air-to-Air Heat/
Energy Exchangers,'' (ANSI/ASHRAE 84-2013) (approved by ASHRAE on
January 26, 2013) for conducting the test. These industry test
standards provide a method for rating the performance of VERS in terms
of sensible and latent effectiveness. DOE also notes that the
performance ratings for energy recovery devices certified using ANSI/
AHRI 1060-2018 are listed in AHRI's directory of certified product
performance.\29\
---------------------------------------------------------------------------

\29\ AHRI's directory of certified product performance for air-
to-air energy recovery ventilators can be found at
<a href="http://www.ahridirectory.org/ahridirectory/pages/erv/defaultSearch.aspx">www.ahridirectory.org/ahridirectory/pages/erv/defaultSearch.aspx</a>.
---------------------------------------------------------------------------

The operating conditions specified in ANSI/AHRI 1060-2018 may be
different than the operating conditions specified for testing DDX-DOAS
(i.e., airflow rate, which subsequently affects factors such as
transfer/leakage airflow \30\). Hence, section C4 of AHRI 920-2020
provides methods to adjust, for the DDX-DOAS operating conditions, the
effectiveness values for sensible and latent transfer measured using
ANSI/AHRI 1060-2018. Section C4 of AHRI 920-2020 also provides default
values for sensible effectiveness and latent effectiveness. These can
be used in cases where performance rating information based on ANSI/
AHRI 1060-2018 is not available for a VERS, or the rotational speed for
an energy recovery wheel has been changed from the speed used to
determine performance ratings using ANSI/AHRI 1060-2018.
---------------------------------------------------------------------------

\30\ As discussed in section III.B.4.g.i of this NOPR, DDX-
DOASes with energy recovery wheel VERS may experience air transfer
and leakage from the outdoor air path to the exhaust air (outdoor
air transfer and leakage) and return air to the supply air (return
air transfer and leakage).
---------------------------------------------------------------------------

The Option 2 approach would reduce test burden for most test
laboratories by reducing the number of test rooms required as compared
to conducting tests using Option 1. Because the outdoor ventilation air
and return air would be maintained at the same conditions, there would
be no transfer of heat or moisture in the VERS, nor any change of VERS-
outlet supply air conditions associated with transfer or leakage of
return air to the supply air plenum. In addition, testing using Option
2 is conducted with all components operating (e.g., with an energy
recovery wheel rotating, or with the pump of a glycol-water runaround
loop activated), such that all measurements would be representative

[[Page 36038]]

of the pressure drops and power consumption associated with the VERS.
This approach avoids separate testing to measure power input of
auxiliary components or of the exhaust air fan.
Option 2 is applicable for DDX-DOASes for which a VERS provides the
initial outdoor ventilation air treatment. DDX-DOAS units with VERS
that provide conditioning downstream of the conditioning coil could not
be tested using Option 2, since this option addresses VERS pre-
conditioning only upstream of the conditioning coil. Such units would
need to be tested using Option 1.
In response to the July 2017 ASHRAE TP RFI, AHRI commented that
testing of DDX-DOAS units with VERS would generally require a facility
with three adjacent test chambers, which is not available in the known
stock of existing laboratory spaces. (AHRI, No. 11 at p. 14) AHRI
stated that the test facility arrangement for testing of DDX-DOASes
with energy recovery presented in ANSI/ASHRAE 198-2013,\31\ as
referenced by AHRI 920-2020, is not adequate because laboratories
cannot maintain both the required dry-bulb temperature and high
humidity conditions in the outdoor room, since removing the high
condenser heat load using a conventional conditioning system also
excessively dehumidifies the chamber. The commenter also argued that
capacity and stratification are significant issues with the existing
test arrangement. AHRI surmised that a separate, third test room to
provide conditioned outdoor air for the entering air to the energy
recovery device would be required to provide adequate stability for
testing. AHRI further asserted that because it is not feasible to
adequately test units with VERS, DOE should limit the scope of the
Federal test procedure at this time to DDX-DOAS units without VERS.
(AHRI, No. 11 at p. 15)
---------------------------------------------------------------------------

\31\ See section 6.1.1.2 and Figure 2 of ANSI/ASHRAE 198-2013.
---------------------------------------------------------------------------

