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Common Winter Heat Pump Problems | Frozen Coils and More

by Daniel Estevao on January 7, 2017

outdoor heat pump in winter - pacific northwest

Are you worried about your heat pump freezing during winter? Are you wondering how your heat pump even works during colder weather months? If you use a heat pump to heat and cool your home, you should know how it works and the potential problems that could develop.

Common Winter Heat Pump Problems

If you use a heat pump to heat and cool your home, you will have an outdoor unit and an indoor unit. Here are the most common problems that could develop with the outdoor section of your heat pump system.

1. Outdoor Heat Pump is Iced Over

Don’t panic. A little frost and ice buildup is completely normal. Your heat pump actually has a defrosting mechanism built in that gets rid of the ice. If you see water or vapor around your unit, it’s probably a sign that the defrost cycle is working.

Since a lot of heat pump owners are never told about the heat pump’s defrost cycle, they assume that something must be broken. Remember, a heat pump works like your refrigerator. It takes in heat from the outdoor air (even when temperatures are as low as low as -15° C/5° F) and transfers it to the indoors.

The heat pump can do this because the refrigerant that extracts the heat is colder than the outdoor temperature, and since heat flows from hot to cold (2nd Law of Thermodynamics), the refrigerant picks up heat to dump indoors.

If the refrigerant in your heat pump is colder than the dew point of the air, you will see some frost develop on the outdoor unit. A little frost is fine, but solid ice and piles of snow are NOT.

If it’s just frost, check back to see if it’s still there in a couple of hours. The defrost cycle works by passing the hot refrigerant back into the outdoor heat pump to warm it up and melt the frost.

If the frost stays on your outdoor unit for more than 3 hours, turn on your emergency heat (skip to the end for an explanation) and call a professional for service. You may have a problem with the fan or the refrigerant.

Thick frost is never a good sign. If it looks like a solid block of ice or that no air can pass through the fins, turn off your heat pump and call your local HVAC technician as soon as you can. Make sure you don’t have any gutters leaking above the unit.

After every significant snowfall, clear the area around your unit. There should be a minimum 2-foot clearance around the heat pump at all times.

2. Heat Pump Is Constantly Running

When temperatures drop below freezing, your heat pump has to work extra hard to keep up. While heat pumps are great option in moderate climates, in extremely cold temperatures they are not as efficient. Do not be surprised if your heat pump is running all day when it is freezing out. That’s why we recommend a hybrid heating system, a cross between a standard furnace and a more fuel-efficient heat pump.

If, on the other hand, your heat pump is constantly running when the temperature is above 32°F, that’s a problem; call your qualified HVAC company.

If the heat pump is not running, it could be going through its defrost cycle.

3. Heat Pump Blows Cold Air

Double-check your thermostat hasn’t been accidentally set to “cool” or air conditioning mode. Sometimes, the warm air can feel lukewarm or even cold, but that may just be because your body temperature is higher than the air coming out of your registers. Check the thermostat to see if the temperature is rising or falling.

Keep in mind that during the heat pump’s defrost cycle, you may feel some temporary cold air coming from your vents.

If your mind isn’t playing tricks on you and there is indeed cold air coming out of your vents, you may have a problem with your compressor or the valves.

Go outside to make sure your outdoor heat pump is free and clear of snow and debris. Turn the entire system off for an hour or two and try again.

What is Emergency Heat?

Your heat pump should have an “emergency heat” switch. This switch turns on the electric resistance heat as a backup heating method. In emergency heat, the electric resistance heat is the only thing that is heating your home. It will help you stay comfortable in emergencies, but electricity is far more expensive. That’s why you only use “emergency heat” in a true emergency, not just when it’s cold outside.

Some heat pumps have alternative supplemental heating, sometimes called “second-stage” or “back-up” heating, that is different from electric resistance heating. It could be gas, oil, or hot-water instead of electricity.

If you do have to use emergency heat (heat pump isn’t working), don’t use it for too long. Schedule service as soon as possible.

Make a resolution to frequently check your outdoor heat pump during the cold winter months. If you see excessive ice or snow buildup, switch to emergency heat and call for service right away! 

Related Heat Pump Information:

If you have any questions about your HVAC system, feel free to contact us at (253) 292-3995. We’ll send an expert technician to diagnose your current heating system and recommend the best options for repair or replacement.

Call Pacific Air Systems Heating & Cooling at (253) 292-3995 for 24/7 service!

Since 1984, we’ve been proudly serving our communities in Federal Way, Graham, Spanaway, University Place, Steilacoom, Sumner, Lakewood, Puyallup, Tacoma and Gig Harbor.

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