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Code of Federal Regulations (Last Updated: November 8, 2024) |
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Title 10 - Energy |
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Chapter II—Department of Energy |
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SubChapter D—Energy Conservation |
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Part 431 - Energy Efficiency Program for Certain Commercial and Industrial Equipment |
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Subpart R - Walk-in Coolers and Walk-in Freezers |
Appendix C1 to Subpart R of Part 431 - —Uniform Test Method for the Measurement of Net Capacity and AWEF2 of Walk-In Cooler and Walk-In Freezer Refrigeration Systems
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Appendix C1 to Subpart R of Part 431—Uniform Test Method for the Measurement of Net Capacity and AWEF2 of Walk-In Cooler and Walk-In Freezer Refrigeration Systems
Note:Prior to October 31, 2023, representations with respect to the energy use of refrigeration components of walk-in coolers and walk-in freezers, including compliance certifications, must be based on testing conducted in accordance with the applicable provisions for 10 CFR part 431, subpart R, appendix C, revised as of January 1, 2022. Beginning October 31, 2023, representations with respect to energy use of refrigeration components of walk-in coolers and walk-in freezers, including compliance certifications, must be based on testing conducted in accordance with appendix C to this subpart.
For any amended standards for walk-in coolers and walk-in freezers published after January 1, 2022, manufacturers must use the results of testing under this appendix to determine compliance. Representations related to energy consumption must be made in accordance with this appendix when determining compliance with the relevant standard. Manufacturers may also use this appendix to certify compliance with any amended standards prior to the applicable compliance date for those standards.
0. Incorporation by Reference
DOE incorporated by reference in § 431.303, the entire standard for AHRI 1250–2020, ANSI/ASHRAE 16, ANSI/ASHRAE 23.1–2010, ANSI/ASHRAE 37, ANSI/ASHRAE 41.1, ANSI/ASHRAE 41.3, ANSI/ASHRAE 41.6, and ANSI/ASHRAE 41.10. However, certain enumerated provisions of these standards, as set forth in sections 0.1 through 0.8 of this appendix are inapplicable. To the extent there is a conflict between the terms or provisions of a referenced industry standard and the CFR, the CFR provisions control. To the extent there is a conflict between the terms or provisions of AHRI 1250–2020, ANSI/ASHRAE 16, ANSI/ASHRAE 23.1–2010, ANSI/ASHRAE 37, ANSI/ASHRAE 41.1, ANSI/ASHRAE 41.3, ANSI/ASHRAE 41.6, and ANSI/ASHRAE 41.10, the AHRI 1250–2020 provisions control.
0.1 AHRI 1250–2020
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 9 Minimum Data Requirements for Published Rating, is inapplicable
(d) Section 10 Marking and Nameplate Data, is inapplicable
(e) Section 11 Conformance Conditions, is inapplicable
0.2 ANSI/ASHRAE 16
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
(d) Normative Appendices E–M, are inapplicable
(e) Informative Appendices N–R, are inapplicable
0.3 ANSI/ASHRAE 23.1–2010
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
0.4 ANSI/ASHRAE 37
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
(d) Informative Appendix A Classifications of Unitary Air-conditioners and Heat Pumps, is inapplicable.
0.5 ANSI/ASHRAE 41.1
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
(d) Section 9 Test Report, is inapplicable
(e) Informative Appendices A–C, are inapplicable
0.6 ANSI/ASHRAE 41.3
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
(d) Section 6 Instrument Types (informative), is inapplicable
(e) Section 8 Test Report, is inapplicable
(f) Informative Annexes A–D, are inapplicable
0.7 ANSI/ASHRAE 41.6
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
(d) Section 9 Test Report, is inapplicable
(e) Informative Appendices A–D, are inapplicable
0.8 ANSI/ASHRAE 41.10
(a) Section 1 Purpose, is inapplicable
(b) Section 2 Scope, is inapplicable
(c) Section 4 Classifications, is inapplicable
(d) Section 10 Test Report, is inapplicable
(e) Informative Annexes A–D, are inapplicable
1. Scope
This appendix covers the test requirements used to determine the net capacity and the AWEF2 of the refrigeration system of a walk-in cooler or walk-in freezer.
2. Definitions
2.1. Applicable Definitions
The definitions contained in § 431.302, AHRI 1250–2020, ANSI/ASHRAE 37, and ANSI/ASHRAE 16 apply to this appendix. When definitions in standards incorporated by reference are in conflict or when they conflict with this section, the hierarchy of precedence shall be in the following order: § 431.302, AHRI 1250–2020, and then either ANSI/ASHRAE 37 or ANSI/ASHRAE 16.
The term “unit cooler” used in AHRI 1250–2020 and this subpart shall be considered to address both “unit coolers” and “ducted fan coil units,” as appropriate.
2.2. Additional Definitions
2.2.1. Digital Compressor means a compressor that uses mechanical means for disengaging active compression on a cyclic basis to provide a reduced average refrigerant flow rate in response to a control system input signal.
2.2.2. Displacement Ratio, applicable to staged positive displacement compressor systems, means the swept volume rate, e.g. in cubic centimeters per second, of a given stage, divided by the swept volume rate at full capacity.
2.2.3. Duty Cycle, applicable to digital compressors, means the fraction of time that the compressor is engaged and actively compressing refrigerant.
2.2.4. Maximum Speed, applicable to variable-speed compressors, means the maximum speed at which the compressor will operate under the control of the dedicated condensing system control system for extended periods of time, i.e. not including short-duration boost-mode operation.
2.2.5. Minimum Speed, applicable to variable-speed compressors, means the minimum compressor speed at which the compressor will operate under the control of the dedicated condensing system control system.
2.2.6. Multiple-Capacity, applicable for describing a refrigeration system, indicates that it has three or more stages (levels) of capacity.
2.2.7. Speed Ratio, applicable to variable-speed compressors, means the ratio of operating speed to the maximum speed.
3. Test Methods, Measurements, and Calculations
Determine the Annual Walk-in Energy Factor (AWEF2) and net capacity of walk-in cooler and walk-in freezer refrigeration systems by conducting the test procedure set forth in AHRI 1250–2020, with the modifications to that test procedure provided in this section. However, certain sections of AHRI 1250–2020, ANSI/ASHRAE 37, and ANSI/ASHRAE 16 are not applicable, as set forth in sections 0.1, 0.2, and 0.3 of this appendix. Round AWEF2 measurements to the nearest 0.01 Btu/Wh. Round net capacity measurements as indicated in table 1 of this appendix.
Table 1—Rounding of Refrigeration System Net Capacity
Net capacity range, Btu/h Rounding
multiple,
Btu/h<20,000 100 ≥20,000 and <38,000 200 ≥38,000 and <65,000 500 ≥65,000 1,000 The following sections of this appendix provide additional instructions for testing. In cases where there is a conflict, the language of this appendix takes highest precedence, followed by AHRI 1250–2020, then ANSI/ASHRAE 37 or ANSI/ASHRAE 16. Any subsequent amendment to a referenced document by the standard-setting organization will not affect the test procedure in this appendix, unless and until the test procedure is amended by DOE. Material is incorporated as it exists on the date of the approval, and a notification of any change in the incorporation will be published in the Federal Register.
3.1. Instrumentation Accuracy and Test Tolerances
Use measuring instruments as described in section 4.1 of AHRI 1250–2020, with the following additional requirement.
3.1.1. Electrical Energy Input measured in Wh with a minimum accuracy of ±0.5% of reading (for Off-Cycle tests per footnote 5 of Table C3 in section C3.6.2 of AHRI 1250–2020).
3.2. Test Operating Conditions
Test conditions used to determine AWEF2 shall be as specified in Tables 4 through 17 of AHRI 1250–2020. Tables 7 and 11 of AHRI 1250–2020, labeled to apply to variable-speed outdoor matched-pair refrigeration systems, shall also be used for testing variable-capacity single-packaged outdoor refrigeration systems, and also for testing multiple-capacity matched-pair or single-packaged outdoor refrigeration systems. Test conditions used to determine AWEF2 for refrigeration systems not specifically identified in AHRI 1250–2020 are as enumerated in sections 3.5.1 through 3.5.6 of this appendix.
3.2.1 Test Operating Conditions for High-Temperature Refrigeration Systems
For fixed-capacity high-temperature matched-pair or single-packaged refrigeration systems with indoor condensing units, conduct tests using the test conditions specified in table 2 of this appendix. For fixed-capacity high-temperature matched-pair or single-packaged refrigeration systems with outdoor condensing units, conduct tests using the test conditions specified in table 3 of this appendix. For high-temperature unit coolers tested alone, conduct tests using the test conditions specified in table 4 of this appendix.