Based on DOE's review of the test requirements and equipment
available on the market, DOE is aware of test facilities capable of
testing using Option 1 for smaller DDX-DOAS units. Test facilities with
similar configurations used for testing variable refrigerant flow
multi-split air-conditioning and heat pump equipment would be large
enough and equipped with enough controlled test rooms to meet the DDX-
DOAS test procedure requirements. DDX-DOAS units with physical
dimensions under 10 feet by 10 feet (typically less than 100 lbs. per
hour MRC at Standard Rating Condition A), which represent more than 50
percent of equipment models available on the market, could be tested in
these existing test facilities.
Option 2 allows existing test facilities to test all DDX-DOAS
units, including units larger than those that can be tested using
Option 1. As discussed, Option 2 requires neither a separate third test
room to condition the outdoor ventilation air to the required
temperature and humidity conditions, nor that the outdoor room in which
the unit is located be conditioned to both the required dry-bulb and
humidity conditions, because it does not require use of an air stream
at outdoor air conditions. Aside from the chamber in which the test
unit is installed, it requires only a second chamber at the simulated
conditions. The inclusion of Option 2 in AHRI 920-2020 reduces testing
burden compared to the ANSI/AHRI 920-2015, which only provides test
set-up and provisions that are mostly equivalent to the Option 1 method
in AHRI 920-2020 discussed previously. For these reasons, DOE
tentatively concludes that existing test facilities would be capable of
using the proposed test procedure for testing DDX-DOASes both with and
without VERS.
DOE is required under EPCA to adopt a Federal test procedure that
is consistent with the applicable test procedure specified in the
amended ASHRAE Standard 90.1 unless DOE determines, supported by clear
and convincing evidence, that to do so would result in a test procedure
that is not designed to produce test results which reflect the energy
efficiency of DDX-DOASes in a representative average-use cycle or would
be unduly burdensome to conduct. (42 U.S.C. 6314(a)(4)(B); 42 U.S.C.
6314(a)(2) and (3)) In this NOPR, DOE is proposing to adopt the two
options (i.e., Option 1 and Option 2) for testing DDX-DOASes with
energy recovery, as provided in section 5.4.1 of AHRI 920-2020 (as
enumerated in section 2.2.1(b) of the proposed Appendix B). As
discussed further in section III.B.3.a of this NOPR, DOE is proposing
to define a ``ventilation energy recovery system'' as a feature that
provides pre-conditioning of outdoor ventilation air entering the
equipment through direct or indirect thermal and/or moisture exchange
with the exhaust air leaving the unit.
In addition, DOE notes that the relevant industry test standards
(AHRI 920-2020 and ASHRAE 198-2013) in some cases use synonymous but
different terms to denote VERS. DOE proposes to include a section
2.3(b) in its proposed Appendix B indicating that the different
synonymous terms all refer to VERS as defined in 10 CFR 431.92.
The following subsections address specific aspects of the proposed
test procedure pertaining to DDX-DOASes with VERS.
i. Exhaust Air Transfer and Leakage
DOE is aware that DDX-DOASes with energy recovery wheel VERS may
experience air transfer and leakage from the outdoor air path to the
exhaust air (outdoor air transfer and leakage) and return air to the
supply air (return air transfer and leakage). Some of this air is
leakage past the diametral seals that separate the outdoor and exhaust
plenums on one side of the wheel and the return and supply plenums on
the other side. Additional leakage from outdoor to exhaust or return to
supply could be due to loose cabinet construction of the DDX-DOAS
itself. Depending on the geometry of the energy recovery wheel media
(e.g., whether the sheets of media making up the energy recovery wheel
core are oriented parallel to this leakage flow direction), the air may
pass through a portion of the media near the diametral seal. In
addition, as a portion of the wheel passes from one side of the seal to
the other, the air within that portion reverses direction--this
