Did you know that heat pumps are air conditioning units that work backwards? Just as air conditioning units, heat pumps remove heat from your home in summer months and expel it outside. However, when your house needs to be warmed up as the seasons change, heat pumps reverse their function and become heaters. They absorb heat from outdoors and bring it into your house for heating.
If you have spent any time at your heat pump’s thermostat, you will notice an indicator for auxiliary heat. Usually the light is just a signal that the back-up electric coils in your air handler are energized. There are two completely normal situations when this happens.
First, heat pumps build up ice on outdoor coils. If the ice disrupts the refrigerant cycle, the heat pump will enter defrost mode. In defrost mode, the system switches to air conditioning mode for a short period of time to melt the ice on the outdoor coil. During this time, the heat pump cannot heat the home, and the auxiliary heat fills in.
Second, there may be times when the temperature in the house is more than 2 degrees below the thermostat heat setting. If you just raised the set temperature, the back-up heat will come on until the room temperature reaches the thermostat request. This is completely normal. If you haven’t changed the set temperature, the auxiliary heat is kicking in because the heat pump cannot achieve the set temperature. If the outdoor temperature is very cold, the auxiliary heat is assisting the heat pump, which is normal. The colder the outside temperature, the more often you will see the auxiliary heat light come on because the heat pump cannot produce enough heat by itself to maintain the indoor temperature.
Please be aware that if your heat pump unit is running in auxiliary heat mode when the outside temperatures are mild you should contact your local HVAC company. There could be a problem with your system.
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