Quote:
Originally Posted by Biggd
In NH lakes region I think you would still need another heat source for those extreme cold spells. I know some of the Hyper units say the will work to -15 but what happens if you find out it won't keep up and you have no other heat source?
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It's a matter of conditions for which the unit is sized. Even though an air source heat pump may be designed to deliver a certain amount of heat at some design minimum outside air temperature, and may well deliver significant but reduced heat output below that temperature, the heat demand of the house is greater as the temperature drops. So the choice is either selecting a unit with capacity for the minimum outside temperature you likely will see or selecting it to deliver adequate heat most of the time but providing something (like electric resistance heating or woodstove) to make up the difference for the extremes. In either case, a really good heat loss calculation must be done for the particular house. Rules of thumb don't cut it. Installers of fired heating systems (oil or propane) usually don't do any such calculation, as the units installed are nearly always far oversized.