represents either return air transferred to the supply side or outdoor
air transferred to the exhaust side. The exhaust air transfer ratio
(EATR) is defined in section 3.8 of AHRI 920-2020 as the fraction of
airflow leaving the VERS that transfers or leaks from the return air
inlet rather than passing through the VERS from the outdoor air inlet.
The return air that transfers and leaks to the supply air side of
an energy recovery wheel did not enter the DDX-DOAS as outdoor
ventilation air. Therefore, the amount of fresh outdoor air delivered
by the DDX-DOAS is less than the supply airflow and is equal to the
supply airflow multiplied by the factor (1-EATR). In addition, the
return air is already at neutral space conditions. Hence, the energy
recovery wheel does not provide any meaningful conditioning for this
air. When calculating MRC for a DDX-DOAS with an energy recovery wheel,
section 10.5 of ANSI/ASHRAE 198-2013 indicates that the calculation is
based on the full supply airflow. DOE notes that any transfer or
leakage air would increase the apparent dehumidification provided by
the DDX-DOAS unit, since this air is already at space-neutral
conditions--thus, a high EATR would boost the efficiency rating without
providing any real benefit (for VERS other than energy recovery wheels,
the EATR is considered to be equal to 0, under the assumption that
cabinet air leakage

[[Page 36039]]

through the VERS is negligible, so this issue would not affect these
other VERS). ANSI/AHRI 920-2015 includes tracer gas tests for measuring
EATR in its standard rating requirements (see section 5.1). As part of
the July 2017 ASHRAE TP RFI, DOE raised this issue, while recognizing
that such leakage may be low enough in most energy recovery wheels that
the EATR measurement could represent an unnecessary addition to test
burden. 82 FR 34427, 34437 (July 25 2017). DOE requested comment on
whether EATR should be included in the test procedure for DDX-DOASes
and, if so, how it should be used in determining DX-DOAS ratings. Id.
In response to the RFI, on this issue, AHRI commented that the
intent of the DOE test procedure for DDX-DOASes should not be to
quantify energy recovery performance. AHRI pointed out that the AHRI
certification directory publishes EATR values based on AHRI 1060.
(AHRI, No. 11 at p. 15) In addition, AHRI argued that test laboratories
of sufficient size for testing DDX-DOASes are not currently equipped
with tracer gas test equipment, as specified in ANSI/ASHRAE 84-2013.
(AHRI, No. 11 at p. 14) No other comments were received on this issue.
Since the July 2017 ASHRAE TP RFI, further refinements were made to
the industry consensus test standard which have bearing on this matter.
Specifically, sections 6 and C4 of AHRI 920-2020 were revised to
include methods to estimate EATR without requiring a tracer gas
measurement, and to account for EATR's impact on DDX-DOAS performance,
using calculations tailored for testing under either Option 1 or Option
2. These include using an EATR value that is based on testing in
accordance with ANSI/AHRI 1060-2018 with zero purge angle,\32\ zero
return-to-supply pressure differential, and 100-percent of nominal
energy recovery wheel supply airflow, and adjusting the EATR value for
the DDX-DOAS supply airflow rate based on an assumption that the
leakage/transfer flow is not affected by the supply and return air flow
rates. The adjusted value of EATR is then used in the calculation of
DDX-DOAS performance. Specifically, the MRC calculations in section 6.9
of AHRI 920-2020 take into account the conditioning of the air that
leaked or transferred from the return plenum to the supply plenum
(equal to adjusted EATR multiplied by supply airflow) only from return
conditions to supply conditions to reflect the fact that this air did
not enter the DDX-DOAS unit at outdoor air conditions. In cases where
EATR rating information based on ANSI/AHRI 1060-2018 is not available,
or if, for an energy recovery wheel, the rotational speed has been
changed from the speed used to determine performance ratings using
ANSI/AHRI 1060-2018, sections 6.5 and C4 of AHRI 920-2020 provide a
default value of EATR that would be used to rate the DDX-DOAS.
---------------------------------------------------------------------------

