Why should I worry about my heat strips?
Air-source heat pumps contain two separate heating systems: the heat pump and heat strips. Heat strips are electric resistance heating coils located inside the indoor air handler, the portion of the system which circulates the indoor air. They look much like the coils inside a kitchen toaster. The heat pump is energy efficient and will heat the home at little expense. The heat strips, however, will consume about three times as much energy as a heat pump while producing the same amount of heat.
What do I need to know about my heat pump and heat strips?
Heat pumps gather heat from either air, water or the ground and are respectively called air-source, water-source, or ground-source heat pumps. Nearly all heat pumps in the Georgia area are the air-source type. If your heat pump has an outdoor compressor unit, which draws in and expels outdoor air during heating, it is an air-source heat pump.
The heat strips are energized during three different operational modes. But, they are truly needed only during the de-icing and the auxiliary heating modes.
1. De-icing—Also called defrost cycle. During winter the evaporator coil in the outdoor compressor unit becomes colder than the outside air, so water often condenses on it and freezes. To remove this ice the heat pump automatically switches for several minutes to the air conditioning mode, which raises the temperature of the frozen coil, melting the ice. During this brief period, heat strips are energized to keep the system from cooling the home.
2. Auxiliary Heat—Also called supplemental or back-up heat. When outdoor temperatures drop below approximately 40 degrees, a properly-sized heat pump is not able to
furnish all the heat the house needs. So, strip heat is provided to assist or supplement the heat pump while the heat pump is still running.
3. Emergency Heat—The third mode is called emergency heat. It can be activated by using a manual slide switch located on the indoor thermostat. The strip heat mode is used when the heat pump compressor has failed. It turns off the heat pump to prevent further damage and turns on the heat strips to continue heating the house.
What are my options for managing my heat strips?
The best and least expensive option for controlling strip heat usage is limiting frequent thermostat adjustments. This is a wasteful practice because the indoor thermostat is very sensitive to very slight adjustments. If the setting is moved just a few degrees upward, the strip heat may be engaged and begin to consume electricity at a rate three times greater than that of the heat pump alone.
Three possible control measures to consider are to:
1. Install a toggle switch within the strip heat control wire so that it can only be activated manually.
2. Install a programmable thermostat that has a “ramped recovery” feature that determines the amount of time the heat pump needs to gradually reach a desired temperature.
3. Install an outdoor thermostat within the compressor unit that prevents strip heat from coming on above a pre-determined outdoor temperature.
How much can I save by managing my heat strips?
The heat strips are rated by the electricity they consume. Ten kilowatts (kW) is a normal size heat strip for the average home in Monroe. The cost of one kilowatt-hour (kWh) of electricity is $0.10. At this price, the 10 kW heat strip will cost $1.00 every hour it is in operation. If you are able to reduce your heat strip usage by 50 percent—from 60 hours per month to 30 hours per month—you would save about $30.