Heat pump covered in ice
A light frost on a cold, damp morning is normal. A block of ice that won't go away is not.
Normal
In winter the outdoor coil collects frost. Every so often the heat pump runs a defrost cycle: the fan stops, you may hear a whoosh, and steam rises for a few minutes. Then it goes back to heating.
Not normal
- The coil, top or sides stay coated in solid ice for hours.
- Ice builds up on the top panel and fan.
- The house isn't keeping up and the thermostat stays on auxiliary heat.
What you can do
- Make sure gutters aren't dripping onto the unit, and clear snow or leaves from around it.
- Replace the indoor air filter. Low airflow can make defrost less effective.
- Switch the thermostat to emergency heat to keep warm and give the outdoor unit a break. Don't chip ice off the coil, you can damage the fins.
Usual causes
A failed defrost control board or sensor, low refrigerant from a leak, a bad outdoor fan motor or a stuck reversing valve. A technician can diagnose it with a few tests.