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Federal Register / Vol. 86, No. 58 / Monday, March 29, 2021 / Rules and Regulations
1. Methodology In the June 2020 NOPR, DOE
proposed a test method to measure the efficiency gains for variable-speed room ACs that are not captured by the previous DOE test procedure. 85 FR
35700, 3570835709 Jun. 11, 2020.
DOE based the proposed method on the alternate test procedure required under the LG Waiver and the Midea Waiver, collectively, the waivers for specified basic models of variable-speed room ACs. 84 FR 20111 May 8, 2019
and 85 FR 31481 May 26, 2020. The alternate test procedure proposed in the NOPR, which is substantively consistent with the waivers, is generally consistent with the approach in AHAM RAC1
2020, as discussed in section III.B.1 of this document. As discussed in this section below, DOE is adopting the AHAM RAC12020 test procedure in this final rule, with some modifications for the purposes of improved representativeness and repeatability, which provides a methodology for obtaining a reported CEER value by adjusting the intermediate CEER value as tested at the 95 F test condition according to appendix F using a performance adjustment factor PAF.
Conceptually, the approach for variable-speed room ACs adopted in this final rule involves measuring performance over a range of four test conditions, applying user settings to achieve the full compressor speed at two test conditions and manufacturerprovided instructions to achieve a reduced fixed compressor speed at the other two test conditions, which collectively comprise representative use. These temperature conditions were derived from the DOE test procedure for central air conditioners with variablespeed compressors and include three reduced-temperature test conditions under which variable-speed room ACs perform more efficiently than singlespeed room ACsand the test condition specified in the previous test procedure.17 The single-speed room AC
test procedure, however, does not factor in the reduced-temperature test conditions under which single-speed units also will perform more efficiently although not as well as variable-speed room ACs. As a result, comparing variable-speed performance at all test conditions against a single-speed unit at the highest-temperature test condition would not yield a fair comparison. The 17 The central air conditioner test procedure can be found at Title 10 of the CFR part 430, subpart B, appendix M, Uniform Test Method for Measuring the Energy Consumption of Central Air Conditioners and Heat Pumps.

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PAF represents the average relative benefit of variable-speed over singlespeed across the whole range of test conditions. It is applied to the measured variable-speed room AC performance only at the high-temperature test condition to provide a comparison to the single-speed CEER metric based on representative use.
The steps for determining a variablespeed room ACs PAF are summarized as follows:
Measure the capacity and energy consumption of the sample unit at the single test condition used for singlespeed room ACs 95 F dry-bulb outdoor temperature, with the compressor speed at the maximum full speed, achieved using the user settings i.e., setpoint selected in accordance with the appendix F test.
Measure the capacity and energy consumption of the sample unit at three additional test conditions 92 F, 87 F, and 82 F dry-bulb outdoor temperature,18 with compressor speed at full using the user settings in accordance with appendix F, and fixed at intermediate and minimum low speed, respectively.19 Using theoretically determined adjustment factors,20 calculate the equivalent performance of a single-speed room AC
with the same cooling capacity and electrical power input at the 95 F drybulb outdoor temperature, with no cycling losses i.e., a theoretical comparable single-speed room AC for each of the three test conditions.
Calculate the annual energy consumption in cooling mode at each of the four cooling mode test conditions for a variable-speed room AC, as well as for a theoretical comparable singlespeed room AC with no cycling losses.
This theoretical single-speed room AC
would perform the same as the variablespeed test unit at the 95 F test condition but perform differently at the other test conditions.
Calculate an individual CEER value at each of the four cooling mode test conditions for the variable-speed room AC, as well as for a theoretical comparable single-speed room AC with no cycling losses.
Using cycling loss factors derived from an industry test procedure and DOE test data,21 calculate an adjusted 18 The additional reduced-temperature conditions are described further in section III.C.2 of this document.
19 The fixed compressor speeds are described further in section III.C.3 of this document.
20 These adjustment factors are described further in section III.C.4 of this document.
21 The derivation of these cycling loss factors is described in more detail in section III.C.5 of this document.

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CEER value at each of the four cooling mode test conditions for a theoretical comparable single-speed room AC, which includes cycling losses.
Using weighting factors 22
representing the fraction of time spent and cooling load expected at each test condition in representative real-world operation, calculate a weighted-average CEER value reflecting the weightedaverage performance across the four test conditions for the variable-speed room AC, as well as for a theoretical comparable single-speed room AC.
Using these weighted-average CEER
values for the variable-speed room AC
and a theoretical comparable singlespeed room AC, calculate the PAF as the percent improvement of the weightedaverage CEER value of the variablespeed room AC compared to a theoretical comparable single-speed room AC.23 This PAF represents the improvement resulting from the implementation of a variable-speed compressor.
DOEs approach to addressing the performance improvements associated with variable-speed room ACs is generally consistent with the alternate test procedures required in the waivers and with the test procedure updates proposed in the June 2020 NOPR.24 The following sections of this document describe each aspect of the approach in greater detail.
2. Test Conditions As discussed previously, variablespeed room ACs provide improved performance at reduced cooling loads by reducing the compressor speed to match the load, thereby improving system efficiency. DOE recognizes that throughout the cooling season, room ACs operate under various outdoor temperature conditions. DOE also asserts that these varying outdoor conditions present a range of reduced cooling loads in the conditioned space, under which a variable-speed room AC
would perform more efficiently than a 22 These fractional temperature bin weighting factors are described in more detail in section III.C.6
of this document.
23 The performance adjustment factor is described in more detail in section III.C.7 of this document.
24 DOE estimates that the CEER value for a variable-speed room AC determined in accordance with the amendments adopted in this final rule would be about 1.6 percent greater than the CEER
value determined in accordance with the June 2020
NOPR proposed test approach, which was consistent with the alternate test procedure prescribed in a Decision and Order granting a waiver from the DOE test procedure for room air conditions to LG Electronics 84 FR 2011; May 8, 2019 and in an Interim Waiver granted to GD
Midea Air Conditioning Equipment Co. LTD 84 FR
68159; Dec. 13, 2109. 85 FR 35700, 35709.

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