Table 2—Test Operating Conditions for Fixed-Capacity High-Temperature Indoor Matched Pair or Single-Packaged Refrigeration Systems
Test description Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering
relative
humidity, %1Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb,
°FCompressor
statusTest objective Off-Cycle Power 55 55 Compressor Off Measure total input wattage during compressor off-cycle, (Ėcu,off + ĖFcomp,off).2 Refrigeration Capacity A 55 55 90 3 75,4 65 Compressor On Determine Net Refrigeration Capacity of Unit Cooler, input power, and EER at Test Condition. Table 3—Test Operating Conditions for Fixed-Capacity High-Temperature Outdoor Matched-Pair or Single-Packaged Refrigeration Systems
Test
descriptionUnit cooler
air entering
dry-bulb,
°FUnit cooler
air entering
relative
humidity,
%1Condenser
air entering
dry-bulb,
°FCondenser
air entering
wet-bulb,
°FCompressor
statusTest objective Refrigeration Capacity A 55 55 95 3 75,4 68 Compressor On Determine Net Refrigeration Capacity of Unit Cooler, input power, and EER at Test Condition. Off-Cycle Power, Capacity A 55 55 95 3 75,4 68 Compressor Off Measure total input wattage during compressor off-cycle, ( Ėcu,off + ĖFcomp,off)2. Refrigeration Capacity B 55 55 59 3 54,4 46 Compressor On Determine Net Refrigeration Capacity of Unit Cooler and system input power at moderate condition. Off-Cycle Power, Capacity B 55 55 59 3 54,4 46 Compressor Off Measure total input wattage during compressor off-cycle, (Ėcu,off + ĖFcomp,off)2. Refrigeration Capacity C 55 55 35 3 34,4 29 Compressor On Determine Net Refrigeration Capacity of Unit Cooler and system input power at cold condition. Off-Cycle Power, Capacity C 55 55 35 3 34,4 29 Compressor Off Measure total input wattage during compressor off-cycle, (Ėcu,off + ĖFcomp,off)2. Table 4—Test Operating Conditions for High-Temperature Unit Coolers
Test description Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering
relative
humidity, %1Suction
dew point
temp, °F34Liquid inlet
bubble point
temperature,
°FLiquid inlet
subcooling,
°FCompressor
statusTest objective Off-Cycle 55 55 105 9 Compressor Off Measure unit cooler input wattage during compressor off-cycle, ĖFcomp,off.2 Refrigeration Capacity 55 55 38 105 9 Compressor On Determine Net Refrigeration Capacity of Unit Cooler, input power, and EER at Test Condition. 3.2.2 Test Operating Conditions for CO2 Unit Coolers
For medium-temperature CO2 Unit Coolers, conduct tests using the test conditions specified in table 5 of this appendix. For low-temperature CO2 Unit Coolers, conduct tests using the test conditions specified in table 6 of this appendix.
Table 5—Test Operating Conditions1 for Medium-Temperature CO2 Unit Coolers
Test title Unit cooler
air entering
dry-bulb,
°FUnit cooler
air entering
relative
humidity,
%Suction
dew point
temp,3
°FLiquid inlet
bubble point
temperature,
°FLiquid inlet
subcooling,
°FCompressor
operating modeTest objective Off-Cycle Power 35 <50 Compressor Off Measure unit cooler input wattage during compressor off-cycle, ĖFcomp,off2. Refrigeration Capacity, Ambient Condition A 35 <50 25 38 5 Compressor On Determine Net Refrigeration Capacity of Unit Cooler, q̇mix,rack Table 6—Test Operating Conditions for Low-Temperature CO2 Unit Coolers
Test title Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering
relative
humidity, %Suction
dew point
temp,2 °FLiquid inlet
bubble point
temperature,
°FLiquid inlet
subcooling, °FCompressor
operating modeTest objective Off-Cycle Power −10 <50 Compressor Off Measure unit cooler input wattage during compressor off-cycle, ĖFcomp,off.2 Refrigeration Capacity, Ambient Condition A −10 <50 −20 38 5 Compressor On Determine Net Refrigeration Capacity of Unit Cooler, q̇mix,rack. Defrost −10 <50 Compressor Off Test according to Appendix C Section C10 of AHRI 1250–2020, ḊF,Q̇DF. 3.2.3 Test Operating Conditions for Two-Capacity Condensing Units Tested Alone
For two-capacity medium-temperature outdoor condensing units tested alone, conduct tests using the test conditions specified in table 7 of this appendix. For two-capacity medium-temperature indoor condensing units tested alone, conduct tests using the test conditions specified in table 8 of this appendix. For two-capacity low-temperature outdoor condensing units tested alone, conduct tests using the test conditions specified in table 9 of this appendix. For two-capacity low-temperature indoor condensing units tested alone, conduct tests using the test conditions specified in table 10 of this appendix.
Table 7—Test Operating Conditions for Two-Capacity Medium-Temperature Outdoor Dedicated Condensing Units
Test description Suction
dew point, °FReturn gas, °F Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb, °F1Compressor status Capacity, Condition A, Low Capacity 24 41 95 75 Low Capacity, k=1. Capacity, Condition A, High Capacity 23 41 95 75 High Capacity, k=2. Off-Cycle, Condition A 95 75 Off. Capacity, Condition B, Low Capacity 24 41 59 54 Low Capacity, k=1. Capacity, Condition B, High Capacity 23 59 54 High Capacity, k=2. Off-Cycle, Condition B 59 54 Off. Capacity, Condition C, Low Capacity 24 41 35 34 Low Capacity, k=1. Capacity, Condition C, High Capacity 23 41 35 34 High Capacity, k=2. Off-Cycle, Condition C 35 34 Off. Table 8—Test Operating Conditions for Two-Capacity Medium-Temperature Indoor Dedicated Condensing Units
Test description Suction
dew point, °FReturn gas, °F Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb, °F1Compressor status Capacity, Condition A, Low Capacity 24 41 90 75 Low Capacity, k=1. Capacity, Condition A, High Capacity 23 41 90 75 High Capacity, k=2. Off-Cycle, Condition A 90 75 Off. Table 9—Test Operating Conditions for Two-Capacity Low-Temperature Outdoor Dedicated Condensing Units
Test title Suction
dew point,
°FReturn gas,
°FCondenser
air entering
dry-bulb,
°FCondenser
air entering
wet-bulb,
°F1Compressor operating mode Capacity, Condition A, Low Capacity −22 5 95 75 Low Capacity, k=1. Capacity, Condition A, High Capacity −22 5 95 75 High Capacity, k=2. Off-Cycle, Condition A 95 75 Compressor Off. Capacity, Condition B, Low Capacity −22 5 59 54 Low Capacity, k=1. Capacity, Condition B, High Capacity −22 5 59 54 High Capacity, k=2. Off-Cycle, Condition B 59 54 Compressor Off. Capacity, Condition C, Low Capacity −22 5 35 34 Low Capacity, k=1. Capacity, Condition C, High Capacity −22 5 35 34 High Capacity, k=2. Off-Cycle, Condition C 35 34 Compressor Off. Table 10—Test Operating Conditions for Two-Capacity Low-Temperature Indoor Dedicated Condensing Units
Test title Suction
dew point, °FReturn gas, °F Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb, °F1Compressor operating mode Capacity, Condition A, Low Capacity −22 5 90 75 Low Capacity, k=1. Capacity, Condition A, High Capacity −22 5 90 75 High Capacity, k=2. Off-Cycle, Condition A 90 75 Compressor Off. 3.2.4 Test Operating Conditions for Variable- or Multiple-Capacity Condensing Units Tested Alone
For variable-capacity or multiple-capacity outdoor medium-temperature condensing units tested alone, conduct tests using the test conditions specified in table 11 of this appendix. For variable-capacity or multiple-capacity indoor medium-temperature condensing units tested alone, conduct tests using the test conditions specified in table 12 of this appendix. For variable-capacity or multiple-capacity outdoor low-temperature condensing units tested alone, conduct tests using the test conditions specified in table 13 of this appendix. For variable-capacity or multiple-capacity indoor low-temperature condensing units tested alone, conduct tests using the test conditions specified in table 14 of this appendix.
