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Federal Register / Vol. 86, No. 163 / Thursday, August 26, 2021 / Notices
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refrigeration systems.15 The EER values for parallel rack systems are not expected to be representative of the compressors used in the condensing units paired with wine cellar walk-in unit coolers.
Therefore, DOE developed EER values appropriate to wine cellar walk-in cooler refrigeration systems. DOE
obtained compressor performance data from Emerson and Tecumseh product websites EERE2020BTWAV0040, No. 0002 and No. 0008, respectively for high-temperature refrigeration compressor models within the applicable capacity range 2,900 Btu/h to 36,000 Btu/h. DOE expects that the condensing units paired with wine cellar walk-in unit coolers will use either hermetic reciprocating or hermetic scroll compressors designed for use with HFC134a, R404A, or R407C refrigerants. Based on the compressor performance data, DOE
calculated representative compressor EER levels for wine cellar walk-in unit coolers using the following parameters:
38 F unit cooler exit dew point condition, as suggested by LRC LRC
Coil, No. 1 at pp. 3.
2 F equivalent suction line dew point pressure drop, consistent with AHRI 12502009 section 7.9.1.
7 F evaporator exit superheat, rounding to whole number values of the 6.5 F superheat test condition prescribed in the footnote to Table 15 of Appendix C in case a value is not provided in an installation manual.
55 F refrigerant temperature entering the compressor, representing a 10 F refrigerant vapor temperature rise in the suction line, consistent with the temperature rise implied for mediumtemperature refrigeration system test conditions.16
90 F annual average condensing temperature. This assumes that the condensing unit serving the unit cooler would be located outdoors and that head pressure control would prevent excessively cold condensing operation at cold outdoor temperatures.17
15 See for example, Hussmann Parallel Rack Systems, www.hussmann.com/ns/TechnicalDocuments/0427598_D_Rack_IO_EN.pdf.
16 AHRI 12502009 Table 11 prescribes a return gas temperature measured at the condensing unit inlet location equal to 41 F for testing medium temperature condensing units. Also, Table 15 and Section 3.3.1 of Appendix C prescribe testing medium-temperature unit coolers using 25 F
saturated suction temperature this is the same as unit cooler exit dew point temperature, and 6.5 F
superheat in case the installation manual doesnt provide superheat requirements. Thus, the unit cooler exit temperature would be 25 F + 6.5 F =
31.5 F, and the implied suction line temperature rise is 41 F31.5 F = 9.5 F. The analysis conducted for wine cellars rounds this to 10 F.
17 Head pressure control refers to reduction of condenser heat transfer performance using fan
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DOE plotted the calculated compressor EER values versus calculated unit cooler capacity and noted that the EER can significantly vary with capacity EERE2020BT
WAV0040, No. 0009. EER is generally low for low-capacity compressors and high for high-capacity compressors, with a transition region in between.
Based on the plotted calculations, DOE
determined for the purpose of the interim waiver that a representative value for EER should depend on capacity. As such, DOE developed different functions of EER for three distinct capacity ranges. Table 1
summarizes these capacity ranges and EER functions for high-temperature compressors.

TABLE 1EER VALUES FOR HIGH
TEMPERATURE COMPRESSORS AS A
FUNCTION OF CAPACITY FOR WINE
CELLAR WALK-IN COOLER REFRIGERATION SYSTEMS
Capacity Btu/hr
EER
Btu/Wh <10,000
10,00019,999 ..
20,00036,000 ..

11.
0.0007 Capacity + 4.
18.

Section 3.3.7 of Appendix C specifies section 7.9 of AHRI 12502009 for calculation of AWEF and net capacity for unit coolers tested alone. The alternate test procedure required under this interim waiver modifies section 3.3.7 of Appendix C to use the EER
values provided in Table 1 for determining AWEF.
The alternate test procedure required under the interim waiver also includes the following modifications to LRC
Coils suggested approach: For systems that can be installed with ducted evaporator air or without ducted evaporator air, testing would be conducted at 50 percent of the maximum ESP, consistent with the AHRI August 2020 Letter recommendations, subject to a tolerance of 0.00/+0.05 in. wc.18 DOE
understands that maximum ESP is generally not published in available cycling or other means when it is cold outside in order to avoid unusually low condensing temperature. Such low condensing temperatures are undesirable because they can reduce refrigeration system performance and/or increase risk of compressor damage. A typical minimum condensing temperature is 70 F, which may apply whenever outdoor temperature is lower than 50 F.
DOE selected the 90 F annual average to be representative of operation that would involve condensing temperature ranging from 70 F to 120
F, since outdoor temperature varies.
18 Inches of water column in. wc is a unit of pressure conventionally used for measurement of pressure differentials.

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literature such as installation instructions, but manufacturers do generally specify the size and maximum length of ductwork that is acceptable for any given unit in such literature. The duct specifications determine the ESP
that the unit would experience in the field.19 The provision of allowable duct dimensions is more convenient for installers than maximum ESP, since it relieves the installer from having to perform duct pressure drop calculations to determine ESP. DOE independently calculated the maximum pressure drop over a range of common duct roughness values 20 using duct lengths and diameters published in LRC Coils installation manuals.21 DOEs calculations show reasonable agreement with the maximum ESP values provided by LRC Coil for the specified basic models. Given that the number and degree of duct bends and duct type will vary by installation, DOE found the maximum ESP values provided by LRC
Coil to be sufficiently representative.
Selection of a representative ESP
equal to half the maximum ESP is based on the expectation that most installations will require less than the maximum allowable duct length. In the absence of field data, DOE expects that a range of duct lengths from the minimal length to the maximum allowable length would be used; thus, DOE believes that half of the maximum ESP would be representative of most installations. For unit cooler basic models that are not designed for the ducting of air, this design characteristic must be clearly stated.
Additionally, if there are multiple evaporator fan speed settings, the speed setting in the units installation instructions would be used for testing.
However, if the installation instructions do not specify a fan speed setting for ducted installation, systems that can be installed with ducts would be tested with the highest available fan speed.
The ESP would be set for testing by 19 The duct material, length, diameter, shape, and configuration are used to calculate the ESP
generated in the duct, along with the temperature and flow rate of the air passing through the duct.
The conditions during normal operation that result in a maximum ESP are used to calculate the reported maximum ESP values, which are dependent on individual unit design and represent manufacturer-recommended installation and use.
20 Calculations were conducted over an absolute roughness range of 1.04.6 mm for flexible duct as defined in pages 12 of an OSTI Journal Article on pressure loss in flexible HVAC ducts at www.osti.gov/servlets/purl/836654 Docket No.
EERE2020BTWAV00400006 and available at www.regulations.gov.
21 Duct lengths and diameters can be found in LRC Coils installation manuals at www.regulations.gov Docket No. EERE2020BT
WAV00400005, and EERE2020BTWAV
00400004.

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