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Federal Register / Vol. 86, No. 115 / Thursday, June 17, 2021 / Proposed Rules
as a refrigeration system used to cool the interior of a walk-in cooler or a walk-in freezer operating above 10 F.
Alternatively, another approach would allow medium-temperature refrigeration systems used in hightemperature freezer walk-in applications to be tested and certified at their lowest application temperature conditions.
This approach would be similar to that taken for commercial refrigerators, freezers, and refrigerator-freezers, for which manufacturers report the lowest application product temperature, i.e. the lowest average compartment temperature at which the equipment is capable of operating during testing section 2.2 of appendix B to 10 CFR
part 431 subpart C. For walk-ins, this concept could be based on the lowest evaporator return air temperature for matched-pair refrigeration systems and the lowest saturated suction temperature and a suitable corresponding return gas temperature for condensing units tested separately.
This approach would result in ratings for the units in high-temperature freezer applications that are directly representative of field performance, as the refrigeration system would be tested at a representative box temperature for such an application. Further, this approach would not presuppose what the optimal high-temperature freezer operating condition would be, i.e., it avoids selecting a standardized condition that may be unachievable by some units. However, AWEF ratings obtained from the lowest application temperature for different units, which would be rated for different box temperatures, would not be directly comparable. The approach would also add testing and reporting burden associated with the additional test condition.
DOE is also considering a third approach that would establish a single standardized test condition at which high-temperature freezer refrigeration equipment would be tested. This approach would result in AWEF ratings that are slightly less representative of field performance than the lowest application temperature approach, while still creating the potential need to establish a new equipment class or classes for low-temperature refrigeration systems. However, under a standardized test condition approach, all high-temperature freezer refrigeration systems would be rated at the same condition, providing directly comparable ratings for models that serve similar applications.
DOE is investigating if and how the calculations used for determining the AWEF of WICF condensing units tested
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alone and with matched systems would need to be modified for products certified with the latter two approaches discussed previouslyfor example, whether any potential changes to the specified duty cycle at 95 F ambient temperature for an outdoor system would be necessary.
Issue 43: DOE requests feedback on the three approaches discussed in this section to address high-temperature freezer walk-ins, as well as any other potential approaches not raised in this RFI.
Issue 44: DOE also requests information that would help inform the development of test procedures for hightemperature freezer refrigeration systems, should such an approach be necessary. Additionally, DOE requests whether there are specific characteristics that distinguish a hightemperature freezer refrigeration system from a medium-temperature refrigeration system, in order to better define this category of equipment.
Issue 45: DOE also requests comment on whether 10 F is the appropriate lowest end of the application range for equipment used in walk-in hightemperature freezers that cannot be tested using the 10 F freezer test condition. Furthermore, DOE requests comment on whether all mediumtemperature systems matched-pair, condensing unit, evaporator can be operated and tested at 10 F or equivalent refrigerant suction conditions, or whether there is a wide range at the low-end of the operating range that depends on the design of the system.
Issue 46: Regarding the testing of a medium-temperature refrigeration system in the high-temperature freezer range, DOE requests information on what specified test procedure parameters would need to be altered and how in order for the test to be representative of field operation. In answering, DOE requests that commenters provide the supporting reasons for any suggested recommendations. DOE requests information on whether a single standardized high-temperature freezer room condition could be appropriate for testing this group of walk-ins, and if so, what such an appropriate temperature would be.
Issue 47: Finally, DOE requests comment on what, if any, changes would be needed in the calculation of AWEF for high-temperature freezer operation, and why.
If DOE were to pursue the lowest application temperature approach or the standardized high-temperature freezer test condition approach, DOE would
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need to establish certain new default values to calculate the AWEF and net capacity of stand-alone hightemperature freezer dedicated condensing units. Currently, the test procedure provides equations for determining evaporator fan power, defrost energy, and defrost heat load, all of which are used in lieu of matched unit cooler test data section 3.4.2 of Appendix C.
The current test procedure offers two separate equations that relate the cooling capacity to the evaporator fan power for mediumand lowtemperature unit coolers section 3.4.2.2
of Appendix C. Based on the condensing unit capacity at the medium temperature test condition 35 F box temperature, using the mediumtemperature equation seems to be the most appropriate approach since the condensing units in question would also be certified as medium-temperature condensing units. This approach also assumes that fan energy use at hightemperature freezer conditions will be the same as fan energy use at mediumtemperature conditions, since it makes no adjustment in the calculated fan power for the high-temperature freezer application.
Issue 48: DOE requests comment on the appropriateness of using the current medium-temperature refrigeration system default fan input power equation found at section 3.4.2.2 of Appendix C
to represent the fan input power of hightemperature freezer refrigeration systems. If the current mediumtemperature refrigeration system default fan input power equation is not representative of the fan input power for high-temperature freezer refrigeration systems, DOE requests suggestions for a more appropriate equation, or alternative relationships to consider, as well as any relevant data.
In the current test procedure, defrost energy and defrost heat load for standalone dedicated condensing units are estimated based on the condenser capacity using an equation in section 3.4.2 of Appendix C. The calculations apply only to freezer models, since they assume that refrigeration systems serving walk-in coolers are not equipped for defrost capability and thus have no defrost energy or heat load.
However, medium-temperature refrigeration systems designed for hightemperature freezer applications require defrost capability because frost that collects on the evaporator during the compressor off-cycle will not melt in the sub-freezing walk-in temperature conditions. The energy and heat load of these high-temperature freezer defrost systems may differ significantly from
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