The short answer
If your heat pump in Northern Virginia has a thin white frost on the coil, or it’s blowing steam off the top on a cold morning, it’s working. That’s the defrost cycle, and it runs every 30 to 90 minutes when it’s cold and damp outside. If the whole unit is a block of ice, the coil is hidden, or ice is building on the fan and the top, something is wrong, and it will only get worse until someone fixes the reason.
Why a heat pump frosts up at all
In heating mode, the outdoor coil is the cold side. It pulls heat out of the outdoor air, and to do that it runs colder than the air around it. Once it’s under freezing out and the air is damp, moisture in the air freezes onto the coil the same way frost forms on a windshield. A little frost is expected. Enough of it blocks the air, and the unit can’t pull heat, so the heat pump melts it off on a schedule.
During defrost, the system flips into cooling for a few minutes so hot refrigerant runs through the outdoor coil. The outdoor fan stops, you hear a whoosh when the valve switches, and steam pours off the unit. Inside, the backup heat strips cover the gap so you don’t get cold air. Then it flips back. Aux heat and emergency heat explains what the thermostat shows while that happens.
The $67 Heating Check
We check your furnace, heat pump or boiler before winter. Through December 31. See the offer
Normal or a problem
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Swipe to see all columns →
| What you see | What it means |
|---|---|
| Light white frost evenly across the coil | Normal. It clears on the next defrost. |
| Steam rising off the unit, fan stopped | Normal. That’s the defrost cycle. |
| A whoosh, then the fan starts again | Normal. The reversing valve switching back. |
| Ice that doesn’t clear after an hour or two | Defrost isn’t working: a sensor, the defrost board or low refrigerant. |
| Thick ice on the top, the fan or one side | Water dripping on it. Usually a gutter or a roof edge right over it. |
| Unit sitting in ice or snow at the base | Melt water can’t drain away. The unit needs to sit higher. |
| Coil frosted only on the bottom few rows | Often low refrigerant. A tech needs to check the charge. |
What you can do safely
Clear snow from around the base and the top so air can move and melt water can run off. Look up: if a gutter is overflowing onto the unit, that’s the fix. Make sure the outdoor unit isn’t sitting in a puddle that refreezes every night. And check the filter inside, because a clogged filter makes the whole system work harder in both seasons.
If it’s a solid block, switch the thermostat to emergency heat so the heat strips carry the house and the outdoor unit stops fighting itself, then call. Don’t chip at the ice with a shovel, a screwdriver or an ice pick. The fins and the refrigerant tubes are thin aluminum and copper, and a puncture turns a defrost repair into a refrigerant leak. Don’t pour boiling water on it either. A garden hose with lukewarm water is fine if you want to help it along, with the power off.
Running on emergency heat costs more
Heat strips work like a giant toaster. They’ll keep the house warm, but the electric meter spins fast, so treat emergency heat as a few-days bridge, not a way of life. If the unit ices up again after a repair, or the house never feels warm on cold days, read how heat pumps handle a Virginia winter for what usually causes it.
What we check
On a frozen heat pump we look at the defrost board and its sensor, the refrigerant charge, the outdoor fan motor, the reversing valve, and where the water is coming from. Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. If it’s already iced over, book a heat pump repair instead and tell us what you see. A photo of the unit helps.
Book it
Book the heating check, call (703) 997-9757, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Is it normal for my heat pump to have ice on it?
A thin, even white frost is normal in cold, damp weather, and it melts off on the next defrost cycle, usually every 30 to 90 minutes. A thick block of ice, ice on the top or fan, or frost that never clears means something’s wrong.
Why is my heat pump steaming?
Steam off the outdoor unit with the fan stopped is the defrost cycle. Warm refrigerant melts the frost off the coil and the water steams in the cold air. It lasts a few minutes, then the fan starts again.
Should I turn off my heat pump if it’s frozen?
If the unit is solid ice, switch the thermostat to emergency heat so the backup heat carries the house, then call for a repair. Don’t chip the ice off; you can puncture the coil.
How do I defrost a frozen heat pump?
Clear snow from around it, fix any gutter dripping on it, and with the power off you can rinse it with lukewarm water from a hose. If it refreezes, the defrost controls or the refrigerant charge need a technician.