Table 11—Test Operating Conditions for Variable- or Multiple-Capacity Medium-Temperature Outdoor Dedicated Condensing Units
Test description Suction
dew point, °FReturn gas, °F Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb, °F1Compressor status Capacity, Condition A, Minimum Capacity 24 41 95 75 Minimum Capacity, k=1. Capacity, Condition A, Intermediate Capacity 24 41 95 75 Intermediate Capacity, k=i. Capacity, Condition A, Maximum Capacity 23 41 95 75 Maximum Capacity, k=2 Off-Cycle, Condition A 95 75 Off. Capacity, Condition B, Minimum Capacity 24 41 59 54 Minimum Capacity, k=1. Capacity, Condition B, Intermediate Capacity 24 41 59 54 Intermediate Capacity, k=i. Capacity, Condition B, Maximum Capacity 23 41 59 54 Maximum Capacity, k=2. Off-Cycle, Condition B 59 54 Off. Capacity, Condition C, Minimum Capacity 24 41 35 34 Minimum Capacity, k=1. Capacity, Condition C, Intermediate Capacity 24 41 35 34 Intermediate Capacity, k=i. Capacity, Condition C, Maximum Capacity 23 41 35 34 Maximum Capacity, k=2. Off-Cycle, Condition C 35 34 Off. Table 12—Test Operating Conditions for Variable- or Multiple-Capacity Medium-Temperature Indoor Dedicated Condensing Units
Test description Suction
dew point, °FReturn gas, °F Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb, °F1Compressor status Capacity, Condition A, Minimum Capacity 24 41 90 75 Minimum Capacity, k=1. Capacity, Condition A, Intermediate Capacity 24 41 90 75 Intermediate Capacity, k=i. Capacity, Condition A, Maximum Capacity 23 41 90 75 Maximum Capacity, k=2. Off-Cycle, Condition A 90 75 Off. Table 13—Test Operating Conditions for Variable- or Multiple-Capacity Low-Temperature Outdoor Dedicated Condensing Units
Test title Suction
dew point,
°FReturn gas,
°FCondenser
air entering
dry-bulb,
°FCondenser
air entering
wet-bulb,
°F1Compressor operating mode Capacity, Condition A, Minimum Capacity −22 5 95 75 Minimum Capacity, k=1. Capacity, Condition A, Intermediate Capacity −22 5 95 75 Intermediate Capacity, k=i. Capacity, Condition A, Maximum Capacity −22 5 95 75 Maximum Capacity, k=2. Off-Cycle, Condition A 95 75 Compressor Off. Capacity, Condition B, Minimum Capacity −22 5 59 54 Minimum Capacity, k=1. Capacity, Condition B, Intermediate Capacity −22 5 59 54 Intermediate Capacity, k=i. Capacity, Condition B, Maximum Capacity −22 5 59 54 Maximum Capacity, k=2. Off-Cycle, Condition B 59 54 Compressor Off. Capacity, Condition C, Minimum Capacity −22 5 35 34 Minimum Capacity, k=1. Capacity, Condition C, Intermediate Capacity −22 5 35 34 Intermediate Capacity, k=i. Capacity, Condition C, Maximum Capacity −22 5 35 34 Maximum Capacity, k=2. Off-Cycle, Condition C 35 34 Compressor Off. Table 14—Test Operating Conditions for Variable- or Multiple-Capacity Low-Temperature Indoor Dedicated Condensing Units
Test title Suction
dew point,
°FReturn gas,
°FCondenser
air entering
dry-bulb,
°FCondenser
air entering
wet-bulb,
°F1Compressor operating mode Capacity, Condition A, Minimum Capacity −22 5 90 75 Minimum Capacity, k=1. Capacity, Condition A, Intermediate Capacity −22 5 90 75 Intermediate Capacity, k=i. Capacity, Condition A, Maximum Capacity −22 5 90 75 Maximum Capacity, k=2. Off-Cycle, Condition A 90 75 Compressor Off. Table 15—Test Operating Conditions for Two-Capacity Medium-Temperature Indoor Matched-Pair or Single-Packaged Refrigeration Systems
Test description Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering
relative
humidity, %Condenser
air entering
dry-bulb, °FCondenser
air entering wet-bulb, °FCompressor status Capacity, Condition A, Low Capacity 35 <50 90 1 75,2 65 Low Capacity. Capacity, Condition A, High Capacity 35 <50 90 1 75,2 65 High Capacity. Off-Cycle, Condition A 35 <50 90 1 75,2 65 Off. Table 16—Test Operating Conditions for Two Capacity Low-Temperature Indoor Matched-Pair or Single-Packaged Refrigeration Systems
Test description Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering
relative
humidity, %Condenser
air entering
dry-bulb, °FMaximum
condenser
air entering
wet-bulb, °FCompressor status Capacity, Condition A, Low Capacity −10 <50 90 1 75,265 Low Capacity. Capacity, Condition A, High Capacity −10 <50 90 1 75,2 65 High Capacity. Off-Cycle, Condition A −10 <50 90 1 75,2 65 Off. Defrost −10 <50 System Dependent. 3.2.6 Test Conditions for Variable- or Multiple-Capacity Indoor Matched Pair or Single-Packaged Refrigeration Systems
For variable- or multiple-capacity indoor medium-temperature matched-pair or single-packaged refrigeration systems, conduct tests using the test conditions specified in table 17 of this appendix. For variable- or multiple-capacity indoor low-temperature matched-pair or single-packaged refrigeration systems, conduct tests using the test conditions specified in table 18 of this appendix.
Table 17—Test Operating Conditions for Variable- or Multiple-Capacity Medium-Temperature Indoor Matched-Pair or Single-Packaged Refrigeration Systems
Test description Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering relative
humidity, %Condenser
air entering
dry-bulb, °FCondenser
air entering
wet-bulb, °FCompressor status Capacity, Condition A, Minimum Capacity 35 <50 90 1 75,2 65 Minimum Capacity. Capacity, Condition A, Intermediate Capacity 35 <50 90 1 75,2 65 Intermediate Capacity. Capacity, Condition A, High Capacity 35 <50 90 1 75,1 65 Maximum Capacity. Off-Cycle, Condition A 35 <50 90 1 75,2 65 Off. Table 18—Test Operating Conditions for Variable- or Multiple-Capacity Low-Temperature Indoor Matched-Pair or Single-Packaged Refrigeration Systems
Test description Unit cooler
air entering
dry-bulb, °FUnit cooler
air entering relative
humidity, %Condenser
air entering
dry-bulb, °FMaximum condenser
air entering
wet-bulb, °FCompressor status Capacity, Condition A, Minimum Capacity −10 <50 90 1 75,2 65 Minimum Capacity. Capacity, Condition A, Intermediate Capacity −10 <50 90 1 75,2 65 Intermediate Capacity. Capacity, Condition A, Maximum Capacity −10 <50 90 1 75,2 65 Maximum Capacity. Off-Cycle, Condition A −10 <50 90 1 75,2 65 Off. Defrost −10 <50 System Dependent. 3.3 Calculation for Walk-in Box Load
3.3.1 For medium- and low-temperature refrigeration systems with indoor condensing units, calculate walk-in box loads for high and low load periods as a function of net capacity as described in section 6.2.1 of AHRI 1250–2020.
3.3.2 For medium- and low-temperature refrigeration systems with outdoor condensing units, calculate walk-in box loads for high and low load periods as a function of net capacity and outdoor temperature as described in section 6.2.2 of AHRI 1250–2020.
3.3.3 For high-temperature refrigeration systems, calculate walk-in box load as follows.
ḂL = 0.5 · q̇ss,A
Where q̇ss,A is the measured net capacity for Test Condition A.
3.4 Calculation for Annual Walk-in Energy Factor (AWEF2)
Calculations used to determine AWEF2 based on performance data obtained for testing shall be as specified in section 7 of AHRI 1250–2020 with modifications as indicated in sections 3.4.7 through 3.4.10 of this appendix. Calculations used to determine AWEF2 for refrigeration systems not specifically identified in sections 7.1.1 through 7.1.6 of AHRI 1250–2020 are enumerated in sections 3.4.1 through 3.4.6 and 3.4.11 through 3.4.14 of this appendix.
3.4.1 Two-Capacity Condensing Units Tested Alone, Indoor
3.4.1.1 Unit Cooler Power
Calculate maximum-capacity unit cooler power during the compressor on period ĖFcomp,on, in Watts, using Equation 130 of AHRI 1250–2020 for medium-temperature refrigeration systems and using Equation 173 of AHRI 1250–2020 for low-temperature refrigeration systems.
Calculate unit cooler power during the compressor off period ĖFcomp,off, in Watts, as 20 percent of the maximum-capacity unit cooler power during the compressor on period.
3.4.1.2 Defrost
For freezer refrigeration systems, calculate defrost heat contribution Q̇DF in Btu/h and the defrost average power consumption ḊF in W as a function of steady-state maximum gross refrigeration capacity Q̇grossk=2, as specified in section C10.2.2 of Appendix C of AHRI 1250–2020.
3.4.1.3 Net Capacity
Calculate steady-state maximum net capacity, q̇ssk=2, and minimum net capacity, q̇ssk=1 as follows:
q̇ssk=2 = Q̇grossk=2 − 3412 · ĖFcomp,on
q̇ssk=1 = Q̇grossk=1 − 3412 · 0.2 · ĖFcomp,on
Where:
Q̇grossk=2 and Q̇grossk=1 represent gross refrigeration capacity at maximum and minimum capacity, respectively.
3.4.1.4 Calculate average power input during the low load period as follows.
If the low load period box load, BL̇L, plus defrost heat contribution, Q̇DF (only applicable for freezers), is less than the minimum net capacity q̇ssk=1:
Where:
Ėssk=1 is the steady state condensing unit power input for minimum-capacity operation.
Ėcu,off is the condensing unit off-cycle power input, measured as described in section C3.5 of AHRI 1250–2020.
If the low load period box load, BL̇L, plus defrost heat contribution, Q̇DF, (only applicable for freezers) is greater than the minimum net capacity q̇ssk=1:
3.4.1.5 Calculate average power input during the high load period as follows.
3.4.1.6 Calculate the AWEF2 as follows:
3.4.2 Variable-Capacity or Multistage Condensing Units Tested Alone, Indoor
3.4.2.1 Unit Cooler Power
Calculate maximum-capacity unit cooler power during the compressor on period ĖFcomp,on as described in section 3.4.1.1 of this appendix.
Calculate unit cooler power during the compressor off period ĖFcomp,off, in Watts, as 20 percent of the maximum-capacity unit cooler power during the compressor on period.
3.4.2.2 Defrost
Calculate Defrost parameters as described in section 4.4.1.2 of this appendix.
3.4.2.3 Net Capacity
Calculate steady-state maximum net capacity, q̇ssk=2, intermediate net capacity, q̇ssk=i, and minimum net capacity, q̇ssk=1 as follows:
q̇ssk=2 = Q̇grossk=2 − 3412 · ĖFcomp,on
q̇ssk=2 = Q̇grossk=2 − 3412 · Kf · ĖFcomp,on
q̇ssk=1 = Q̇grossk=1 − 3412 · 0.2 · ĖFcomp,on
Where:
Q̇grossk=2, Q̇grossk=i, Q̇gross,k=1, and represent gross refrigeration capacity at maximum, intermediate, and minimum capacity, respectively.
Kf is the unit cooler power coefficient for intermediate capacity operation, set equal to 0.2 to represent low-speed fan operation if the Duty Cycle for a Digital Compressor, the Speed Ratio for a Variable-Speed Compressor, or the Displacement Ratio for a Multi-Stage Compressor at Intermediate Capacity is 65% or less, and otherwise set equal to 1.0.