\32\ A purge mechanism cleans the portion of the wheel that has
had contact with return air before it is used to precondition
outdoor air. The cleaning is provided by outdoor air that passes
through this portion of the wheel and is diverted into the return
plenum to be discharged through the exhaust blower. Most purge
mechanisms allow adjustment of the angle of the wheel sector that is
subject to this cleaning function. At zero purge angle, there is no
purge cleaning provided.
---------------------------------------------------------------------------

DOE has tentatively determined that the use of default or certified
values for EATR in AHRI 920-2020 (instead of tracer gas tests) has
addressed AHRI's comments on quantifying energy recovery performance.
Accordingly, DOE is proposing to adopt these changes made by AHRI 920-
2020 (section 6.5 Determination of EATR), as enumerated in section
2.2.1(c) of the proposed Appendix B; and Appendix C of AHRI 920-2020
(which includes section C4 Simulated Ventilation Air Conditions for
Testing Under Option 2), as enumerated in section 2.2.1(f) of the
proposed Appendix B).
ii. Purge Angle Setting
Section 6.6 of ANSI/ASHRAE 198-2013 requires that for any DDX-DOAS
equipped with an energy recovery wheel, the purge angle of such feature
must be set to zero when testing the DDX-DOAS unit. As part of the July
2017 ASHRAE TP RFI, DOE requested comment on whether all purge devices
are adjustable to zero purge and whether it is always clear how to set
them to zero purge. 82 FR 34427, 34439 (July 25, 2017). DOE also
requested comment on whether it is appropriate to set purge to zero or
whether it would be more appropriate to set purge to its highest
setting or to some other standard setting. Id.
None of the comments on the RFI indicated that there are purge
devices that are not adjustable to zero angle, nor that it is unclear
how to adjust purge angle to zero. Carrier commented that for the short
period of time required for a performance test, it should not be a
problem to set the purge angle to zero. (Carrier, No. 6 at p. 8) As
discussed previously, AHRI stated that there are no independent
laboratories capable of testing DDX-DOAS units with VERS. As a result,
AHRI argued that this issue does not need to be addressed at this time.
However, AHRI stated, if in the future laboratories are able to test
DDX-DOASes equipped with VERS, then manufacturers should be allowed to
specify the purge setting for testing, as is done in AHRI 1060. (AHRI,
No. 11 at p. 20)
DOE has tentatively concluded that a zero purge angle aligns with
the selection that manufacturers would generally make (i.e., a zero
purge angle), because non-zero purge prevents the purge portion of the
wheel from contributing to energy recovery effectiveness (since outdoor
ventilation air passing through it is ejected out of the unit to the
exhaust rather than becoming part of the supply airflow). Also, the
purge section restricts the flow area for the remaining outdoor air
that becomes supply air, thus increasing pressure drop and fan power.
For these reasons, energy recovery wheel performance (and likewise DDX-
DOAS performance and efficiency) will be reduced when operating with a
non-zero purge angle. Furthermore, basing DDX-DOAS performance ratings
on a zero purge angle provides greater consistency in testing. DOE
notes that section C4.1 of AHRI 920-2020--the industry consensus test
standard--includes a requirement for testing DDX-DOAS units using zero
purge angle, whether testing using Option 1 or Option 2 (through
inclusion of EATR<INF>0</INF>, which is defined in section 11 of AHRI
920-2020 as being determined using zero purge angle). For these
reasons, DOE is proposing to adopt the requirement in AHRI 920-2020 to
use a zero purge angle for testing DDX-DOAS with energy recovery wheels
(section C4.1 of Appendix C of AHRI 920-2020), as enumerated in section
2.2.1(f) of the proposed Appendix B.
iii. Return Air External Static Pressure Requirements
ANSI/ASHRAE 198-2013 specifies testing DDX-DOASes with VERS with
return air passing into the unit and exiting at the exhaust air
connection. DOE noted in the July 2017 ASHRAE TP RFI that ANSI/AHRI
920-2015 does not address setting the external static pressure (ESP)
for the return airflow. 82 FR 34427, 34437 (July 25, 2017). DDX-DOAS
units are typically installed and operated in the field with return air
ducting. Therefore, when in operation, the return air fans consume
additional energy to overcome the static pressure imposed by the return
air ducts. As part of the July 2017 ASHRAE TP RFI, DOE requested
comment on the ESP levels that should be used for return airflow. Id.
In response, AHRI stated that Table 4 of ANSI/AHRI 920-2015 was
intended to represent ESP of both supply and return airflow. AHRI also
stated that

