Heat pumps must be sized and installed properly to work efficiently. Heat pumps are sized for either the heating demand or cooling demand, depending on which implies the larger unit (almost always cooling). However, heat pumps do not perform well over extended periods of sub-freezing temperature and it may not be cost effective to meet all your heating needs with an air-source heat pump.
Ground source heat pumps (GSHPs) are more efficient and less noisy than conventional air-source heat pumps. Though GSHPs are more expensive to install, the dramatic improvement in efficiency can yield attractive life cycle cost savings. However, the appropriatenes of a GSHP depends on the size of your lot, the conditions of the subsoil and landscape, and sometimes the relative magnitudes of summer cooling and winter heating requirements.
Select a heat pump with a higher HSPF. For units with comparable HSPF ratings, check their steady-state rating at -8.3°C, the low temperature setting. The unit with the higher rating will be more efficient.
Select a heat pump with a demand-defrost control. This will minimize the defrost cycles thereby reducing supplementary and heat pump energy use.
Select a heat pump with an outdoor sound rating of 7.6 bels or lower. The lower the value, the less noisy the outdoor unit.
If installing a heat pump in an existing home without an existing heat pump or air conditioner, ductwork may need to be enlarged. Heat pump systems generally require larger duct sizes than other central heating systems. For proper heat pump operation, air flow should be 50 to 60 liters per second per kilowatt-hour or 400 to 500 cubic foot per minute per ton of cooling capacity.
If a heat pump is added to an electric furnace, the heat pump coil can usually be placed on the cold (upstream) side of the furnace for greatest efficiency.
Fans and compressors make noise. Locate the outdoor unit away from windows and adjacent buildings. Some units also make noise when they vibrate. You can reduce this noise by selecting quiet equipment or by mounting the unit on a noise-absorbing base.
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