Heat Pump FAQ: Should a Heat Pump Have Frost on It in Winter?

As the cold weather arrives, heat pumps in homes will switch over into heating mode. This means that the outdoor unit of the heat pump will draw thermal energy from the air and carry it indoors through refrigerant to release it indoors. If you notice that there is ice forming on the outdoor cabinet of your heat pump, it may seem abnormal, and potentially harmful to the heat pump’s operation.

This is an understandable concern, and in some cases it’s justified. We’ll take a close look at what this frost might mean.

The Heat Pump in Winter

Moisture developing along a refrigerant coil as it draws heat from the air is normal. You’ll notice this during the summer when the heat pump is in cooling mode: water moisture from the indoor air forms along the coil and then drips down into a condensate pan. When the winter begins, the outdoor coil will begin drawing moisture onto the coil—and it’s possible that it could freeze because of the lower temperatures.

Frost is most likely to form when the temperature is below 40°F but relative humidity is 70% or above. This is a common situation in this part of the country, so ice along a heat pump is a frequent occurrence. Heat pumps have a defense against this, which is the defrost cycle. Defrost controls periodically reverse refrigerant direction to heat the outdoor coils and eliminate frost. Most of the ice on a heat pump should vanish within an hour or two.

However, if frost continues to buildup on your heat pump, something is amiss. The defrost control may be broken, the reversing valve may have failed, or the heat pump is losing refrigerant. Whatever the issue, call for repair technicians to look into the situation and have it fixed before the heat pump starts to lose its ability to warm your home.

Raleigh Heating & Air, Inc. offers heat pump services in Wake Forest, NC.