[[Page 36040]]

revisions to ANSI/AHRI 920-2015 will refer to the same table for return
airflow ESP. (AHRI, No. 11 at p. 15) DOE received no other comments on
this issue.
Consistent with the AHRI comment, section 6.1.5.6 of AHRI 920-2020
does include different ESP requirements for supply and return airflow,
thereby resolving the identified issue. Accordingly, DOE is proposing
to adopt the ESP requirements set forth in AHRI 920-2020 (section 6.1.5
Supply and Return Airflow Rates), as enumerated in section 2.2.1(c) of
the proposed Appendix B).
iv. Target Return Airflow Rate
In the July 2017 ASHRAE TP RFI, DOE noted that for testing DDX-DOAS
units equipped with VERS, Tables 2 and 3 in ANSI/AHRI 920-2015 provide
return airflow temperature conditions and indicate that the temperature
conditions apply to units with energy recovery at balanced airflow. 82
FR 34427, 34437 (July 25, 2017). It is unclear from ANSI/AHRI 920-2015
what airflow streams should be balanced, how to determine if they are
balanced, and within what tolerances they should be balanced. In the
July 2017 ASHRAE TP RFI, DOE requested comments on which airflow
streams should be balanced and whether balanced airflow is
representative of field use. Id.
On this topic, AHRI raised a number of issues with testing DDX-DOAS
equipped with VERS generally, as previously discussed. AHRI also stated
that using balanced airflows is consistent with the test procedure for
rating VERS described in ANSI/AHRI 1060-2018. AHRI further commented
that in field operation, unbalanced flows may be needed to maintain
positive building pressure; however, most equipment selection is done
at or near balanced airflows. (AHRI, No. 11 at pp. 14-15)
Subsequent updates to the industry consensus test standard at AHRI
920-2020 shed further light on this issue. Specifically, section 6.1.5
of AHRI 920-2020 specifies the return airflow rate must be within 3
percent of the measured supply airflow rate. Based on DOE's review of
DDX-DOAS product literature and consideration of the AHRI comment, it
has become apparent that there is no clear optimal ratio of supply
airflow to return airflow for DDX-DOAS testing to be representative of
field use. Therefore, DOE has tentatively concluded that the provision
in AHRI 920-2020 is appropriate.
i. Demand-Controlled Ventilation
DDX-DOAS units are often used in demand-controlled ventilation
(DCV) operation, which regulates the building ventilation requirement
based on parameters such as building occupancy. Typically, a DCV system
monitors the concentration of carbon dioxide (CO<INF>2</INF>) in the
return air or in the building and regulates the supply airflow rate
accordingly. During periods of non-occupancy, which could represent a
significant portion of field-use, the DCV system controls the unit to
operate at a low airflow rate, thereby reducing the unit's overall
energy use. DDX-DOASes using DCV systems are typically equipped with
variable-speed supply fans that can be adjusted to meet changing
ventilation needs. In the July 2017 ASHRAE TP RFI, DOE sought comments
on whether to include operation under DCV conditions (i.e., low supply
airflow conditions) to be included as part of DOE's test procedure. 82
FR 34427, 34437 (July 25, 2017).
In response to this issue, the Joint Advocates encouraged DOE to
adopt an efficiency metric that captures the benefits of DCV. The Joint
Advocates stated that adopting such a metric could provide more field-
representative equipment ratings and better inform consumers when
purchasing equipment. Further, the Joint Advocates argued that
capturing the benefits of DCV would promote adoption of variable speed
fans, provide more flexibility in building operation, and reduce energy
use. (Joint Advocates, No. 9 at p. 2, 4) AHRI and Carrier commented
that the performance of the DX-DOAS under DCV operation must be
characterized prior to developing a test procedure and that adopting
provisions to address DCV operation could significantly increase the
cost and complexity of testing. AHRI further stated that DCV operation
is primarily controlled by building operators. Carrier stated that
performance would depend highly on the building type, occupancy, and
site requirements for demand ventilation. (AHRI, No. 11 at p. 14;
Carrier, No. 6 at p. 4)
DOE reviewed the comments and considered whether to adopt testing
conditions to account for the energy use profiles of models with low
supply airflow rates that are typically experienced by units with DCV.
Incorporation of the airflow modulation that would be enabled by DCV
might provide more representative efficiency ratings, help in consumer
decision making, and potentially promote the market penetration of
variable speed fans. However, DOE is not aware of representative field
data regarding the typical DDX-DOAS duty cycle when operating with DCV
and, thus, agrees with the comments of AHRI and Carrier that
characterization of DCV performance would be an important first step in
integrating this control feature into the test procedure. DOE further
agrees that adopting additional testing requirements to capture the
effect of DCV could significantly increase testing cost and complexity,
as noted in comments provided by AHRI and Carrier. Given the lack of
data on in-field performance and the anticipated additional testing
burden of such a test, DOE has tentatively decided not to include
performance under DCV operation in its proposed test procedure for DDX-
DOASes at this time.
j. Tolerances for Supply and Return Airflow and External Static
Pressure
DOE noted in the July 2017 ASHRAE TP RFI that Table 1 of ANSI/
ASHRAE 198-2013 includes operating and condition tolerances of 5
percent for airflow rate. 82 FR 34427, 34439 (July 25, 2017). It
includes a test operating tolerance for ESP equal to 0.05 in
H<INF>2</INF>O and a test condition tolerance for ESP of 0.02 in
H<INF>2</INF>O. As provided in section 5.2.2 of ANSI/AHRI 920-2015, the
airflow rate and ESPs are set at Standard Rating Condition C dry-bulb
temperatures without the refrigeration systems and energy recovery (if
applicable) in operation. ANSI/AHRI 920-2015 states in section 5.2.2.4
that once the airflow rate is set, the fan speeds shall not be adjusted
for the remaining tests. DDX-DOAS units that are for use with air
ducting are required by the industry test standard to be set up with
ESP requirements in Table 4 of ANSI/AHRI 920-2015, and units tested as
if they would be installed without ducts are tested with 0 in
H<INF>2</INF>O ESP.
DOE notes that while operating in dehumidification mode, the
airflow rates and ESPs may fluctuate more than for ``dry'' operation as
condensate accumulates and then drains from the cooling coil. In
addition, for dehumidification and heating tests, the density of supply
air may be different, which may change fan performance, and, thus, the
ESP. These factors could cause the supply air ESP to fluctuate more
than the operating tolerances specified in Table 1 of ANSI/ASHRAE 198-
2013, and/or to deviate from the specified ESP by more than the test
condition tolerance. Likewise, the airflow rates could fluctuate more
than the specified operating tolerances, and the average airflows could
deviate by more than the test condition tolerances