3.4.2.4 Calculate average power input during the low load period as follows.
If the low load period box load, BL̇L, plus defrost heat contribution Q̇DF (only applicable for freezers) is less than the minimum net capacity q̇ssk=1:
Where Ėcu,off, in W, is the condensing unit off-mode power consumption, measured as described in section C3.5 of AHRI 1250–2020.
If the low load period box load BL̇L plus defrost heat contribution Q̇DF (only applicable for freezers) is greater than the minimum net capacity q̇ssk=1 and less than the intermediate net capacity q̇ssk=i:
Where:
EERk=1 is the minimum-capacity energy efficiency ratio, equal to q̇ssk=1 divided by Ėssk=1 + 0.2 · ĖFcomp,on; and
EERk=i is the intermediate-capacity energy efficiency ratio, equal to q̇ssk=i divided by Ėssk=i + Kf · ĖFcomp,on.
3.4.2.5 Calculate average power input during the high load period as follows:
If the high load period box load, BL̇H, plus defrost heat contribution, Q̇DF (only applicable for freezers), is greater than the minimum net capacity q̇ssk=1 and less than the intermediate net capacity q̇ssk=i:
If the high load period box load, BL̇H, plus defrost heat contribution, Q̇DF (only applicable for freezers), is greater than the intermediate net capacity, q̇ssk=i, and less than the maximum net capacity, q̇ssk=2:
Where:
EERk=2 is the maximum-capacity energy efficiency ratio, equal to q̇ssk=2 divided by Ėssk=2 + ĖFcomp,on
3.4.2.6 Calculate the AWEF2 as follows.
3.4.3 Two-Capacity Condensing Units Tested Alone, Outdoor
3.4.3.1 Unit Cooler Power
Calculate maximum-capacity unit cooler power during the compressor on period ĖFcomp,on, in Watts, using Equation 153 of AHRI 1250–2020 for medium-temperature refrigeration systems and using Equation 196 of AHRI 1250–2020 for low-temperature refrigeration systems.
Calculate unit cooler power during the compressor off period ĖFcomp,off, in Watts, as 20 percent of the maximum-capacity unit cooler power during the compressor on period.
3.4.3.2 Defrost
Calculate Defrost parameters as described in section 3.4.1.2 of this appendix.
3.4.3.3 Condensing Unit Off-Cycle Power
Calculate Condensing Unit Off-Cycle Power for temperature tj as follows.
Where Ėcu,off,A and Ėcu,off,C are the Condensing Unit off-cycle power measurements for test conditions A and C, respectively, measured as described in section C3.5 of AHRI 1250–2020. If tj is greater than 35 °F and less than 59 °F, use Equation 157 of AHRI 1250–2020, and if tj is greater than or equal to 59 °F and less than 95 °F, use Equation 159 of AHRI 1250–2020.
3.4.3.4 Net Capacity and Condensing Unit Power Input
Calculate steady-state maximum net capacity, q̇ssk=2(tj), and minimum net capacity, q̇ssk=1(tj), and corresponding condensing unit power input levels Ėssk=2(tj) and Ėssk=1(tj) as a function of outdoor temperature tj as follows:
If tj ≤ 59 °F:
If 59 °F < tj:
Where:
The capacity level k can equal 1 or 2;
Q̇gross,Xk=2 and Q̇gross,Xk=1 represent gross refrigeration capacity at maximum and minimum capacity, respectively, for test condition X, which can take on values A, B, or C;
Ėss,Xk=2 and Ėss,Xk=1 represent condensing unit power input at maximum and minimum capacity, respectively for test condition X.
3.4.3.5 Calculate average power input during the low load period as follows.
Calculate the temperature, tIL, in the following equation which the low load period box load, BL̇L(tj), plus defrost heat contribution, Q̇DF (only applicable for freezers), is less than the minimum net capacity, q̇ssk=1(tj), by solving the following equation for tIL:
BL̇L (tIL) + Q̇DF = q̇ssk=1(tIL)
For tj < tIL:
Where Ėcu,off(tj), in W, is the condensing unit off-mode power consumption for temperature tj, determined as indicated in section 3.4.3.3 of this appendix.
For tj ≥ tIL:
3.4.3.6 Calculate average power input during the high load period as follows.
Calculate the temperature, tIH, in the following equation which the high load period box load, BL̇H(tj), plus defrost heat contribution, Q̇DF (only applicable for freezers), is less than the minimum net capacity, q̇ssk=1(tj) , by solving the following equation for tIH:
BL̇H (tIH) + Q̇DF = q̇ssk=1(tIH)
Calculate the temperature, tIIH, in the following equation which the high load period box load BL̇H(tj) plus defrost heat contribution Q̇DF (only applicable for freezers) is less than the maximum net capacity q̇ssk=2(tj), by solving the following equation for tIIH:
BL̇H (tIIH) + Q̇DF = q̇ssk=1(tIIH)
For tj < tIH:
For tIH ≤ tj < tIIH:
For tIIH ≤ tj:
ĖH (tj) = (Ėssk=2(tj) + ĖFcomp,on)
3.4.3.7 Calculate the AWEF2 as follows:
3.4.4 Variable-Capacity or Multistage Condensing Units Tested Alone, Outdoor
3.4.4.1 Unit Cooler Power
Calculate maximum-capacity unit cooler power during the compressor on period ĖFcomp,on as described in section 3.4.1.1 of this appendix.
Calculate unit cooler power during the compressor off period ĖFcomp,on, in Watts, as 20 percent of the maximum-capacity unit cooler power during the compressor on period.
3.4.4.2 Defrost
Calculate Defrost parameters as described in section 3.4.1.2 of this appendix.
3.4.4.3 Condensing Unit Off-Cycle Power
Calculate Condensing Unit Off-Cycle Power for temperature, tj, as described in section 3.4.3.3 of this appendix.
3.4.4.4 Net Capacity and Condensing Unit Power Input
Calculate steady-state maximum net capacity, q̇ssk=2(tj), intermediate net capacity, q̇ssk=i(tj) , and minimum net capacity, q̇ssk=1(tj), and corresponding condensing unit power input levels Ėssk=2(tj), Ėssk=i(tj), Ėssk=1(tj) and as a function of outdoor temperature, tj, as follows:
If tj ≤ 59 °F:
If 59 °F < tj:
Where:
The capacity level k can equal 1, i, or 2;
Q̇gross,Xk=2, Q̇gross,Xk=i and Q̇gross,Xk=1 represent gross refrigeration capacity at maximum, intermediate, and minimum capacity, respectively, for test condition X, which can take on values A, B, or C;
Ėss,Xk=2 and Ėss,Xk=1 represent condensing unit power input at maximum and minimum capacity, respectively for test condition X; and
Kf is the unit cooler power coefficient for intermediate capacity operation, set equal to 0.2 to represent low-speed fan operation if the Duty Cycle for a Digital Compressor, the Speed Ratio for a Variable-Speed Compressor, or the Displacement Ratio for a Multi-Stage Compressor at Intermediate Capacity is 65% or less, and otherwise set equal to 1.0.
3.4.4.5 Calculate average power input during the low load period as follows.
Calculate the temperature, tIL, in the following equation which the low load period box load BL̇L(tj) plus defrost heat contribution, Q̇DF (only applicable for freezers), is less than the minimum net capacity, q̇ssk=1(tj), by solving the following equation for tIL:
BL̇L (tIL) + Q̇DF = q̇ssk=1(tIL)
Calculate the temperature, tVL, in the following equation which the low load period box load, BL̇L(tj), plus defrost heat contribution, Q̇DF (only applicable for freezers), is less than the intermediate net capacity, q̇ssk=i(tj), by solving the following equation for tVL:
BL̇L (tVL) + Q̇DF = q̇ssk=i(tVL)
For tj < tIL:
Where, Ėcu,off(tj) in W, is the condensing unit off-mode power consumption for temperature, tj, determined as indicated in section 3.4.3.3 of this appendix.
For tIL ≤ tj < tVL:
For tVL ≤ tj:
Where:
EERk=2(tj) is the minimum-capacity energy efficiency ratio, equal to q̇ssk=1(tj) divided by Ėssk=1(tj) + 0.2 ĖFcomp,on;
EERk=i(tj) is the intermediate-capacity energy efficiency ratio, equal to q̇ssk=i(tj) divided by Ėssk=i(tj) + Kf · ĖFcomp,on; and
EERk=2(tj) is the maximum-capacity energy efficiency ratio, equal to q̇ssk=2(tj) divided by Ėssk=2(tj) + ĖFcomp,on
3.4.4.6 Calculate average power input during the high load period as follows.
Calculate the temperature tVH in the following equation which the high load period box load BL̇H(tj) plus defrost heat contribution Q̇DF (only applicable for freezers) is less than the intermediate net capacity q̇ssk=i(tj), by solving the following equation for tVH:
BL̇H (tVH) + Q̇DF = q̇ssk=i(tVH)
Calculate the temperature tIIH in the following equation which the high load period box load BL̇H(tj) plus defrost heat contribution Q̇DF (only applicable for freezers) is less than the maximum net capacity q̇ssk=2(tj), by solving the following equation for tIIH:
BL̇H (tIIH) + Q̇DF = q̇ssk=2(tIIH)
For tj < tVH:
For tVH ≤ tj < tIIH:
For tIIH ≤ tj:
ĖH (tj) = (Ėssk=2 (tj) + ĖFcomp,on)
3.4.4.7 Calculate the AWEF2 as follows:
3.4.5 Two-Capacity Indoor Matched Pairs or Single-Packaged Refrigeration Systems Other Than High-Temperature
3.4.5.1 Defrost
For freezer refrigeration systems, defrost heat contribution Q̇DF in Btu/h and the defrost average power consumption ḊF in W shall be as measured in accordance with section C10.2.1 of Appendix C of AHRI 1250–2020.
