“If you make a purchase using our provided links, we may receive a commission. Learn more here.
As an HVAC professional, I've seen countless cases of heat pumps freezing up—often during the coldest days when reliable heating is critical. While this issue is common, it's rarely caused by a single factor.
In this guide, I’ll break down the most frequent reasons your heat pump might ice over, from insufficient refrigerant charge and airflow restrictions to faulty components and environmental conditions.
More importantly, I’ll provide actionable diagnostics and maintenance solutions you can implement right away.
Simple solutions for a heat pump freezing up
One: Manually defrost your heat pump
This is one of the most common issues I have seen. It usually happens in winter when the temperature is low and you have frozen coils.
What homeowners need to do:
- If you notice ice on your pump, run warm water on the sides of the heat pump.
- Make sure not to use a sharp object to crack ice, even if there’s a thin layer of ice formation. This can damage your pump.
- You can also try the defrost mode on your pump. When warm air hits the outdoor coil during the manual defrost process, it helps in melting the ice more efficiently.
- Switching your heat pump to cooling mode for a short period can help melt the ice during manual defrost.
- Turn on the fan setting so there's warm air blowing for about an hour.
- If the outdoor temperature is very low, and this doesn’t help, you can try to reverse the valve to air conditioning mode, which turns the outdoor fan off and turns the outdoor evaporator into a condenser. This melts the ice as it circulates air through the outdoor coil.
Related article: How often should my heat pump cycle on and off?
Two: Inspect and clean the coils
Dirty coils can lead to inefficient operation and freezing. I've seen many units freeze up due to neglected coils.
What homeowners need to do:
Safely clean the coils with a soft brush and coil cleaner. This should be a routine maintenance task performed at least bi-annually.
Three: Check the refrigerant levels
Proper refrigerant levels are vital for heat pump work efficiency, and low levels are a common cause of freezing.
What homeowners need to do:
This requires an HVAC system professional with a Section 608 Technician Certification, which allows them to handle refrigerants. If you suspect an issue, call a technician to check and refill it to ensure optimal refrigerant flow.
Four: Observe the unit to see if the defrost cycle is engaging
A defrost cycle periodically melts ice on the coils, preventing buildup.
What homeowners need to do:
If you notice the ice buildup on your unit is getting thicker than usual, call a technician before an even more serious problem occurs.
FYI: Here is what happens to your unit during the defrost cycle. This is basically how most units go into the defrost cycle but there are different defrost methods. Always read the owner’s manual to better understand your unit.
- 1The unit reversing valve sends the hot gas from the compressor into the outdoor coil to melt the ice.
- 2The outdoor fan stops, so no outdoor cold air blows across the coil.
- 3Auxiliary heat turns on so your home maintains the thermostat setting and keeps your home warm.
- 4Steps 1 - 3 happen at the same time. Your unit may not go into the defrost mode if there is no ice on the coil. Modern heat pumps use “time-temperature” or “demand defrost” controls and sensors.
Five: Improve the airflow around the heat pump
Adequate airflow is vital. I've seen units freeze simply because a piece of furniture was blocking a vent.
This causes the compressor coils to a lower temperature, making the heat pump indoor coil freeze.
A bad airflow in the air handler also happens because of obstructions in the ductwork or clogged air filters.
What homeowners need to do:
Ensure all air vents are unblocked and open, as blocked return vents can prevent your heat pump from running smoothly.
Also, ensure the outdoor unit has at least 18 inches of clearance all around. Depending on where you live, local ordinances may differ.
Six: Insulate any exposed pipes
Regularly changing the insulation on your pipes, especially before the winter season, can significantly reduce the risk of freezing.
I've personally seen how effective this can be in extending the life and efficiency of a heat pump.
What homeowners need to do:
Use foam insulation to cover exposed pipes. This is an easy DIY task that can prevent many cold air issues.
Ensure that all exposed pipes are well-insulated to prevent them from freezing in cold weather conditions.
