The auxiliary heater works in conjunction with your HVAC system to keep your home warm when the outside temperature is too cold for the heat pump system to be efficient on its own. The thermostat automatically activates the auxiliary heating when the desired temperature is not met by the heat pump system alone.
After some period of your thermostat not reaching the set temperature, your thermostat automatically activates the auxiliary heat.
The auxiliary heat will only shut off once the thermostat has reached set temperature.
What is Aux Heat? Everything to Know About Auxiliary Heat