3.4.5.2 Calculate average power input during the low load period as follows.
If the low load period box load BL̇L plus defrost heat contribution Q̇DF (only applicable for freezers) is less than the minimum net capacity q̇ssk=1:
Where:
q̇ssk=1 and Ėssk=1 are the steady state refrigeration system minimum net capacity, in Btu/h, and associated refrigeration system power input, in W, respectively, for minimum-capacity operation, measured as described in AHRI 1250–2020.
ĖFcomp,off and Ėcu,off, both in W, are the unit cooler and condensing unit, respectively, off-mode power consumption, measured as described in section C3.5 of AHRI 1250–2020.
If the low load period box load BL̇L plus defrost heat contribution Q̇DF (only applicable for freezers) is greater than the minimum net capacity q̇ssk=1:
Where q̇ssk=2 and Ėssk=2 are the steady state refrigeration system maximum net capacity, in Btu/h, and associated refrigeration system power input, in W, respectively, for maximum-capacity operation, measured as described in AHRI 1250–2020.
3.4.5.3 Calculate average power input during the high load period as follows.
3.4.5.4 Calculate the AWEF2 as follows:
3.4.6 Variable-Capacity or Multistage Indoor Matched Pairs or Single-Packaged Refrigeration Systems Other Than High-Temperature
3.4.6.1 Defrost
For freezer refrigeration systems, defrost heat contribution Q̇DF in Btu/h and the defrost average power consumption ḊF in W shall be as measured in accordance with section C10.2.1 of Appendix C of AHRI 1250–2020.
3.4.6.2 Calculate average power input during the low load period as follows.
If the low load period box load BL̇L plus defrost heat contribution Q̇DF (only applicable for freezers) is less than the minimum net capacity q̇ssk=1:
Where:
q̇ssk=1 and Ėssk=1 are the steady state refrigeration system minimum net capacity, in Btu/h, and associated refrigeration system power input, in W, respectively, for minimum-capacity operation, measured as described in AHRI 1250–2020; and
ĖFcomp,off and Ėcu,off, both in W, are the unit cooler and condensing unit, respectively, off-mode power consumption, measured as described in section C3.5 of AHRI 1250–2020.
If the low load period box load BL̇L plus defrost heat contribution Q̇DF (only applicable for freezers) is greater than the minimum net capacity and less than the intermediate net capacity q̇ssk=i:
Where:
EERk=1 is the minimum-capacity energy efficiency ratio, equal to q̇ssk=1divided by Ėssk=1;
q̇ssk=i and Ėssk=i are the steady state refrigeration system intermediate net capacity, in Btu/h, and associated refrigeration system power input, in W, respectively, for intermediate-capacity operation, measured as described in AHRI 1250–2020.
EERk=i is the intermediate-capacity energy efficiency ratio, equal to q̇ssk=i divided by Ėssk=i.
3.4.6.3 Calculate average power input during the high load period as follows.
If the high load period box load BL̇H plus defrost heat contribution Q̇DF (only applicable for freezers) is greater than the minimum net capacity q̇ssk=1 and less than the intermediate net capacity q̇ssk=i:
If the high load period box load BL̇H plus defrost heat contribution Q̇DF (only applicable for freezers) is greater than the intermediate net capacity q̇ssk=i and less than the maximum net capacity q̇ssk=2:
Where:
q̇ssk=2 and Ėssk=2 are the steady state refrigeration system maximum net capacity, in Btu/h, and associated refrigeration system power input, in W, respectively, for maximum-capacity operation, measured as described in AHRI 1250–2020; and
EERk=2 is the maximum-capacity energy efficiency ratio, equal to q̇ssk=2 divided by Ėssk=2.
3.4.6.4 Calculate the AWEF2 as follows.
3.4.7 Variable-Capacity or Multistage Outdoor Matched Pairs or Single-Packaged Refrigeration Systems Other Than High-Temperature
Calculate AWEF2 as described in section 7.6 of AHRI 1250–2020, with the following revisions.
3.4.7.1 Condensing Unit Off-Cycle Power
Calculate condensing unit off-cycle power for temperature tj as indicated in section 3.4.3.3 of this appendix. Replace the constant value ĖCU,off in Equations 55 and 70 of AHRI 1250–2020 with the values ĖCU,off(tj), which vary with outdoor temperature tj.
3.4.7.2 Unit Cooler Off-Cycle Power
Set unit cooler Off-Cycle power ĖFcomp,off equal to the average of the unit cooler off-cycle power measurements made for test conditions A, B, and C.
3.4.7.3 Average Power During the Low Load Period
Calculate average power for intermediate-capacity compressor operation during the low load period Ėss,Lk=v(tj) as described in section 7.6 of AHRI 1250–2020, except that, instead of calculating intermediate-capacity compressor EER using Equation 77 of AHRI 1250–2020, calculate EER as follows.
For tj < tVL:
For tVL ≤ tj:
Where:
EERk=1(tj) is the minimum-capacity energy efficiency ratio, equal to q̇ssk=1(tj) divided by Ėssk=1(tj);
EERk=i(tj) is the intermediate-capacity energy efficiency ratio, equal to q̇ssk=i (tj) divided by Ėssk=i(tj); and
EERk=2(tj) is the maximum-capacity energy efficiency ratio, equal to q̇ssk=2(tj) divided by Ėssk=2(tj)
3.4.7.4 Average Power During the High Load Period
Calculate average power for intermediate-capacity compressor operation during the high load period Ėss,Hk=v(tj) as described in section 7.6 of AHRI 1250–2020, except that, instead of calculating intermediate-capacity compressor EER using Equation 61 of AHRI 1250–2020, calculate EER as follows:
For tj < tVH:
For tVH ≤ tj:
3.4.8 Two-Capacity Outdoor Matched Pairs or Single-Packaged Refrigeration Systems Other Than High-Temperature
Calculate AWEF2 as described in section 7.5 of AHRI 1250–2020, with the following revisions for Condensing Unit Off-Cycle Power and Unit Cooler Off-Cycle Power. Calculate condensing unit off-cycle power for temperature tj as indicated in section 3.4.3.3 of this appendix. Replace the constant value ĖCU,off in Equations 13 and 29 of AHRI 1250–2020 with the values ĖCU,off(tj), which vary with outdoor temperature tj. Set unit cooler Off-Cycle power ĖFcomp,off equal to the average of the unit cooler off-cycle power measurements made for test conditions A, B, and C.
3.4.9 Single-Capacity Outdoor Matched Pairs or Single-Packaged Refrigeration Systems Other Than High-Temperature
Calculate AWEF2 as described in section 7.4 of AHRI 1250–2020, with the following revision for Condensing Unit Off-Cycle Power and Unit Cooler Off-cycle Power. Calculate condensing unit off-cycle power for temperature tj as indicated in section 3.4.3.3 of this appendix. Replace the constant value ĖCU,off in Equations 13 of AHRI 1250–2020 with the values ĖCU,off(tj), which vary with outdoor temperature tj. Set unit cooler Off-Cycle power ĖFcomp,off equal to the average of the unit cooler off-cycle power measurements made for test conditions A, B, and C.
3.4.10 Single-Capacity Condensing Units, Outdoor
Calculate AWEF2 as described in section 7.9 of AHRI 1250–2020, with the following revision for Condensing Unit Off-Cycle Power. Calculate condensing unit off-cycle power for temperature tj as indicated in section 3.4.3.3 of this appendix rather than as indicated in Equations 157, 159, 202, and 204 of AHRI 1250–2020.
3.4.11 High-Temperature Matched Pairs or Single-Packaged Refrigeration Systems, Indoor
3.4.11.1 Calculate Load Factor LF as follows:
Where:
ḂL , in Btu/h is the non-equipment-related box load calculated as described in section 3.3.3 of this appendix;
ĖFcomp,off , in W, is the unit cooler off-cycle power consumption, equal to 0.1 times the unit cooler on-cycle power consumption; and
q̇ss,A, in Btu/h is the measured net capacity for test condition A.
3.4.11.2 Calculate the AWEF2 as follows:
Where:
Ėss,A , in W, is the measured system power input for test condition A; and
Ėcu,off , in W, is the condensing unit off-cycle power consumption, measured as described in section C3.5 of AHRI 1250–2020.
3.4.12 High-Temperature Matched Pairs or Single-Packaged Refrigeration Systems, Outdoor
3.4.12.1 Calculate Load Factor LF(tj) for outdoor temperature tj as follows:
Where:
ḂL , in Btu/h, is the non-equipment-related box load calculated as described in section 3.3.3 of this appendix;
ĖFcomp,off , in W, is the unit cooler off-cycle power consumption, equal to 0.1 times the unit cooler on-cycle power consumption; and
q̇ss(tj), in Btu/h, is the net capacity for outdoor temperature tj, calculated as described in section 7.4.2 of AHRI 1250–2020.
3.4.12.2 Calculate the AWEF2 as follows:
Where:
E ̇ss(tj), in W, is the system power input for temperature tj, calculated as described in section 7.4.2 of AHRI 1250–2020;
E ̇cu,off, in W, is the condensing unit off-cycle power consumption, measured as described in section C3.5 of AHRI 1250–2020; and
nj are the hours for temperature bin j.
