Sizing a Heat Pump For Negative-Degree Temperatures
Should a heat pump be sized based on its reduced output at low temperatures? Building a house where the design temp in winter is -5F. Will be a ranch home with a walkout basement and currently looking at a separate ducted heat pump for each level like Mitsubishi SUZ+SVZ. Likely going to add electric resistance backup heat to the air handlers as it certainly gets colder than that sometimes.
These units have about 80% capacity at -15F, not sure what it is at -5F. Is the correct option to size them with the understanding that at -5F they will have reduced capacity, maybe something like 90% and then worry about resistance heat after that? Or would I be better off ignoring that and expect to need resistance heat use at anything below 5F?
GBA Detail Library
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