With more and more households having heat pumps installed to save on energy costs, it’s important to know what to do when they break down.

One of the main problems (if any) people have with heat pumps is that they can freeze up during operation, especially in the winter. Oftentimes they are covered in ice. This is a problem because a frozen heat pump will not be able to properly heat your home.

This may happen even if the temperature is above freezing; the coil on your heat pump is generally 10 to 20 degrees colder than the outside air, so a 39-degree day can make it as cold as 24 degrees outdoors.

What Are The Signs Of A Heat Pump Freeze Up?

There are several signs that you can look for to see if your heat pump is starting to freeze up:

– Reduced airflow from the vents

– Poor heating performance

– Ice or frost on the heat pump unit

– Strange noises coming from the heat pump unit

If you notice any of these signs, it’s important to take action right away. The sooner you can thaw out your heat pump, the less damage it will sustain.

Related: Advantages and Disadvantages of Heat Pumps

What Causes Heat Pumps To Freeze Up?

When your heat pump generates heat, you will find that the refrigerant turns to gas and is compressed.

This process requires a lot of heat, which is taken from the air around the outdoor coil. If there isn’t enough warmth in the air, the refrigerant can turn back into a liquid before it has a chance to fully compress.

This can cause your heat pump to freeze up and stop working properly.

There are several factors that can contribute to this problem:

– Dirty coils

– Low refrigerant levels

– Restrictions in the flow of refrigerant

– Blocked vents or ducts

– Damaged fans

Understanding Heat Pump Freeze Ups

Your heat pumps defrost system normally has a timer that turns the heat pump off and on to prevent it from freezing. However, if the temperature outside is too cold, the defrost cycle may not be able to keep up, and your heat pump will eventually freeze up.

In some cases, you may be able to thaw out your heat pump yourself. However, this should only be done if you are comfortable working with electricity and are familiar with your heat pump’s controls.

If you are unsure of what you are doing, it is best to call a professional for help.

Attempting to thaw out your heat pump on your own can be dangerous and may void your warranty.

How To Thaw A Frozen Heat Pump

If ice build-up has been causing you problems, there are a few things you can do to try and thaw it out.

  1. First, check to see if there is ice on the coils. If so, you can try using a soft brush to remove it. Be careful not to damage the coils.
  2. Another way to thaw out your heat pump is to turn off the power and allow it to thaw naturally. However, this will take some time, and your home will not be heated during this time.
  3. If you need to thaw out your heat pump quickly, you can use a hairdryer or space heater. Place the hairdryer or space heater next to the heat pump (not too close!) and turn it on low. The warmth should help to thaw out the ice.
  4. Once the ice has melted, you can turn on your heat pump and resume normal operation.

What Is The Defrost Cycle?

The vast majority of modern heat pumps have a defrosting function that helps to prevent them from freezing up.

During the defrost cycle, the heat pump will go through a series of steps:

– The outdoor fan will turn off

– The reversing valve will change the direction of the refrigerant flow

– Warm air will be blown over the outdoor coil to melt any ice that has built up

– The outdoor fan will turn back on and the heat pump will resume normal operation

While your heat pump is in defrost mode, you may hear some strange noises or see water dripping from the unit. This is normal and nothing to worry about.

The defrost cycle takes approximately 10 to 15 minutes. The heat pump system will then operate normally, with the defrost mode activated as needed to prevent ice build-up after the defrost cycle is completed.

Why Do Heat Pumps Have Defrost Systems?

Heat pumps have defrost systems because they are designed to operate in all temperature conditions, even below freezing.

In order to do this, they need to be able to clear away any ice that may build up on the coils.

The defrost system works by turning off the heat pump and reversing the flow of refrigerant. This causes heat to be generated, which melts the ice on the coils.

Once the ice has melted, the heat pump turns back on and begins heating your home again.

How to put a heat pump in defrost mode

  1. Turn the heat pump off at the circuit breaker.
  2. Press and hold the “Mode” button. While holding the mode button, turn on the heat pump at the circuit breaker.
  3. Release the button when the word “Defrost” appears on the display panel.
  4. The defrost cycle will last for 30-60 minutes. Once it is finished, your heat pump will turn back on and resume normal operation.
  5. If your heat pump does not have a defrost cycle, you can try thawing it out yourself using a hair dryer or space heater. Place the hairdryer or space heater next to the heat pump (not too close!) and turn it on low. The warmth should help to thaw out the ice.
  6. Once the ice has melted, you can turn on your heat pump and resume normal operation.

Will emergency heat defrost your heat pump?

No. Switching your thermostat to “em heat” or emergency heat just because it’s cold outside will just cost you a fortune in energy bills.

Don’t utilize emergency heat mode unless your heat pump completely stops heating your home. If that happens, get help from a specialist heat pump repairperson.