[[Page 36041]]

from their target values. If this occurs, it is not clear how
manufacturers would correct the issue without being able to adjust the
fan speed and ESP, since such action is precluded by section 5.2.2.4 of
ANSI/AHRI 920-2015.
In the July 2017 ASHRAE TP RFI, DOE noted that the 5-percent
condition tolerance on airflow rate is less stringent than the 3-
percent condition tolerance adopted in DOE's test procedure for more
typical commercial package air equipment. 82 FR 344271, 34439 (July 25,
2017). On August 6, 2015, DOE published a test procedure NOPR that
proposed to apply a <plus-minus>5-percent condition tolerance on
cooling full-load indoor airflow rate for more typical commercial
package air conditioning equipment. 80 FR 46870, 46873. In response to
the proposed tolerance for more typical commercial package air
conditioning equipment, DOE received several comments suggesting that a
5-percent tolerance would result in too much variation in the
measurement of energy efficiency ratio and cooling capacity. After
considering stakeholder comments, DOE adopted a 3-percent tolerance in
a final rule published on December 23, 2015. 80 FR 79655, 79659-79660.
As part of the July 2017 ASHRAE TP RFI, DOE expressed concern that that
the 5-percent condition tolerance on airflow in ANSI/ASHRAE 198-2013
may result in too much test variability for DDX-DOASes and requested
comment on whether this airflow tolerance is acceptable. 82 FR 34427,
34439 (July 25, 2017).
AHRI commented in response to the July 2017 ASHRAE TP RFI that
manufacturers who have performed testing have stated that meeting the
tolerances specified in ANSI/AHRI 920-2015 and ASHRAE 198-2013 is not
feasible due to how the testing is performed. Once the refrigeration
system is engaged for determining ISMRE and ISCOP ratings, changes in
moisture present on the cooling coil and air density affect the
standard airflow and associated ESP. AHRI recommended that the <plus-
minus>0.05 in H<INF>2</INF>O ESP tolerance and a 3-percent airflow
tolerance be observed during the airflow and fan speed setting at
Standard Rating Condition C without the refrigeration system operating.
AHRI also stated that during the Standard Rating Condition tests, the
DDX-DOAS fan speeds and airflow-measuring apparatus fan speeds shall
not be adjusted, consistent with airflow setting and operation in the
field. Nevertheless, AHRI stated that the average measured airflows
should be required to be within 5 percent of the manufacturer's rated
standard airflow during all rating tests and that the average measured
ESPs should be within 15 percent of the required ESP to indicate a
valid test, but the commenter did not indicate whether the fans of the
test unit or the airflow-measuring apparatus should be adjusted to
maintain these tolerances. (AHRI, No. 11 at p. 18)
DOE notes that AHRI 920-2020 revised the test condition and
operating tolerances for airflow and ESP. Section 6.1.5 of AHRI 920-
2020 specifies airflow test condition tolerances of <plus-minus>3
percent of the manufacturer-provided airflow rate for all DDX-DOASes
when setting the airflow, provided that this airflow rate meets the
supply air dew point temperature requirement, as discussed in section
III.B.4.d.i of this NOPR. For setting the return airflow rate, section
6.1.5 of AHRI 920-2020 specifies the same test condition tolerances as
for supply airflow rate, except that for return airflow rate, the
target is equal to the measured supply airflow rate. This specification
ensures that supply and return airflows remain balanced, as discussed
in section III.B.3.h.iv of this NOPR. These test condition tolerances
for airflow and ESP are only required when setting the airflow. Once
the airflow rate is set, the dehumidification and heating tests are
then conducted without further adjustments to the supply fan, return
fan, or airflow measuring apparatus. Section 6.1.5 and Table 9 of AHRI
920-2020 indicate that the supply and return airflow and ESP condition
tolerances are not required to be maintained during the
dehumidification and heating tests. While these provisions are contrary
to AHRI's recommendation in response to the July 2017 ASHRAE TP RFI to
impose a 5-percent airflow condition tolerance and a 15-percent ESP
condition tolerance during dehumidification and heating tests, DOE
believes these changes in AHRI 920-2020 address AHRI's concerns about
testing problems associated with the tolerances in ANSI/AHRI 920-2015
and ASHRAE 198-2013.
AHRI 920-2020 additionally includes a list of test operating
tolerances, including those for external static pressure and airflow
nozzle differential pressure. AHRI 920-2020 does not include changes to
the test operating tolerance for ESP (0.05 in H2O total observed range,
specified in Table 9 of AHRI 920-2020). Whereas ANSI/ASHRAE 198-2013
provides a 5-percent operating tolerance directly on the airflow rate,
Table 9 of AHRI 920-2020 provides a 5-percent operating tolerance for
airflow rate in the form of airflow nozzle differential pressure. DOE
has initially determined that the airflow operating tolerance approach
in AHRI 920-2020 is preferable because the airflow nozzle differential
pressure provides a more direct indication of the airflow variation,
since airflow is calculated based on this value. Additionally, other
industry test standards such as ANSI/ASHRAE 37-2009 include an
operating tolerance on the nozzle pressure drop rather than directly on
airflow. DOE believes that these operating tolerances, in addition to
the condition tolerances for setting airflow, would maintain repeatable
and reproducible results while ensuring that testing is representative
of field use. Accordingly, DOE is proposing to adopt the test condition
and operating tolerances for airflow and ESP specified in AHRI 920-2020
(section 6.1.5 Supply and Return Airflow Rates and section 6.6.2 Test
Measurement Tolerances, which contains Table 9), as enumerated in
section 2.2.1(c) of the proposed Appendix B).
k. Secondary Dehumidification and Heating Capacity Tests
Commercial package air-conditioners and heat pumps with cooling
capacity less than 135,000 Btu/h are required to undergo a secondary
test to verify the cooling or heating capacity and energy efficiency
results (see, e.g., ANSI/ASHRAE 37-2009 section 7.2.1, which is
referenced by appendix A to subpart F of 10 CFR part 431). Neither
ANSI/AHRI 920-2015 nor ANSI/ASHRAE 198-2013 specify a secondary test
method for verifying the dehumidification and heating capacity of DDX-
DOAS, but section 6.7 of AHRI 920-2020 does specify secondary tests.
The measurement of dehumidification and heating performance of DDX-
DOASes is based on measurements of airflow rate, temperature, and
humidity, which have uncertainties associated with them. Thus, a
secondary test method may be essential to confirm the accuracy of the
primary test method.
As part of the July 2017 ASHRAE TP RFI, DOE requested comment on
the need for a secondary test method requirement for DDX-DOAS testing.
82 FR 34427, 34439 (July 25, 2017). AHRI commented that condensate
measurement would be appropriate as a secondary method, if energy
recovery units are excluded from the test procedure. (AHRI, No. 11 at
p. 19)
Section C5.1 of AHRI 920-2020 includes a condensate-based test
method as a secondary measure of dehumidification capacity. The method
measures the weight of the condensate (i.e., water vapor in the outdoor
ventilation air that condenses on the conditioning coil and is removed
from

[[Page 36042]]