Seven: Fix a failed compressor
A compressor can fail for a variety of reasons, one being that when the circuit breaker trips, people tend to just reset the breaker without knowing what’s wrong with it.
The unit could be low on oil and refrigerant or perhaps the crankcase heater has failed.
What homeowners need to do:
A good rule of thumb is that if the unit circuit breaker trips, give the unit a good look and repair any problems that you can before you reset the breaker.
If it trips again then call an HVAC technician to look at the compressor.
- 1A professional Is required: Do not work on an HVAC system if you are not trained. You can be severely injured by Arc Flash or sustain refrigerant burns to the skin and eyes.
Related article: What to do when your AC keeps tripping the breaker
Eight: Schedule regular maintenance checks
A well-maintained heat pump is essential for optimal airflow and efficiency, reducing the risk of ice forming and freezing up in winter.
What homeowners need to do:
A thorough inspection done every 12 months can identify potential issues that might lead to the heat pump freezing.
Also, keep the area around the unit clear of debris and foliage.
Related article: Understanding watt usage in your heat pump
What causes a heat pump to freeze up? (Advice for summer versus winter)
You should keep the heat pump running smoothly in both summer and winter. However, many homeowners think pumps can freeze only in winter.
In summer, your heat pump acts like an air conditioner, and issues like dirty coils and filters or low refrigerant can cause freezing up in summer.
Here are all the reasons that cause heat pump freeze up:
Related article: How to install a mini split drain line
How to prevent ice build-up on heat pump
Remove excess snow in wintertime
Remove excess snow, or you risk ending up with a frozen coil. Here's what you should do:
- 1Regular monitoring: Frequently check your heat pump, especially after snowfall or freezing rain. Ice tends to build up under these conditions.
- 2Safe snow removal: Gently remove snow from around the unit. Use a soft brush or broom; avoid hard tools that could damage the unit.
- 3Clear a perimeter: Maintain a clear space of at least 18 inches around the heat pump. This ensures adequate airflow and reduces the risk of snow drifting against the unit.
- 4Avoid piling snow near the unit: When shoveling or plowing your property, be mindful not to pile snow near the heat pump.
- 5Inspect for ice dams: Check for ice dams that can form and block the drainage, leading to water backing up and freezing.
Use the defrost mode if needed
Most modern heat pumps have an automatic defrost option. This function reverses the refrigeration cycle, sending warm refrigerant through the outdoor coils to melt ice.
You should perform regular checks to ensure the defrost option is functioning correctly. Ineffective defrost cycles can lead to excessive ice buildup.
The defrost cycle should activate periodically and only run as long as necessary to melt the ice. Overly frequent or lengthy cycles can indicate a problem.
If you suspect the defrost function isn’t working correctly, have HVAC professionals inspect and calibrate it. Incorrect settings can lead to insufficient defrosting.
The technician should check sensors and related components, as a malfunction in these parts can hinder the defrost cycle.
FAQs
How do I identify a frozen heat pump?
To identify a frozen heat pump, look for ice or frost buildup on the outdoor unit, especially around the coils. The heat pump may also stop having an effective heat mode or make unusual noises.
Can a heat pump get stuck in defrost mode?
Yes, a heat pump can get stuck in defrost mode due to faulty sensors, control boards, or wiring issues, leading to inefficient heating and potential damage.
Can you pour warm water on a frozen heat pump?
Yes, you can pour warm water on a frozen heat pump. Pouring warm water can temporarily melt the ice, but it's not recommended as a long-term solution. It can cause rapid temperature changes, potentially damaging the unit.
Do heat pumps work in freezing temperature conditions?
Yes, modern heat pumps are designed to work efficiently in freezing weather, but their efficiency can decrease as the outside temperature drops significantly below freezing. If you live in colder areas, you should get a unit with auxiliary heat unless you already have a furnace.
Related article: Best mini split heat pumps for freezing conditions
