Heat Pump Iced Up in Winter: Normal Frost or a Problem?
Last updated Reviewed by Waseem Shahzad, Lead Technician
Smell gas or hear a carbon monoxide alarm? Leave the house first, then call 911 or the gas utility from outside.
Is frost on a heat pump normal in winter?
Yes. In heating mode the outdoor coil runs colder than the outdoor air, so a light layer of frost is normal on Long Island winter days. The unit melts it with a defrost cycle: the fan may stop, you may hear a whoosh and see steam, and the frost clears. That is the system working.
Defrost cycles come and go during cold, damp weather. Water dripping from the unit afterward is normal too. What is not normal is a coil that stays encased in solid ice for hours, ice building up on top of the unit, or a fan that is frozen in place.
What causes a heat pump to ice up?
Heavy icing usually comes from snow or water around the unit, a defrost control or sensor that is not working, low refrigerant, an outdoor fan that has stopped, or poor airflow indoors from a dirty filter. Water dripping onto the unit from a gutter or roof edge is a common Long Island cause.
- Snow piled against the coil or drifting over the top.
- A gutter or roof drip landing on the unit and refreezing.
- The unit sitting too low, so meltwater refreezes around its base.
- A defrost sensor or board fault, or low refrigerant.
What can you safely do about it?
Clear snow away from the sides and top, check for water dripping onto the unit, and replace a dirty indoor filter. If the unit is solid ice, switch the thermostat to emergency or auxiliary heat if your system has it, and call. Let the ice melt naturally rather than breaking it off.
- Clear snow: Gently brush or shovel snow away from the sides and top so air can move through the coil.
- Look for dripping water: Check whether a gutter or roof edge is dripping onto the unit, and note it for a permanent fix.
- Check the indoor filter: Replace a dirty filter so the indoor coil gets full airflow.
- Use backup heat if needed: If the unit is iced solid and you have backup heat, switch the thermostat to emergency or auxiliary heat.
- Call with what you see: Tell us whether the fan is turning, how much of the coil is iced, and how long it has been that way.
What should you not do?
Do not chip or pry ice off the coil with tools; the fins and refrigerant tubes are thin and easy to puncture. Do not pour boiling water on the unit or block it with a tarp while it runs. Do not keep running a unit whose fan is frozen in place.
If the house is cold and you have no backup heat, see our no-heat page for keeping pipes safe while you wait.
What does K2 do about a frozen heat pump?
We thaw the coil safely, test the defrost control and sensors, check refrigerant pressures and the outdoor fan, and look at where the unit sits and drains. If water is dripping onto it or it sits too low, we recommend a stand, bracket or gutter fix. You get the price before repairs.
Placement matters from the start: on installs like this Daikin multi-zone heat pump in Huntington, the outdoor unit location is planned for drainage and snow. Read more about how a mini-split heats a home.
Common questions
Why is steam coming from my heat pump in winter?
That is usually the defrost cycle melting frost off the outdoor coil. It is normal and stops after a few minutes.
How often should a heat pump defrost?
It depends on temperature, humidity and the model. In cold, damp weather it can defrost often; if the coil never clears, the defrost system needs checking.
Should I cover my heat pump in winter?
No, not while it is running. It needs open airflow to heat. A small roof or overhang that keeps dripping water and snow off the top can help, as long as airflow is not blocked.
Need a technician?
Call or text us 24/7 from anywhere within 15 miles of Deer Park. You get a time window and the price before any repair.
Call 24/7: (631) 414-7141