the air) collected during the dehumidification test and uses it to
calculate a secondary measure of MRC. This secondary measure of MRC is
then compared to the primary MRC measurement, which is based on supply
and outdoor ventilation airflow and air condition measurements.
AHRI 920-2020 requires this secondary measure of MRC for all
dehumidification tests, and comparison to the primary measure of MRC at
Standard Rating Condition A. This requirement is for all DDX-DOAS units
that: (a) Do not use condensate collected from the dehumidification
coil to enhance condenser cooling or include a secondary
dehumidification process for which the moisture removed from the supply
air stream is not collectable in liquid form, and (b) either are not
equipped with VERS or are equipped with VERS and tested using Option 2
(see section C5.1 of AHRI 920-2020). AHRI 920-2020 does not require a
secondary dehumidification capacity measurement for DDX-DOAS units
equipped with VERS that are tested using Option 1. DOE understands that
this is because: (a) No viable method has been developed and validated
that appropriately accounts for the water vapor that transfers between
air streams of an energy recovery wheel, and (b) the test burden of
accounting for moisture in the exhaust air stream would be excessive.
DOE is proposing to adopt the secondary capacity test measurements
specified in AHRI 920-2020 (section C5.1 Dehumidification Capacity
Verification), as enumerated in section 2.2.1(f) of the proposed
Appendix B), including the cooling condensate secondary test
measurement discussed previously.
For DDX-DOAS units with energy recovery tested using Option 2, as
discussed in section III.B.3.h of this NOPR, the test is conducted by
setting the conditions of the air entering the unit (at both the
outdoor air inlet and return air inlet) to simulate the conditions that
would be provided by the energy recovery device in operation. As a
result, the moisture removal (in dehumidification mode) or heating (in
heating mode for heat pump DDX-DOAS) measured during the Option 2
primary and secondary capacity tests reflects only the moisture removed
or heating by the conditioning coil. The MRC or qhp for the DDX-DOAS is
calculated by adjusting the measured moisture removal or heating for
the primary test to account for the total moisture removal or heating
by the energy recovery device and the conditioning coil. Because the
moisture removal or heating capacity measured for the primary and
secondary tests are based on the simulated test conditions, sections
6.9 and 6.10 of AHRI 920-2020 use these measured values for the
secondary capacity verification under Option 2. DOE is proposing to
adopt these requirements specified in AHRI 920-2020 (section 6.9
Moisture Removal Efficiency Ratings and section 6.10 Heating Capacity),
as enumerated in section 2.2.1(c) of the proposed Appendix B).
a. Corrections
In addition to substantive changes, AHRI 920-2020 also provides
minor corrections to instructions in ANSI/AHRI 920-2015. However, in
its review of AHRI 920-2020, DOE identified an error and an omission in
the latest industry test procedure. Specifically, DOE notes that
section 6.9.2 of AHRI 920-2020 provides erroneous instruction for the
calculation of the degradation coefficient, and sections 6.1.5.2.3 and
6.1.5.2.4 of AHRI 920-2020 refer to the term ``non-standard low-static
motor'' without providing a definition or explanation of this term. DOE
proposes to correct the calculation instruction and define the term
``non-standard low-static motor,'' as discussed further in the
following paragraphs. DOE also notes a correction made by AHRI 920-2020
to address an error in the calculation of supplementary heat penalty in
ANSI/AHRI 920-2015.
i. Calculation of the Degradation Coefficient
As mentioned in section III.B.3.d.v of this NOPR, AHRI 920-2020
includes provisions for cases where the unit provides excess
dehumidification or heating capacity when operating at its lowest-
capacity compressor stage. A degradation coefficient is applied to the
MRE and MRE<INF>70</INF> when the supply air dew point temperature
measured when operating the unit at its lowest-capacity compressor
stage is lower than the target supply air dew point temperature in
excess of the specified test condition tolerance. This degradation
coefficient accounts for the re-evaporation of condensate which occurs
during cycling operation (i.e., when the compressor cycles on and off
to achieve the target supply air dew point temperature). DOE
understands that the degradation is more pronounced for DDX-DOASes
equipped with VERS for latent energy recovery (or total energy
recovery), and, thus, the degradation coefficient should be greater for
DDX-DOASes operating total energy recovery VERS. Equation 20 in section
6.9.2 of AHRI 920-2020 appears to incorrectly attribute the lower
degradation coefficient to DDX-DOASes operating with VERS. As such, DOE
has initially determined, supported by clear and convincing evidence,
that absent a correction, the degradation coefficient as applied in
AHRI 920-2020 would not meet the statutory requirements of 42 U.S.C.
6314(a)(2)-(3) because it would not produce representative results. DOE
proposes to correct Equation 20 by specifying that it is to be used for
DDX-DOASes ``without VERS, with deactivated VERS (see section 5.4.3 of
AHRI 920-2020), or with sensible-only VERS tested under Standard Rating
Conditions other than D'' (emphasis added) because DDX-DOASes with
total energy recovery VERS or with sensible-only VERS tested under
Standard Rating Condition D are considered separately in Equation 21,
which calculates a greater degradation coefficient. This correction
would be implemented in section 2.2.1(c)(iii) of proposed Appendix B.
ii. Non-Standard Low-Static Motor
As mentioned in section III.B.3.d.i of this NOPR, section 6.1.5 of
AHRI 920-2020 includes instructions for setting the supply airflow rate
for testing. In particular, sections 6.1.5.2.1 through 6.1.5.2.5 of
AHRI 920-2020 provide directions for adjusting the fans should an
initial attempt at setting the airflow be unsuccessful.
Section 6.1.5.2.3 of AHRI 920-2020 specifies that if a fan's
maximum speed is too low to satisfy the airflow and external static
pressure requirements within tolerance (i.e., the motor speed is at the
highest setting, a larger compatible off-the-shelf sheave is not
available, or increased speed would overload the motor or motor drive)
and the motor is not a ``non-standard low-static motor,'' the tests are
to be conducted at the fan's maximum speed with the external static
pressure satisfying the requirements in Table 7. However, if the motor
is a ``non-standard low-static motor,'' section 6.1.5.2.4 of AHRI 920-
2020 specifies that the maximum available speed should be used but the
supply and return airflow rates should satisfy aforementioned tolerance
requirements (implying that the external static pressure requirements
in Table 7 need not be met). AHRI 920-2020 does not define ``non-
standard low-static motor'' in order to determine which of the two
methods is appropriate. Without a definition of ``non-standard low-
static motor,'' manufacturers may not apply the ``maximum speed''
provisions consistently, and the potential for variation risks results
that do not reflect the equipment's representative average energy
efficiency or energy use. As

