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Why Is My Heat Pump Covered in Ice? (Problems & Solutions)

Have you noticed ice on your outdoor heat pump unit? Some ice is normal, but too much ice can cause problems. In this article, we’ll break down why heat pumps ice over, how much ice is too much, and how to protect your heat pump in winter.

Why Is My Heat Pump Covered in Ice? (Problems & Solutions)

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Jerad Kingery


July 5th, 2022

Is Jack Frost nipping at your heat pump? 

During the colder months, heat pumps can accumulate frost or even layers of ice. And since heat pumps help keep you and your family safe and comfortable during the most wonderful time of the year, it’s natural to be concerned.

At Fire & Ice, we believe in taking the time to help our customers understand their HVAC equipment. We also write articles like this to help make HVAC information more accessible. 

In this article, we’ll cover how heat pumps work during the winter, why heat pumps ice over, and how you can protect your heat pump during the winter.

We’ll also go over signs you may notice if your heat pump has too much ice buildup and answer questions about covering outdoor heat pump units.

How Do Heat Pumps Work in the Winter?

Before we discuss why heat pumps ice over and how to prevent it, let’s briefly break down how your heat pump heats your home. 

Heat pumps are almost identical to air conditioners except for one part called a reversing valve. 

During the summer, heat pumps work like air conditioners: a substance called refrigerant travels between the coils in your indoor and outdoor units. As it moves between the units, the refrigerant absorbs heat from inside your home and exhausts it outside.

As temperatures drop and you turn on the heat, your heat pump reverses this process thanks to the reversing valve. 

The refrigerant continues to move between the indoor and outdoor units. Except to heat your home, the refrigerant absorbs heat from outside. Your system then uses this heat to heat your home.

Check out the video below for a more in-depth look at how heat pumps work.

Backup or Auxiliary Heat 

If you live in a colder climate, you may also have HVAC equipment that provides backup heat, sometimes called auxiliary heat. In many cases, this is either an electric furnace or a propane furnace.

As temperatures approach freezing and sub-freezing, your heat pump may struggle to heat your home. Your system will kick over to your backup heat source to maintain efficiency and comfort.

However, backup heat isn’t your primary heat source for a reason—it can be a more expensive way to heat your home, depending on your system. 

Heat pumps have been getting more attention in recent years. As both public and private entities explore increasing HVAC efficiency, some are taking a closer look at heat pumps. Figures such as the Biden administration and even Tesla Motors CEO Elon Musk are exploring ways to make heat pumps even more efficient. 

Why Do Heat Pumps Ice Over?

Now that we’ve discussed how heat pumps work, let’s get to the matter at hand: why do heat pumps ice over in the first place?

It’s normal to see frost or a thin layer of ice on your outside unit during the winter.

Whether heating or cooling your home, heat pumps create condensation. And in winter, cold temperatures can freeze the condensation on your outside unit.

This process commonly causes ice to build up around the sides of your unit, where your system’s outdoor coils are located. 

What Is Defrost Mode on a Heat Pump?

Because it’s normal for some frost or ice to appear on your outdoor unit, heat pumps have a built-in process to defrost the outdoor unit. You may hear your HVAC service provider refer to this process as the defrost cycle or defrost mode. 

During the defrost cycle, your heat pump briefly reverses and releases heat through the outdoor unit to remove the thin layer of ice buildup. Once the outdoor unit is defrosted, it resumes drawing heat in to heat your home.

Depending on the manufacturer, defrost cycles typically last between 90 seconds and 2 minutes. However, some defrost cycles can last as long as 5 minutes. Longer defrost cycles may also produce steam.

You may also notice ice buildup around the base of your heat pump, especially during the coldest months or in colder years. Don’t worry—this is also normal. 

Once your heat pump melts the built-up ice on the unit, the water can pool around the base and refreeze. This shouldn’t cause issues since your outdoor heat pump unit should be elevated on pump-ups.

6 Signs Your Heat Pump Has Too Much Ice Buildup

Even with the defrost cycle, your heat pump can sometimes accumulate too much ice.

