Auxiliary Heat Pumps

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A residential heat pump heats a home with an energy efficient refrigeration system that moves heat from outdoors. Unfortunately, a heat pump’s refrigeration compressor can’t produce enough heat when the outdoor temperature drops into the 30s, so the heat pump needs less efficient auxiliary resistance heat.The heat, produced by these same electric resistance coils, is called emergency heat if the compressor fails. In this mode, the electric coils have to heat your home by themselves.

Auxiliary heat is far less efficient than using the heat pump’s compressor. So it’s good practice to adjust your heat pump to avoid using auxiliary heat until the weather gets very cold. To accomplish this, all heat pumps should have an outdoor thermostat that won’t allow the auxiliary heat to come on until the outdoor temperature is 40° F or below. Ask your service technician if your heat pump is equipped with an outdoor thermostat, and have one installed if needed.

The way you operate your indoor thermostat is also very important. There are two practices you want to avoid. The first is raising the thermostat to a higher-than-needed setting in an attempt to bring the temperature up from night setback or other temperature reduction faster. When you return home, just set your thermostat to the temperature you’d like your home to be, and let the system do the rest. The other practice to avoid is setting the thermostat to emergency heat. Both of these practices will bring on the inefficient auxiliary heat and increase your electrical consumption.

See The Homeowners Handbook to Energy Efficiency orResidential Energy: Cost Savings and Comfort for Existing BuildingsChapter 6 for more information. For professional information about heating systems and energy efficiency see Saturn Hydronic Systems Field Guide.