This is normal
Probably normal: heat pump defrost
Heat pumps build up light frost in cold weather and melt it off on their own. Light frost that clears is normal; a unit encased in ice is not.
Why this happens
Carrier says light frost that melts during defrost mode is normal for a heat pump. During defrost, the outdoor fan stops for a while and you may see steam rising from the unit. Trane says once the unit exits defrost mode it should resume heating as normal.
What to do
- Wait and watch. The frost should clear and the outdoor fan should restart on its own.
- Set the thermostat to Off and switch off the outdoor disconnect, then clear snow, leaves or debris from around the unit by hand so melt water can drain away. Switch both back on when you are done.
- Don't chip at the ice or pour hot water on it.
- If the unit stays coated in thick ice, use the heat pump not heating troubleshooter.
When to stop. If the whole outdoor unit is solid ice and it doesn't clear, Carrier lists a frozen outdoor unit as a fault. Call an HVAC technician.
If it still worries you, tell the HVAC technician
- How much ice there is and whether it ever clears.
- Whether the outdoor fan runs between defrost cycles.
- The outdoor temperature when you saw it.
Build the full list: what to tell the HVAC technician.
Start this troubleshooter over
Vent, Valve & Volt is published by the team behind FourHome. Browse all FourHome replacement faucet and shower parts on the FourHome Amazon store.