So what are the six most prominent signs that your heat pump has too much ice buildup?

  1. There’s more than a thin layer of ice covering the sides and top of your outdoor heat pump unit

  2. The ice remains on your outdoor unit for one day or longer without defrosting

  3. You notice abnormally high electric bills

  4. Your heat pump is much louder than usual

  5. Your heat pump starts but doesn’t run

  6. Your heat pump doesn’t turn on at all

However, some of these signs can be caused by other issues as well. If you notice any of these signs, we recommend giving your HVAC service provider a call. 

Should I Cover My Heat Pump During the Winter?

The short answer: We don’t recommend covering your heat pump.

Although a cover could help keep your outdoor heat pump unit free of ice and other debris, it would also affect your system’s performance. To heat your home, your outdoor heat pump unit must be able to draw in air.

If you cover your heat pump, a few things will likely happen in the following sequence:

  1. Your heat pump will lock out

  2. Your heat pump will turn off until either the cover is removed or your HVAC service provider resets your system

  3. Your system will begin running on backup heat

When a heat pump locks out, safety measures trigger because the equipment can’t perform without damaging your system.

In this case, a heat pump can’t draw in enough air while it’s covered. Covering your heat pump affects how much heat the refrigerant can absorb in the heating process.

If the refrigerant can’t absorb enough heat from the outside air, the heating process can stop completely.

RELATED: Heat Pumps 101: The Ultimate List of Heat Pump FAQS 

How to Protect Your Heat Pump During the Winter

Although your heat pump already has built-in processes to protect it during the winter, there are a few ways that you can protect your heat pump:

  • Keep your heat pump free of large debris, such as sticks and tree branches

  • Change your filter as recommended

  • Be mindful of significant changes in your system’s performance

  • Schedule regular maintenance for your heat pump

Let’s walk through why each of these is important.

Keep Your Heat Pump Free of Debris

In some cases, large debris like sticks and tree branches can damage your outdoor unit or limit the amount of air your heat pump can draw in.

If you notice larger debris on or near your outdoor unit, we recommend removing it if possible.

In some cases, smaller debris like pine needles and leaves can also build up inside your outdoor unit. In those cases, your HVAC service provider can clean out your outdoor unit during regular maintenance.

Change Your HVAC Filter

No matter the time of year, it’s always important to change your system’s filter as recommended.

Your HVAC system’s filter helps remove dust and other particles from the air inside your home. However, over time, your filter can get clogged.

Clogged filters can affect your system’s performance and even damage your system over time.

Watch for Changes in Performance

As we discussed earlier in this article, sometimes you may notice changes in your system’s performance. 

It’s natural for your system’s performance to gradually change as it ages. However, if you notice any sudden changes in performance, it’s important to contact your HVAC service provider immediately.

Changes in performance can indicate building issues within your system. If these issues aren’t addressed, your heat pump’s lifespan can suffer.

Schedule Maintenance for Your Heat Pump

Regular maintenance helps ensure that your heat pump can run properly. Regular maintenance can also help catch issues with your system before you notice changes in your system’s performance.

We recommend two tune-ups for your HVAC system each year. Generally, this means one tune-up for your heat pump and one tune-up for your backup heat source.

During a heat pump tune-up, your HVAC service provider will run tests and take readings to ensure your heat pump meets manufacturer specifications. Heat pump maintenance should also include testing your heat pump’s defrost cycle. 

For more information, check out this article on what to expect from heat pump maintenance and other types of HVAC maintenance.

Get the Most Out of Your Heat Pump Year-Round

For the most part, your heat pump has built-in processes, like the defrost cycle, that keep it running throughout the year.

However, it’s also important to ensure your system receives the maintenance it needs to keep running properly year after year. This includes changing your filter and scheduling tune-ups with your HVAC service provider.

If you’re looking for an HVAC service provider in the great Columbus, Ohio, area, we’d love to help keep your system running properly! Use the zip code lookup below to see if you’re located in our service area.

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