Related: How Much Does A Heat Pump Cost To Install And Run?

Can You Pour Hot Water On A Frozen Heat Pump?

Yes, you can pour hot water on a frozen heat pump to help thaw it out. However, you need to be careful not to damage the coils. In fact, the water does not need to be boiling hot, just warm enough to melt the ice.

If you decide to pour hot water on your heat pump, be sure to use a hose with a spray nozzle. This will help prevent any water from pooling on the coils and damaging them.

Once the ice has melted, you can turn on your heat pump and resume normal operation.

Preventing Heat Pump Freeze Ups

There are a few things you can do to prevent your heat pump from freezing up:

– Keep the area around your heat pump clean and clear of debris. This will help ensure proper airflow.

– Make sure your heat pump is properly insulated. This will help keep warm air in and cold air out.

– Check the refrigerant levels in your heat pump regularly. Low refrigerant levels can cause freeze-ups.

– Have your heat pump serviced regularly by a professional. This will help identify any potential problems before they cause major issues.

Related: How Often Should Heat Ducts Be Cleaned? (ANSWERED)

Alternative Solutions (for techies)

There are a few other solutions you can try if your heat pump is frozen and you can’t thaw it out.

These are generally for people who are comfortable working with electricity and refrigerant.

Only go ahead with these alternative solutions if your unit is properly thawed out (at least 4 hours of defrosting time) and you have verified that there is no water pooled on the coils.

Resetting the breaker

Try resetting the breaker for your heat pump. This may help to reset the system and get it working again.

Check the Freon levels

Check the Freon levels in your heat pump. Low Freon levels can cause freeze-ups. You will need a professional to do this, as it requires special training and equipment.

– If all else fails, you can try disconnecting the power to your heat pump for a few minutes. This will allow the system to reset itself. However, you should only do this as a last resort, as it could damage your heat pump if not

Run the fan

Another way to unfreeze your heat pump is to run the fan (if your unit is equipped with one) for a few hours. This will help circulate the air and thaw out the ice. Simply blowing air through the unit usually thaws the unit within 60 minutes.

Start the defrost cycle manually

Sometimes you can manually start the defrost cycle on your heat pump. This will help thaw out the ice and get your heat pump working again.

The defrost cycle is activated by flipping the temperature control to “off” position, which switches off the outdoor fan and converts the outside evaporator into a condenser.

When the high-pressure refrigerant circulates through the outdoor coil, it warms up and melts any ice that has accumulated.

Move Sensor

The final alternative is to move the temperature sensor. The sensor is located on the outdoor coil and tells the heat pump when to defrost.

If the sensor is covered in ice, it can cause the heat pump to think that it doesn’t need to defrost. Simply removing the ice from the sensor can fix the problem.

Or, if the heat pump component with a sensor is exposed to direct sunlight, it will trick the heat pump to believe that it does not need to defrost.

Occasionally changing the thermostat on the outside of the device might help solve the problem.

If you intend to employ this method, make sure you label or mark the position of the sensor so that you can replace it properly.


What causes a heat pump to completely freeze up?

When the outside air is transferred to the refrigerant, which causes excess moisture to build up on your unit’s coils, a frozen heat pump occurs.
Ice and frost may accumulate on the coils as a result of this process, resulting in a total freeze-up.

Is frost on the heat pump normal?

Yes, since your heat pump is located outside, it is normal for frost to accumulate on the unit during colder months. However, if the frost build-up is excessive, it can lead to a complete freeze-up.
Solid ice build-up on the coils not only prevents it from performing at its best but can also cause damage to the unit.

Can a dirty filter cause a heat pump to freeze?

If there is a lack of airflow this is normally down to ice build-up on the coils, however, a clogged or dirty filter can also restrict airflow and cause the heat pump to work harder than normal which can lead to a complete freeze-up.

How often should a heat pump defrost?

When it is cold outside and the air temperature drops, heat pumps defrost frequently. However, the frequency of defrosts should not exceed every 35 minutes. The amount of time it takes for the heat pump to defrost will differ, but it should not take more than 10 minutes.

Can I spray antifreeze on my heat pump coils?

No, you should never spray antifreeze on your heat pump coils. This can damage the unit and void your warranty. The powerful antifreeze chemicals can eat away at the metal on the coils, causing serious damage.

When Should I Call A Professional?

If you are having trouble with your heat pump freezing up, it is best to call a professional for help.
A professional will be able to check the Freon levels, clean the coils, and fix any other issues that may be causing your heat pump to freeze up.
If you are not confident in your ability to fix the issue, or if the problem persists, it is always best to call a professional.
Heat pumps are expensive and delicate pieces of equipment, and you don’t want to risk damaging your heat pump by trying to fix it yourself.

About the Author

Passionate about helping households transition to sustainable energy with helpful information and resources.

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