The difference between auxiliary and emergency heat

Auxiliary heat is a secondary heat source that turns on automatically.

Emergency heat is when you turn on the secondary heat source.

The difference between auxiliary heat and emergency heat is simply the name. Both forms of heat are the exact same heat elements but are labeled differently. Heat pumps are commonly used as our primary source of heat in warmer regions. There is a limit to this unit. As long as the outdoor temperature is above 45 degrees, a heat pump can satisfy your home’s heating needs. The outside coil can and will freeze up at 45 degrees, causing the system to defrost. When in defrost mode, the outdoor unit signals the air handler to turn on the auxiliary heater. This heater is an electric heater similar to a toaster oven and will supply supplemental heat to the home while the outdoor unit is defrosting itself. Once the outdoor system is defrosted, the auxiliary heater turns off and the system continues in heat pump mode. If a heat pump system fails or is not working correctly, the homeowner must force the system into emergency heat mode. This heater is the exact same heater as the auxiliary element, only used in a different format. A heater is typically not designed to heat your home to 80 degrees, but to supplement heat while the heat pump defrosts or to serve as an emergency backup. The first function of auxiliary heat is to back up the heat pump if the thermostat differs by 3 degrees or more from the set temperature. In this case, the heat pump and heat strips will work together to create warmer air. The auxiliary heat will turn off once the thermostat set point is within 2 degrees of the inside temperature. The second function is when the outdoor system goes into defrost mode, as stated above.



link provided