[[Page 36043]]

such, DOE has initially determined, supported by clear and convincing
evidence, that in the absence of a definition of ``non-standard low-
static motor,'' the industry test procedure would not meet the
statutory requirements of 42 U.S.C. 6314(a)(2)-(3).
DOE understands that a non-standard low-static fan motor may be
used for DDX-DOASes where the application requires less ductwork, which
results in a lower external static pressure when operating at the same
nominal supply or return airflow rate. This motor would be distributed
in commerce as part of an individual model within the same basic model
of DDX-DOAS that is also distributed in commerce with a motor that can
meet the external static pressure required by AHRI 920-2020. A parallel
situation occurs for Commercial and Industrial Unitary Air-conditioning
and Heat Pump Equipment, for which section D3 in Appendix D of AHRI
Test Standard 340/360-2019, ``Performance Rating of Commercial and
Industrial Unitary Air-conditioning and Heat Pump Equipment'' (AHRI
340/360-2019) defines ``non-standard motor'' as an indoor fan motor
that is not the standard indoor fan motor and that is distributed in
commerce as part of an individual model within the same Basic Model.
The same section D3 defines ``standard indoor fan motor'' as the motor
specified by the manufacturer for testing and shall be distributed in
commerce as part of a particular model. In both cases, the non-standard
motor has a horsepower level that is not compatible with the external
static pressure rating condition--for DDX-DOAS, the issue arises when
the non-standard motor does not have sufficient power to deliver the
required external static pressure. Therefore, in the proposed Appendix
B in section 2.2.1(a)(i), DOE is proposing to define ``non-standard
low-static fan motor'' as a supply fan motor that cannot maintain
external static pressure as high as specified in Table 7 of AHRI 920-
2020 when operating at a manufacturer-specified airflow rate and that
is distributed in commerce as part of an individual model within the
same basic model of a DDX-DOAS that is distributed in commerce with a
different motor specified for testing that can maintain the required
external static pressure.
Issue-8: DOE is requesting comment on the proposed definition of
``non-standard low-static fan motor'' and whether the proposed
definition reflects stakeholder understanding of the term.
iii. Calculation of Supplementary Heat Penalty
Section 6.1.3.1 of ANSI/AHRI 920-2015 includes a supplementary heat
penalty for units that are unable to achieve the minimum supply air
dry-bulb temperature of 70 [deg]F while testing at each Standard Rating
Condition specified in Table 2 and Table 3 of ANSI/AHRI 920-2015. The
supplementary heat penalty calculates the difference in enthalpy from
the delivered supply air and air at the minimum supply air temperature
(70 [deg]F). After reviewing the equations, DOE noted in the July 2017
ASHRAE TP RFI that the term for supply airflow rate is missing from the
supplementary heat penalty equations. 82 FR 34427, 34436 (July 25,
2017).
In response to the July 2017 ASHRAE TP RFI, AHRI confirmed that the
supplementary heat formula in ANSI/AHRI 920-2015 is missing the airflow
term, QSA, in section 6.1.3.1, and the organization committed to
include such term in the next revision of the test standard. (AHRI, No.
11 at p. 11) DOE notes that this change has been included in AHRI 920-
2020, thereby resolving the problem. Accordingly, DOE proposes to adopt
the revised supplementary heat penalty equation contained in AHRI 920-
2020 that includes the supply airflow rate term (section 6.1.3.1
Initial Standard Rating Condition A Dehumidification Test), as
enumerated in section 2.2.1(c) of the proposed Appendix B).
In the July 2017 ASHRAE TP RFI, DOE further noted that section
6.1.3.1 of ANSI/AHRI 920-2015 calls for a supplementary heat penalty if
the supply air temperature is less than 70 [deg]F, but the
incorporation of this penalty into the MRE and COP equations is not
clearly described. DOE also noted that it is not clear whether the
ANSI/ASHRAE 198-2013 test method considers this penalty. 82 FR 34427,
34436-34437 (July 25, 2017).
AHRI commented that the supplementary heat penalty should be added
if the minimum 70 [deg]F temperature is not met, and that this value is
added to the measured power input, which is represented as PT in
section 10.6 of ANSI/ASHRAE 198-2013. (AHRI, No. 11 at p. 11) DOE notes
that this clarification is included in section 6.9 of AHRI 920-2020 in
the calculation of MRE<INF>70</INF>, which incorporates the energy
impact of heating the supply air to 70 [deg]F. As discussed in section
III.B.2 of this NOPR, DOE is proposing to adopt the ISMRE2 metric
specified in section 6.13 of AHRI 920-2020 that does not include the
supplementary heat penalty as the regulated metric for DDX-DOAS, while
the MRE<INF>70</INF> (and ISMRE2<INF>70</INF>) metric that incorporates
the supplementary heat penalty may be used for representations. As a
result, the supplementary heat penalty would only be added to the total
power input for the calculation of the optional MRE<INF>70</INF>
ratings.
With regards to the COP calculation, AHRI commented that the intent
was that the supplementary heat penalty would be added to the numerator
as additional heat capacity and the denominator as additional power
consumed to calculate a COP indicative of running an electric heater to
meet a supply air temperature of 70 [deg]F. (AHRI, No. 11 at p. 13) DOE
notes that this clarification was included in section 6.11.2 of AHRI
920-2020 in the renamed COPISCOP metric, and accordingly, DOE is
proposing to adopt the revised COPISCOP calculation (section 6.11.2 of
AHRI 920-2020), as enumerated in section 2.2.1(c) of the proposed
Appendix B).
2. Determination of Represented Values
a. Basic Model
To determine the energy efficiency of a basic model, DOE's
certification requirements generally require manufacturers to test a
sample of units of that basic model to represent its performance. (10
CFR 429.11) The basic model may in

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