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Federal Register / Vol. 86, No. 58 / Monday, March 29, 2021 / Rules and Regulations AC that cannot operate at precisely 57
percent of the full-load cooling capacity cannot exactly match the cooling load at the 82 F test condition, it could compensate for this in real world operation at an 82 F outdoor temperature by operating at a lower compressor speed and moving to a higher compressor speed if the room becomes too hot. DOE observed variable-speed compressors with this behavior during load-based testing, though noted that the compressor speed adjustments did not occur frequently, resulting in extended periods of operation at a single compressor speed.
Furthermore, the difference in power consumption between the two speeds observed in these scenarios was only about 5% of the full load operating power, and therefore this style of operation would still result in more efficient operation compared to cycling a single-speed compressor on and off to maintain the reduced load. These variable-speed units still provide significant energy savings, so it is important to account for this sort of variable-speed compressor behavior and ensure the test procedure is applicable to even those variable-speed room ACs that have discrete compressor speed steps that may not provide exactly 57
percent of the full-load cooling capacity.
DOE further notes that requiring a low compressor speed that results in a single loading percentage i.e., 57 percent of the full-load cooling capacity with no tolerance could greatly increase design and manufacturing burden, and thus may disincentivize the adoption of more efficient technology being newly introduced for room ACs. A 10-percent range would allow for the various types of variable-speed compressors i.e., discrete and non-discrete, avoid significant burden on manufacturers, and avoid disincentivizing the adoption of this technology. An upper compressor speed limit of 57 percent of the full-load cooling capacity would ensure that the unit does not cycle on and off under the cooling load expected at an outdoor temperature of 82 F, which would negate much of the efficiency benefits relative to singlespeed room ACs. Therefore, DOE
proposed a lower limit of 47 percent to maintain the desired 10-percent range of cooling loads while setting 57 percent of the full-load cooling capacity as the upper limit.
In this final rule, DOE is revising the definition of full compressor speed proposed in the June 2020 NOPR, to account for the new requirements discussed in section III.C.3.a i.e., to require that user settings be
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implemented to achieve maximum cooling capacity when testing using full compressor speed, rather than fixing the compressor speed using instructions provided by the manufacturer.
Furthermore, DOE is also revising the intermediate compressor speed definition proposed in the June 2020
NOPR, to clarify that the intermediate compressor speed is defined based on the measured capacity at the 95 F and 82 F test condition, using the full and low compressor speeds, respectively.
Thus, DOE is adopting its proposals from the June 2020 NOPR, as detailed below.
In summary, DOE defines the following in newly added Sections 2.14, 2.15, and 2.16 of appendix F:
Full compressor speed full means the compressor speed at which the unit operates at full load test conditions, achieved by using user settings to achieve maximum cooling capacity, according to the instructions in ANSI/
ASHRAE Standard 162016 Section 6.1.1.4.
Intermediate compressor speed intermediate means a compressor speed higher than the low compressor speed at which the measured capacity is higher than the capacity at low compressor speed by one third of the difference between Capacity4, the measured cooling capacity at test condition 4 in Table 1 of this appendix, and Capacity1, the measured cooling capacity with the full compressor speed at test condition 1 in Table 1 of this appendix, with a tolerance of plus 5
percent designs with non-discrete speed stages or the next highest inverter frequency step designs with discrete speed steps, achieved by following the instructions certified by the manufacturer.
Low compressor speed low as the compressor speed specified by the manufacturer at which the unit operates at low load test conditions, such that Capacity4, the measured cooling capacity at test condition 4 in Table 1
of this appendix, is no less than 47
percent and no greater than 57 percent of Capacity1, the measured cooling capacity with the full compressor speed test condition 1 in Table 1 of this appendix.
E. Active Mode Testing The following sections describe amendments and other considerations regarding the active mode testing provisions of appendix F.
1. Cooling Mode The DOE room AC test procedure uses a calorimeter test method to determine the cooling capacity and associated
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electrical power input of a room AC. See Sections 3.1 and 4.1 of appendix F, as amended. Under this approach, the test unit is installed between two chambers, one representing the indoor side and the other representing the outdoor side, which are both maintained at constant conditions by reconditioning equipment. The room AC operates in cooling mode, transferring heat from the indoor side to the outdoor side, while the reconditioning equipment counteracts the effects of the room AC
to maintain constant test chamber conditions. The room AC cooling capacity is determined by measuring the required energy inputs to the reconditioning equipment.
a. Test Setup and Air Sampling In the June 2020 NOPR, DOE
discussed concerns about whether the measured calorimeter chamber temperature reading is representative of conditions at the test unit condenser and evaporator inlet, which may be affected by recirculation from the condenser and evaporator exhaust, respectively, thereby potentially reducing test repeatability and reproducibility. 85 FR 35700, 35715
Jun. 11, 2020. DOE noted that the size, capability, and orientation of components within calorimeter test chambers may vary significantly, and that third-party laboratories extensively analyze their chambers and testing apparatus to maintain consistent and accurate air sampling measurements.
DOE also understood that temperature gradients and unique airflow patterns can result from the interaction of a chamber reconditioning apparatus and the room AC under test, and that these interactions are particular to and dependent upon factors such as chamber size and shape, chamber equipment arrangement, size of reconditioning apparatus, and others, as noted in ANSI/ASHRAE Standard 16
2016 Section 8.2.7. Therefore, in the June 2020 NOPR, DOE contended that universal requirements for air sampling instrumentation and thermocouple placement could potentially reduce test accuracy and reproducibility. As discussed in section III.B.2 of this document, DOE proposed to update the reference to ANSI/ASHRAE Standard 16
to the most current 2016 version, which includes additional clarification on best practices for air sampler and thermocouple placement. Id.
DOE received no comments on the test setup and air sampling discussion and proposals from the June 2020
NOPR. For the reasons discussed in the preceding paragraph, DOE is updating the reference to ANSI/ASHRAE

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