How Are Prototype Cooling Coil Efficiencies Determined?
Working with the latest DOE prototype for stand alone retail, I find the following COPs listed for the cooling coils:
PSZ-AC:1 --> 3.80
PSZ-AC:2 --> 3.40
PSZ-AC:3 --> 4.12
PSZ-AC:4 --> 4.12
These seem to all exceed the minimum efficiency listed in ASHRAE 90.1-2019 for single packaged air cooled air conditioners, of any size. Of course this comparison requires some awkward conversions (SEER or IEER to COP) but these COPs don't even seem close the the EERs specified for units above 65k btu/hr.
Based on the specified EERs only, the minimum efficiencies range from a COP of 2.784 for units over 760k btu/hr up to 3.22 for units between 65k and 135k (smaller units only specify a SEER 14, which i calculate as 3.45, roughly).
What am i missing? do the numbers in 90.1 include fan energy that has to be removed from the coil COP in EPlus?
and, while were talking about prototypes and efficiency determinations, if a model has one large zone served by 1 HVAC unit where in real life that 1 zone would most likely be served by a few smaller units, does the prototype use the minimum efficiency appropriate for the unit sized to serve the entire zone or for some assumed number of smaller units that add up to the modelled capacity?
Thanks.