3.4.13 High-Temperature Unit Coolers Tested Alone
3.4.13.1 Calculate Refrigeration System Power Input as follows:
Where:
q̇mix,evap, in W, is the net evaporator capacity, measured as described in AHRI 1250–2020;
ĖFcomp,on , in W, is the unit cooler on-cycle power consumption; and
EER, in W, equals
3.4.13.2 Calculate the load factor LF as follows:
Where:
ḂL , in Btu/h, is the non-equipment-related box load calculated as described in section 3.3.3 of this appendix; and
ĖFcomp,off , in W, is the unit cooler off-cycle power consumption, equal to 0.1 times the unit cooler on-cycle power consumption.
3.4.13.3 Calculate AWEF2 as follows:
3.4.14 CO2 Unit Coolers Tested Alone
Calculate AWEF2 for CO2 Unit Coolers Tested Alone using the calculations specified in in section 7.8 of AHRI 1250–2020 for calculation of AWEF2 for Unit Cooler Tested Alone.
3.5 Test Method
Test the Refrigeration System in accordance with AHRI 1250–2020 to determine refrigeration capacity and power input for the specified test conditions, with revisions and additions as described in this section.
3.5.1 Chamber Conditioning Using the Unit Under Test
In Appendix C, section C5.2.2 of AHRI 1250–2020, for applicable system configurations (matched pairs, single-packaged refrigeration systems, and standalone unit coolers), the unit under test may be used to aid in achieving the required test chamber conditions prior to beginning any steady state test. However, the unit under test must be inspected and confirmed to be free from frost before initiating steady state testing.
3.5.2 General Modification: Methods of Testing
3.5.2.1 Refrigerant Temperature Measurements
When testing a condensing unit alone, measure refrigerant liquid temperature leaving the condensing unit, and the refrigerant vapor temperature entering the condensing unit as required in section C7.5.1.1.2 of Appendix C of AHRI 1250–2020 using the same measurement approach specified for the unit cooler in section C3.1.3 of Appendix C of AHRI 1250–2020. In all cases in which thermometer wells or immersed sheathed sensors are prescribed, if the refrigerant tube outer diameter is less than 1⁄2 inch, the refrigerant temperature may be measured using the average of two temperature measuring instruments with a minimum accuracy of ±0.5 °F placed on opposite sides of the refrigerant tube surface—resulting in a total of up to 8 temperature measurement devices used for the DX Dual Instrumentation method. In this case, the refrigerant tube shall be insulated with 1-inch thick insulation from a point 6 inches upstream of the measurement location to a point 6 inches downstream of the measurement location. Also, to comply with this requirement, the unit cooler/evaporator entering measurement location may be moved to a location 6 inches upstream of the expansion device and, when testing a condensing unit alone, the entering and leaving measurement locations may be moved to locations 6 inches from the respective service valves.
3.5.2.2 Mass Flow Meter Location
When using the DX Dual Instrumentation test method of AHRI 1250–2020, applicable for unit coolers, dedicated condensing units, and matched pairs, the second mass flow meter may be installed in the suction line as shown in Figure C1 of AHRI 1250–2020.
3.5.2.3 Subcooling at Refrigerant Mass Flow Meter
In section C3.4.5 of Appendix C of AHRI 1250–2020, when verifying subcooling at the mass flow meters, only the sight glass and a temperature sensor located on the tube surface under the insulation are required. Subcooling shall be verified to be within the 3 °F requirement downstream of flow meters located in the same chamber as a condensing unit under test and upstream of flow meters located in the same chamber as a unit cooler under test, rather than always downstream as indicated in AHRI 1250–2009, section C3.4.5. If the subcooling is less than 3 °F when testing a unit cooler, dedicated condensing unit, or matched pair (not a single-packaged system), cool the line between the condensing unit outlet and this location to achieve the required subcooling. When providing such cooling while testing a matched pair (a) set up the line-cooling system and also set up apparatus to heat the liquid line between the mass flow meters and the unit cooler, (b) when the system has achieved steady state without activation of the heating and cooling systems, measure the liquid temperature entering the expansion valve for a period of at least 30 minutes, (c) activate the cooling system to provide the required subcooling at the mass flow meters, (d) if necessary, apply heat such that the temperature entering the expansion valve is within 0.5 °F of the temperature measured during step (b), and (e) proceed with measurements once condition (d) has been verified.
3.5.2.4 Installation Instructions
Manufacturer installation instructions or installation instructions described in this section refer to the instructions that come packaged with or appear on the labels applied to the unit. This does not include online manuals.
Installation Instruction Hierarchy: If a given installation instruction provided on the label(s) applied to the unit conflicts with the installation instructions that are shipped with the unit, the label takes precedence. For testing of matched pairs, the installation instructions for the dedicated condensing unit shall take precedence. Setup shall be in accordance with the field installation instructions (laboratory installation instructions shall not be used). Achieving test conditions shall always take precedence over installation instructions.
3.5.2.5. Refrigerant Charging and Adjustment of Superheat and Subcooling.
All dedicated condensing systems (dedicated condensing units tested alone, matched pairs, and single packaged dedicated systems) that use flooding of the condenser for head pressure control during low-ambient-temperature conditions shall be charged, and superheat and/or subcooling shall be set, at Refrigeration C test conditions unless otherwise specified in the installation instructions.
If after being charged at Refrigeration C condition the unit under test does not operate at the Refrigeration A condition due to high pressure cut out, refrigerant shall be removed in increments of 4 ounces or 5 percent of the test unit's receiver capacity, whichever quantity is larger, until the unit operates at the Refrigeration A condition. All tests shall be run at this final refrigerant charge. If less than 0 °F of subcooling is measured for the refrigerant leaving the condensing unit when testing at B or C condition, calculate the refrigerant-enthalpy-based capacity (i.e., when using the DX dual instrumentation, the DX calibrated box, or single-packaged unit refrigerant enthalpy method) assuming that the refrigerant is at saturated liquid conditions at the condensing unit exit.
All dedicated condensing systems that do not use a flooded condenser design shall be charged at Refrigeration A test conditions unless otherwise specified in the installation instructions.
If the installation instructions give a specified range for superheat, sub-cooling, or refrigerant pressure, the average of the range shall be used as the refrigerant charging parameter target and the test condition tolerance shall be ±50 percent of the range. Perform charging of near-azeotropic and zeotropic refrigerants only with refrigerant in the liquid state. Once the correct refrigerant charge is determined, all tests shall run until completion without further modification.
3.5.2.5.1. When charging or adjusting superheat/subcooling, use all pertinent instructions contained in the installation instructions to achieve charging parameters within the tolerances. However, in the event of conflicting charging information between installation instructions, follow the installation instruction hierarchy listed in section 3.5.2.4. Conflicting information is defined as multiple conditions given for charge adjustment where all conditions specified cannot be met. In the event of conflicting information within the same set of charging instructions (e.g., the installation instructions shipped with the dedicated condensing unit), follow the hierarchy in Table 19 for priority. Unless the installation instructions specify a different charging tolerance, the tolerances identified in table 19 of this appendix shall be used.
Table 19—Test Condition Tolerances and Hierarchy for Refrigerant Charging and Setting of Refrigerant Conditions
Priority Fixed orifice Expansion Valve Parameter with installation
instruction targetTolerance Parameter with installation
instruction targetTolerance 1 Superheat ±2.0 °F Subcooling 10% of the Target Value; No less than ±0.5 °F, No more than ±2.0 °F 2 High Side Pressure or Saturation Temperature* ±4.0 psi or ±1.0 °F High Side Pressure or Saturation Temperature* ±4.0 psi or
±1.0 °F3 Low Side Pressure or Saturation Temperature* ±2.0 psi or ±0.8 °F Superheat ±2.0 °F 4 Low Side Temperature ±2.0 °F Low Side Pressure or Saturation Temperature * ±2.0 psi or
±0.8 °F5 High Side Temperature ±2.0 °F Approach Temperature ±1.0 °F 6 Charge Weight ±2.0 oz Charge Weight 0.5% or 1.0 oz, whichever is greater 3.5.2.5.2. Dedicated Condensing Unit.
If the Dedicated Condensing Unit includes a receiver and the subcooling target leaving the condensing unit provided in installation instructions cannot be met without fully filling the receiver, the subcooling target shall be ignored. Likewise, if the Dedicated Condensing unit does not include a receiver and the subcooling target leaving the condensing unit cannot be met without the unit cycling off on high pressure, the subcooling target can be ignored. Also, if no instructions for charging or for setting subcooling leaving the condensing unit are provided in the installation instructions, the refrigeration system shall be set up with a charge quantity and/or exit subcooling such that the unit operates during testing without shutdown (e.g., on a high-pressure switch) and operation of the unit is otherwise consistent with the requirements of the test procedure of this appendix and the installation instructions.
3.5.2.5.3. Unit Cooler. Use the shipped expansion device for testing. Otherwise, use the expansion device specified in the installation instructions. If the installation instructions specify multiple options for the expansion device, any specified expansion device may be used. The supplied expansion device shall be adjusted until either the superheat target is met, or the device reaches the end of its adjustable range. In the event the device reaches the end of its adjustable range and the super heat target is not met, test with the adjustment at the end of its range providing the closest match to the superheat target, and the test condition tolerance for super heat target shall be ignored. The measured superheat is not subject to a test operating tolerance. However, if the evaporator exit condition is used to determine capacity using the DX dual instrumentation method or the refrigerant enthalpy method, individual superheat value measurements may not be equal to or less than zero. If this occurs, or if the operating tolerances of measurements affected by expansion device fluctuation are exceeded, the expansion device shall be replaced, operated at an average superheat value higher than the target, or both, in order to avoid individual superheat value measurements less than zero and/or to meet the required operating tolerances.
