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Federal Register / Vol. 86, No. 58 / Monday, March 29, 2021 / Rules and Regulations load-tested room AC unit could be as high as 0.42, based on the 21-percent performance loss observed at 50-percent load; this compared with the 12.5percent loss assumed at 50-percent load with the default Cd assumption. Rice, No. 17 at pp. 34 The California IOUs and Rice recommended DOE conduct additional investigative load-based testing on single-speed room ACs to better estimate the Cd at the 82 F test condition. California IOUs, Public Meeting Transcript, No. 12 at p. 30;
Rice, No. 17 at pp. 34
Rice also commented that a room AC
unit is unlikely to be sized exactly to match the room load at 95 F outdoor ambient conditions. Rice further commented that a minimal 10-percent oversizing, equivalent to that assumed in AHRI Standard 210/240 for unitary ACs, would be more appropriate and would also provide a common basis with current AC ratings practice. Rice stated that use of 110-percent sizing would also provide an appropriate performance benefit, estimated to be approximately 3 percent, to variablespeed room ACs relative to single-speed units. Accordingly, Rice recommended that the assumption of exact sizing be modified to at least be consistent with 110-percent sizing as assumed in AHRI
Standard 210/240 for unitary air conditioners. With 110-percent sizing, Rice noted that the default CLFs at 95, 87, and 82 F would need to be adjusted to 0.977, 0904, and 0.864, respectively, for a Cd of 0.25. Rice also noted that they would need further adjustment if a different default Cd were selected or if the slope of the default single-speed capacity curve was changed. As for the proposed 75 F test point, Rice commented that the CLFs with a 0.25
Cd are 0.820 at 100-percent sizing and 0.813 at 110-percent sizing. Rice, No.
19 at p. 6; see also Rice, Preliminary Analysis, No. 25 at pp. 12
DOE disagrees with Rices claim that it is unlikely that room ACs are sized to match room cooling load at a 95 F
outdoor temperature test condition.

Room ACs are intended to cool a single room, where the cooling load is more likely to remain steady or within a smaller range. DOE is not aware of any data showing that room ACs are typically oversized. Given the application of room ACs to a more limited space, DOE has determined that it is reasonable to assume that room ACs are sized to match room cooling loads at a 95 F outdoor temperature test condition.
DOE acknowledges the concerns regarding the Cd as proposed in the June 2020 NOPR. In response, DOE
conducted additional testing in support of this final rule to determine whether the AHRI Standard 210/240 single-stage Cd of 0.2 suggested by AHAM or a higher value such as 0.42 as suggested by the California IOUs, NEAA, and Rice would be more appropriate. DOE
conducted load-based testing on two single-speed room ACs with cooling capacities comparable to variable-speed room ACs of the same brand/
manufacturer currently on the market using an outdoor temperature of 82 F
and cooling loads between 47 and 57
percent of the full load, with a target of 52 percent i.e., the center of the acceptable range specified in the low compressor speed definition. DOE did not consider cycling losses at an outdoor temperature of 75 F, based on the decision to not include testing at that temperature condition, as discussed in section III.C.2 of this document. The results of this testing are summarized in Table III5.

TABLE III5CYCLING LOSS FACTORS
Load %

Unit Unit 1
Unit 2

52
49
54
52

Cd
16459

On average, the two single-speed room ACs had a Cd of 0.38 at the 82 F
test condition and 52 percent cooling load, which is relatively close to the maximum Cd value of 0.42 suggested by Rice. Based on DOEs test data, use of a Cd of 0.38 would increase a variablespeed room ACs measured CEER by approximately 5.5 percent. Based on this testing, DOE is adopting a Cd of 0.38, resulting in a CLF at the 82 F test condition of 0.81. Interpolating between the 82 F test condition and CLF of 0.81
and 95 F test condition and CLF of 1, results in a CLF of 0.883 for the 87 F
test condition and a CLF of 0.956 for the 92 F test condition.
6. Test Condition Weighting Factors In the approach proposed in the June 2020 NOPR, the four interim CEER
values representing each of the four cooling mode test conditions were combined, using four weighting factors, into a single weighted-average CEER
value. 85 FR 35700, 3571135712 Jun.
11, 2020. The resulting weightedaverage CEER value represented the weighted-average performance across the range of outdoor test conditions. Id.
DOE calculated weighting factors based on the fractional temperature bin hours in Table 19 of DOEs test procedure for central air conditioners at appendix M.
DOE identified the fractional temperature bin hours representing the four test conditions in the proposed approach and normalized these four values from appendix M so that they sum to 1.00.
Table III6 shows the June 2020
NOPR weighting factors for each of the four test conditions.

0.42
0.39
0.30
0.34

Due to difficulties in achieving the target load percentage of 52% for Unit 2, data for the nearest higher and lower data points were interpolated to estimate the expected Cd at a 52% load.

TABLE III6JUNE 2020 NOPR PROPOSED TEMPERATURE CONDITION WEIGHTING FACTORS
Evaporator inlet air, F

Test condition
Dry bulb Test Test Test Test
Condition Condition Condition Condition
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2 3
4

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Wet bulb 80
80
80
80

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Condenser inlet air, F

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67
67
67

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92
87
82

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75
72.5
69
65

CEER
weighting factor 0.05
0.16
0.31
0.48