Auxiliary vs. Emergency Heat: What’s the Difference?

If you’ve been using a heat pump as your primary source of heating, you may have noticed the “aux” and “EM” settings on your thermostat. While they’re not used as often, they’re in place to ensure comfort during certain conditions. In today’s post, Perfect Degree HVAC discusses the differences between auxiliary and emergency heating.

How Do Heat Pumps Work?

To better explain the role of these two functions, let us first take a broad look at how heat pumps work. Heat pumps are essentially reverse air conditioners: in a standard cooling cycle, the refrigerant draws heat from the indoors and expels it through the outdoor unit. In heating mode, the cycle is reversed so the heat pump draws heat from the outdoors and releases it as warm air. While the primary source of heat is outdoor air, some heat pumps are equipped to draw heat from the ground or even under nearby bodies of water.

Auxiliary Heat

Auxiliary heat is a secondary source of heat and is activated when the heat pump is unable to draw enough heat from the outdoors. When automatically activated, heating coils are turned on while the heat pump continues to draw heat from the outside. Auxiliary heat will then turn itself off when outdoor temperatures rise or if the thermostat senses that the indoor heating requirements are met.

Emergency Heat

Unlike auxiliary heat, emergency heat is not automatically activated by your heat pump. It’s intended to be used in emergency situations, and therefore must be manually turned on through the thermostat. Emergency heating must only be used during a heat pump malfunction. When you activate emergency heating, the heat pump shuts down completely and switches to a backup heating system, usually the heating coils described above. Alternatively, some heat pumps may have an oil or gas-fired backup heating system.

Using the emergency heating function is taxing on your heating system. Heating coils are not made for long-term use, and they require high amounts of electricity. If you find yourself needing to turn it on, make sure that you schedule a service appointment with your HVAC technician.

Regular maintenance can help reduce the risks of a heat pump malfunction. When you need a service technician that you can count on, choose Perfect Degree HVAC. Give us a call at (610) 529-7372, or fill out our contact form to schedule an appointment. We serve communities in the entire Tri-State area.