Why Is My Heat Pump Freezing Up in the Winter? A Florida Tech Answers

December 17, 2019

Why Is Heat Pump Freezing Winter

If you’ve looked outside and noticed a thin layer of frost or ice on your outdoor heat pump unit, you’re probably wondering, “Why is my heat pump freezing up?”

Well, it depends!

If you notice a thin layer of frost that disappears in 30-90 minutes, this is completely normal. The outdoor air has water vapor in it, and when it’s very cold out, this water vapor can freeze, causing a thin layer of frost to form.

If you notice a thick layer of ice that isn’t going away (even while your heat pump is running), there is likely an issue with your heat pump’s ability to defrost, which means you’re probably dealing with one of the below issues:

  • Defrost control issue
  • Reversing valve issue
  • Low refrigerant

Below, we’ll look at what causes a “normal” amount of frost to form on your outdoor unit and go into more detail about the issues that can cause an abnormal amount of ice to build on your heat pump.

Want to skip to the part where a professional technician fixes your heat pump? We totally understand! We offer 24/7 emergency service, so regardless of whether you need us now or later, we can help you out. Learn more about the heat pump repair services we offer or…

A light layer of frost on your heat pump is normal: Here’s why

During the winter, you probably notice a thin layer of frost or dew on a lot of things outside, such as plants, cars, your outdoor heat pump unit, etc.

As we mentioned above, this is because air has water vapor in it. There’s a certain temperature at which this water vapor changes into a liquid, which is called the “dew point.” If the air outside comes into contact with something (car, bush, outdoor heat pump unit), that has a lower temperature than the dew point, the water vapor condenses, forming dew on that surface. And if that surface and the outdoor air around it are below freezing, that dew freezes, turning into frost.

During the winter, it’s likely that your heat pump is below the dew and freezing point because your system is full of a very cold substance called refrigerant (usually 10-20 degrees colder than the outdoor air). This causes a thin layer of frost to form on your heat pump.

If your heat pump is working properly, this thin layer of frost should be no big deal. Your heat pump should simply recognize that there’s frost on the outdoor unit and turn on defrost mode, which should quickly get rid of this ice/frost layer.

So, if you notice a thin layer of frost or ice on your outdoor unit and notice that it goes away in 30-90 minutes, there’s nothing to worry about, your heat pump is functioning just fine. However, if this frost or ice layer doesn’t go away, you may have one of the issues below.

Heat pump issue #1: Defrost control board malfunction

The defrost control board is the part of your system that controls how often your heat pump should go into defrost mode.

Parts of the board can fail, preventing your heat pump from defrosting.

Common defrost control issues include:

  • Broken thermostat
  • Issues with the defrost timer
  • Broken defrost relay

If you are having issues with the defrost control board, you’ll need to hire a technician to come and take a look. Depending on the exact issue, a tech should be able to repair or replace the part of your defrost control board that’s acting up so your heat pump can properly defrost.

Heat pump issue #2: Reversing valve issue

To defrost your outdoor unit, your system reverses the flow of refrigerant. Instead of picking up heat from outside and carrying it inside, your heat pump picks up heat from inside and carries it to your outdoor unit, melting the frost on the outside of your unit.

The reversing valve is the part of your heat pump that determines what direction refrigerant is flowing in. However, if your reversing valve is broken or malfunctioning, it won’t be able to reverse the flow of refrigerant towards your outdoor unit, which could explain why the frost/ice on your outdoor unit isn’t melting as it should.

If this is your issue, you’ll need a technician to come and repair or replace your reversing valve, depending on exactly what’s wrong with it.

Heat pump issue #3: Low refrigerant

As we mentioned above, refrigerant is the substance that absorbs heat from outside and carries that heat into your home.

If your heat pump is low on refrigerant, it won’t circulate as much heat throughout your system, which can cause your outdoor unit to freeze.

Because your refrigerant system is a closed-loop system, if your heat pump is low on refrigerant, you have a leak somewhere. To fully fix the situation, a technician will have to find the leak, repair it and then refill the refrigerant in your system. Note: Be careful of technicians who will charge you to refill your refrigerant without first repairing the leak. Otherwise, you’ll just end up paying for another refrigerant refill shortly down the road.

Want professional help with your frozen heat pump? Contact Red Cap!

If you’re dealing with one of the above issues or you think there may be something else wrong with your heat pump, reach out to our team of pros for help. Our technicians will be able to quickly determine what the problem is and fix it for you quickly.