3.5.2.5.4. Single-Packaged Unit. Unless otherwise directed by the installation instructions, install one or more refrigerant line pressure gauges during the setup of the unit, located depending on the parameters used to verify or set charge, as described in this section:
3.5.2.5.4.1. Install a pressure gauge in the liquid line if charging is on the basis of subcooling, or high side pressure or corresponding saturation or dew point temperature.
3.5.2.5.4.2. Install a pressure gauge in the suction line if charging is on the basis of superheat, or low side pressure or corresponding saturation or dew point temperature. Install this gauge as close to the evaporator as allowable by the installation instructions and the physical constraints of the unit. Use methods for installing pressure gauge(s) at the required location(s) as indicated in the installation instructions if specified.
3.5.2.5.4.3. If the installation instructions indicate that refrigerant line pressure gauges should not be installed and the unit fails to operate due to high-pressure or low-pressure compressor cut off, then a charging port shall be installed, and the unit shall be evacuated of refrigerant and charged to the nameplate charge.
3.5.2.6 Ducted Units
For systems with ducted evaporator air, or that can be installed with or without ducted evaporator air: Connect ductwork on both the inlet and outlet connections and determine external static pressure (ESP) as described in sections 6.4 and 6.5 of ANSI/ASHRAE 37. Use pressure measurement instrumentation as described in section 5.3.2 of ANSI/ASHRAE 37. Test at the fan speed specified in the installation instructions—if there is more than one fan speed setting and the installation instructions do not specify which speed to use, test at the highest speed. Conduct tests with the ESP equal to 50% of the maximum ESP allowed in the installation instructions, within a tolerance of −0.00/+0.05 inches of water column. If the installation instructions do not provide the maximum ESP, the ESP shall be set for testing such that the air volume rate is 2⁄3 of the air volume rate measured when the ESP is 0.00 inches of water column within a tolerance of −0.00/+0.05 inches of water column.
If testing using either the indoor or outdoor air enthalpy method to measure the air volume rate, adjust the airflow measurement apparatus fan to set the external static pressure—otherwise, set the external static pressure by symmetrically restricting the outlet of the test duct. In case of conflict, these requirements for setting airflow take precedence over airflow values specified in manufacturer installation instructions or product literature.
3.5.2.7. Two-Speed or Multiple-Speed Evaporator Fans. Two-Speed or Multiple-Speed evaporator fans shall be considered to meet the qualifying control requirements of section C4.2 of Appendix C of AHRI 1250–2020 for measuring off-cycle fan energy if they use a fan speed no less than 50% of the speed used in the maximum capacity tests.
3.5.2.8. Defrost
Use section C10.2.1 of Appendix C of AHRI 1250–2020 for defrost testing. The Test Room Conditioning Equipment requirement of section C10.2.1.1 of Appendix C of AHRI 1250–2020 does not apply.
3.5.2.8.1 Adaptive Defrost
When testing to certify compliance to the energy conservation standards, use NDF = 4, as instructed in section C10.2.1.7 or C10.2.2.1 of AHRI 1250–2020. When determining the represented value of the calculated benefit for the inclusion of adaptive defrost, use NDF = 2.5, as instructed in section C10.2.1.7 or C10.2.2.1 of AHRI 1250–2020.
3.5.2.8.2 Hot Gas Defrost
When testing to certify compliance to the energy conservation standards, remove the hot gas defrost mechanical components and disconnect all such components from electrical power. Test the units as if they are electric defrost units, but do not conduct the defrost tests described in section C10.2.1 of AHRI 1250–2020. Use the defrost heat and power consumption values as described in section C10.2.2 of AHRI 1250–2020 for the AWEF2 calculations.
3.5.2.9 Dedicated condensing units that are not matched for testing and are not single-packaged dedicated systems.
The temperature measurement requirements of sections C3.1.3 and C4.1.3.1 appendix C of AHRI 1250–2020 shall apply only to the condensing unit exit rather than to the unit cooler inlet and outlet, and they shall be applied for two measurements when using the DX Dual Instrumentation test method.
3.5.2.10. Single-packaged dedicated systems
Use the test method in section C9 of appendix C of AHRI 1250–2020 (including the applicable provisions of ASHRAE 16–2016, ASHRAE 23.1–2010, ASHRAE 37–2009, and ASHRAE 41.6–2014, as referenced in section C9.1 of AHRI 1250–2020) as the method of test for single-packaged dedicated systems, with modifications as described in this section. Use two test methods listed in table 20 of this appendix to calculate the net capacity and power consumption. The test method listed with a lower “Hierarchy Number” and that has “Primary” as an allowable use in table 20 of this appendix shall be considered the primary measurement and used as the net capacity.
Table 20—Single-Packaged Methods of Test and Hierarchy
Hierarchy number Method of test Test hierarchy 1 Balanced Ambient Indoor Calorimeter Primary. 2 Indoor Air Enthalpy Primary or Secondary. 3 Indoor Room Calorimeter Primary or Secondary. 4 Calibrated Box Primary or Secondary. 5 Balanced Ambient Outdoor Calorimeter Secondary. 6 Outdoor Air Enthalpy Secondary. 7 Outdoor Room Calorimeter Secondary. 8 Single-Packaged Refrigerant Enthalpy1 Secondary. 9 Compressor Calibration Secondary. 3.5.2.10.1 Single-Packaged Refrigerant Enthalpy Method
The single-packaged refrigerant enthalpy method shall follow the test procedure of the DX Calibrated Box method in AHRI 1250–2020, appendix C, section C8 for refrigerant-side measurements with the following modifications:
3.5.2.10.1.1 Air-side measurements shall follow the requirements of the primary single-packaged method listed in table 20 of this appendix. The air-side measurements and refrigerant-side measurements shall be collected over the same intervals.
3.5.2.10.1.2 A preliminary test at Test Rating Condition A is required using the primary method prior to any modification necessary to install the refrigerant-side measuring instruments. Install surface mount temperature sensors on the evaporator and condenser coils at locations not affected by liquid subcooling or vapor superheat (i.e., near the midpoint of the coil at a return bend), entering and leaving the compressor, and entering the expansion device. These temperature sensors shall be included in the regularly recorded data.
3.5.2.10.1.3 After the preliminary test is completed, the refrigerant shall be removed from the equipment and the refrigerant-side measuring instruments shall be installed. The equipment shall then be evacuated and recharged with refrigerant. Once the equipment is operating at Test Condition A, the refrigerant charge shall be adjusted until, as compared to the average values from the preliminary test, the following conditions are achieved:
(a) Each on-coil temperature sensor indicates a reading that is within ±1.0 °F of the measurement in the initial test,
(b) The temperatures of the refrigerant entering and leaving the compressor are within ±4 °F, and
(c) The refrigerant temperature entering the expansion device is within ±1 °F.
3.5.2.10.1.4 Once these conditions have been achieved over an interval of at least 10 minutes, refrigerant charging equipment shall be removed and the official tests shall be conducted.
3.5.2.10.1.5 The lengths of liquid line to be added shall be 5 feet maximum, not including the requisite flow meter. This maximum length applies to each circuit separately.
3.5.2.10.1.6 Use section C9.2 of appendix C of AHRI 1250–2020 for allowable refrigeration capacity heat balance. Calculate the single-packaged refrigerant enthalpy (secondary) method test net capacity
Q̇net,secondary as follows: Q̇net,secondary = Q̇ref-3.412·ĖFcomp,on−Q̇sploss
Where:
Q̇ref is the gross capacity;
ĖFcomp,on is the evaporator compartment on-cycle power, including evaporator fan power; and
Q̇sploss is a duct loss calculation applied to the evaporator compartment of the single-packaged systems, which is calculated as indicated in the following equation.
Q̇sploss = UAcond × (Tevapside − Tcondside) + UAamb × (Tevapside − Tamb)
Where:
UAcond and UAamb are, for the condenser/evaporator partition and the evaporator compartment walls exposed to ambient air, respectively, the product of the overall heat transfer coefficient and surface area of the unit as manufactured, i.e. without external insulation that might have been added during the test. The areas shall be calculated based on measurements, and the thermal resistance values shall be based on insulation thickness and insulation material;
Tevapside is the air temperature in the evaporator compartment—the measured evaporator air inlet temperature may be used;
Tcondside is the air temperature in the condenser compartment—the measured chamber ambient temperature may be used, or a measurement may be made using a temperature sensor placed inside the condenser box at least 6 inches distant from any part of the refrigeration system; and
Tamb is the air temperature outside the single-packaged system.
3.5.2.10.1.7 For multi-circuit single-packaged systems utilizing the single-packaged refrigerant enthalpy method, apply the test method separately for each circuit and sum the separately-calculated refrigerant-side gross refrigeration capacities.
3.5.2.10.2 Calibrated Box Test Procedure
3.5.2.10.2.1 Measurements. Refer to section C3 of AHRI 1250–2020 (including the applicable provisions of ASHRAE 41.1–2013, ASHRAE 41.3–2014, and ASHRAE 41.10–2013, as referenced in section C3 of AHRI 1250–2020) for requirements of air-side and refrigerant-side measurements.
3.5.2.10.2.2 Apparatus setup for Calibrated Box Calibration and Test. Refer to section C5 of AHRI 1250–2020 and section C8 of AHRI 1250–2020 for specific test setup.
