Due to the recent cold, polar vortex weather, I have received several questions concerning heat pumps. It seems the readers’ homes are cooler than normal and the outside unit of the heat pump/air conditioner runs continuously. The basic question is why is the house is so cold and is there anything they can do about it?
A heat pump is similar to an air conditioner, but runs in reverse in the winter. In summer the outside condensing coil releases heat that was absorbed at the interior evaporator coil.
In the winter there is a reversing valve incorporated into the outside unit that reverses the flow of the refrigerant, allowing latent heat to be brought in from the outside air.
When the outside temperature falls below about 20 degrees, the heat pump is less efficient. There is almost no latent heat for the heat pump to use when it’s really cold outside. This is when you’ll have to manually turn the furnace on.
Homes with a heat pump will have a backup system to heat the home with either electricity or fossil fuels. When the home’s thermostat is set to heat and the heat pump is running in extremely cold weather, you are wasting the energy it takes to run the heat pump. It will not heat the home in extremely cold weather.
The thermostat should have a switch for “Heat.” The same switch can be adjusted to “Supplemental,” “Emergency” or “Auxiliary” heat. The purpose is to eliminate the heat pump and to turn the furnace on.
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