What does auxiliary heat mean?

Sometimes the thermostat on your heat pump may read AUX HEAT. What does auxiliary heat mean? Does it mean there is something wrong with your heat pump? This is a common question we get from heat pump owners, especially those new to this type of heating. Heat pumps use less energy to heat homes than furnaces. However, they are designed to be used in warmer climates where the temperature rarely drops below freezing.

In below freezing weather, heat pumps rely on a backup heating method when the heat pump cannot reach the desired indoor temperature. This backup system is called “auxiliary heat.” It is perfectly normal, and you have nothing to worry about.

To understand why your heat pump isn’t effective in extreme cold, it is necessary to know how heat pump technology works:

• Heat pumps use a series of coils filled with refrigerant
• These coils draw warmth of the the air outside
• It then moves that through the ducts and out through the vents

When the air temperatures outside are extremely cold, the heat pump cannot pull enough warm air out of the air outside, so then the auxiliary heat must come on to heat your home.

Another complication for heat pumps in extremely cold weather is ice. If the outdoor unit or coil gets frozen over with ice, it is unable to do its job. Heat pumps are designed with a built-in solution for this problem: a defrost cycle. The defrost cycle basically switches the heat pump over to the cooling mode so that the heat from inside your home will be pumped outside to melt the ice on the outdoor unit. While this is going on, the auxiliary heat is required to keep your home from getting cold.

There may be cause for concern if your auxiliary heat continues to run once the outside temperature begins to rise. Prolonged use of auxiliary heat can cause a noticeable rise in your utility bill! If you notice this is happening, please call LHT Cooling, Heating & Refrigeration, Inc.!