3.5.2.10.2.3 The calibrated box shall be installed in a temperature-controlled enclosure in which the temperature can be maintained at a constant level. When using the calibrated box method for Single-Packaged Dedicated Systems, the enclosure air temperature shall be maintained such that the condenser air entering conditions are as specified for the test.
3.5.2.10.2. The temperature-controlled enclosure shall be of a size that will provide clearances of not less than 18 in at all sides, top and bottom, except that clearance of any one surface may be reduced to not less than 5.5 inches.
3.5.2.10.2.5 The heat leakage of the calibrated box shall be noted in the test report.
3.5.2.10.2.6 Refrigerant lines within the calibrated box shall be well insulated to avoid appreciable heat loss or gain.
3.5.2.10.2.7 Instruments for measuring the temperature around the outside of the calibrated box to represent the enclosure temperature Ten shall be located at the center of each wall, ceiling, and floor. Exception: in the case where a clearance around the outside of the calibrated box, as indicated in section 3.5.2.10.2.4 of this appendix, is reduced to less than 18 inches, the number of temperature measuring devices on the outside of that surface shall be increased to six, which shall be treated as a single temperature to be averaged with the temperature of each of the other five surfaces. The six temperature measuring instruments shall be located at the center of six rectangular sections of equal area. If the refrigeration system is mounted at the location that would cover the center of the face on which it is mounted, up to four temperature measurements shall be used on that face to represent its temperature. Each sensor shall be aligned with the center of the face's nearest outer edge and centered on the distance between that edge and the single-packaged unit (this is illustrated in figure C5 of this section when using surface temperature sensors), and they shall be treated as a single temperature to be averaged with the temperature of each of the other five surfaces. However, any of these sensors shall be omitted if either
(a) the distance between the outer edge and the single-packaged unit is less than one foot or
(b) if the sensor location would be within two feet of any of the foot square surfaces discussed in section 3.5.2.10.2.8 of this appendix representing a warm discharge air impingement area. In this case, the remaining sensors shall be used to represent the average temperature for the surface.
3.5.2.10.2.8 One of the following two approaches shall be used for the box external temperature measurement. Box calibration and system capacity measurement shall both be done using the same one of these approaches. 1: Air temperature sensors. Each temperature sensor shall be at a distance of 6 inches from the calibrated box. If the clearance from a surface of the box (allowed for one surface only) is less than 12 inches, the temperature measuring instruments shall be located midway between the outer wall of the calibrated box and the adjacent surface. 2: Surface temperature sensors. Surface temperature sensors shall be mounted on the calibrated box surfaces to represent the enclosure temperature, Ten.
3.5.2.10.2.9 Additional surface temperature sensors may be used to measure external hot spots during refrigeration system testing. If this is done, two temperature sensors shall be used to measure the average temperature of the calibrated box surface covered by the condensing section—they shall be located centered on equal-area rectangles comprising the covered calibrated box surface whose common sides span the short dimension of this surface. Additional surface temperature sensors may be used to measure box surfaces on which warm condenser discharge air impinges. A pattern of square surfaces measuring one foot square shall be mapped out to represent the hot spot upon which the warm condenser air impinges. One temperature sensor shall be used to measure surface temperature at the center of each square (see figure C5 of this section). A drawing showing this pattern and identifying the surface temperature sensors shall be provided in the test report. The average surface temperature of the overall calibrated box outer surface during testing shall be calculated as follows.
Where:
Ai is the surface area of the ith of the six calibrated box surfaces;
Ti is the average temperature measured for the ith surface;
Aj is half of the surface area of the calibrated box covered by the condensing section;
T'j is the jth of the two temperature measurements underneath the condensing section;
T1 is the average temperature of the four or fewer measurements representing the temperature of the face on which the single-packaged system is mounted, prior to adjustments associated with hot spots based on measurements Tj and/or Tk;
Ak is the area of the kth of n 1-square-foot surfaces used to measure the condenser discharge impingement area hot spot; and,
T” k is the kth of the n temperature measurements of the condenser discharge impingement area hot spot.
Figure C5: Illustration of Layout of Surface Temperature Sensors on Face of Calibrated Box on which Single-Packaged Dedicated System is Mounted when Using Section 3.5.2.10.2.7 of Appendix C to this Part.3.5.2.10.2.10 Heating means inside the calibrated box shall be shielded or installed in a manner to avoid radiation to the Single-Packaged Dedicated System, the temperature measuring instruments, and to the walls of the box. The heating means shall be constructed to avoid stratification of temperature, and suitable means shall be provided for distributing the temperature uniformly.
3.5.2.10.2.11 The average air dry-bulb temperature in the calibrated box during Single-Packaged Dedicated System tests and calibrated box heat leakage tests shall be the average of eight temperatures measured at the corners of the box at a distance of 2 inches to 4 inches from the walls. The instruments shall be shielded from any cold or warm surfaces except that they shall not be shielded from the adjacent walls of the box. The Single-Packaged Dedicated System under test shall be mounted such that the temperature instruments are not in the direct air stream from the discharge of the Single-Packaged Dedicated System.
3.5.2.10.2.12 Calibration of the Calibrated Box. Calibration of the Calibrated Box shall occur prior to installation of the Single-Packaged Dedicated System. This shall be done either
(a) prior to cutting the opening needed to install the Single-Packaged Dedicated System, or
(b) with an insulating panel with the same thickness and thermal resistance as the box wall installed in the opening intended for the Single-Packaged Dedicated System installation. Care shall be taken to avoid thermal shorts in the location of the opening either during calibration or during subsequent installation of the Single-Packaged Dedicated System. A calibration test shall be made for air movements comparable to those expected for Single-Packaged Dedicated System capacity measurement, i.e., with air volume flow rate within 10 percent of the air volume flow rate of the Single-Packaged Dedicated System evaporator.
3.5.2.10.2.13 The heat input shall be adjusted to maintain an average box temperature not less than 25.0 °F above the test enclosure temperature.
3.5.2.10.2.14 The average dry-bulb temperature inside the calibrated box shall not vary more than 1.0 °F over the course of the calibration test.
3.5.2.10.2.15 A calibration test shall be the average of 11 consecutive hourly readings when the box has reached a steady-state temperature condition.
3.5.2.10.2.16 The box temperature shall be the average of all readings after a steady-state temperature condition has been reached.
3.5.2.10.2.17 The calibrated box has reached a steady-state temperature condition when: The average box temperature is not less than 25 °F above the test enclosure temperature. Temperature variations do not exceed 5.0 °F between temperature measuring stations. Temperatures do not vary by more than 2 °F at any one temperature- measuring station.
3.5.2.10.2.18 Data to be Measured and Recorded. Refer to Table C5 in section C6.2 of AHRI 1250–2020 for the required data that need to measured and recorded.
3.5.2.10.2.19 Refrigeration Capacity Calculation.
The heat leakage coefficient of the calibrated box is calculated by
For each Dry Rating Condition, calculate the Net Capacity:
q̇ss = Kcb (Ten−Tcb) + 3.412 × Ėc
3.5.2.10.3 Detachable single-packaged systems shall be tested as single-packaged dedicated refrigeration systems.
3.5.2.11 Variable-Capacity and Multiple-Capacity Dedicated Condensing Refrigeration Systems
3.5.2.11.1 Manufacturer-Provided Equipment Overrides
Where needed, the manufacturer must provide a means for overriding the controls of the test unit so that the compressor(s) operates at the specified speed or capacity and the indoor blower operates at the speed consistent with the compressor operating level as would occur without override.
3.5.2.11.2 Compressor Operating Levels
For variable-capacity and multiple-capacity compressor systems, the minimum capacity for testing shall be the minimum capacity that the system control would operate the compressor in normal operation. Likewise, the maximum capacity for testing shall be the maximum capacity that the system control would operate the compressor in normal operation. For variable-speed compressor systems, the intermediate speed for testing shall be the average of the minimum and maximum speeds. For digital compressor systems, the intermediate duty cycle shall be the average of the minimum and maximum duty cycles. For multiple-capacity compressor systems with three capacity levels, the intermediate operating level for testing shall be the middle capacity level. For multiple-capacity compressor systems with more than three capacity levels, the intermediate operating level for testing shall be the level whose displacement ratio is closest to the average of the maximum and minimum displacement ratios.
3.5.2.11.3 Refrigeration Systems with Digital Compressor(s)
Use the test methods described in section 3.5.2.10.1 of this appendix as the secondary method of test for refrigeration systems with digital compressor(s) with modifications as described in this section. The Test Operating tolerance for refrigerant mass flow rate and suction pressure in Table 2 of AHRI 1250–2020 shall be ignored. Temperature and pressure measurements used to calculate shall be recorded at a frequency of once per second or faster and based on average values measured over the 30-minute test period.
3.5.2.11.3.1 For Matched pair (not including single-packaged systems) and Dedicated Condensing Unit refrigeration systems, the preliminary test in sections 3.5.2.10.1.2 and 3.5.2.10.1.3 of this appendix is not required. The liquid line and suction line shall be 25 feet ± 3 inches, not including the requisite flow meters. Also, the term in the equation to calculate net capacity shall be set equal to zero.
3.5.2.11.3.2 For Dedicated Condensing Unit refrigeration systems, the primary capacity measurement method shall be balanced ambient outdoor calorimeter, outdoor air enthalpy, or outdoor room calorimeter.
[88 FR 2284928843, May 4, 2023, as amended at 88 FR 73217, Oct. 25, 2023]
