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It might be called a heat pump but it can get frozen too! Yes, heat pumps can freeze, especially during the chilliest of weather, so homeowners, chill a bit! Seeing the heat pump covered in ice can be a completely normal occurrence. However, there are also instances when another issue is plaguing the heat pump. Like when the heat pump freezes up even in the heat of the summer.  

This post will discuss the various reason why heat pumps would suddenly freeze, and how homeowners can deal with these. Likewise, this article will also tackle several other reasons why a heat pump can get frozen and the possible ways to address these possible problems and prevent them from happening. 

Moreover, this blog post will introduce the defrost function available in heat pumps. This function helps the heat pump thaw the ice out of its system. This is important, especially during winter months.

How a heat pump works

To have a better grasp on dealing with a frozen heat pump, it is helpful to know the basics of how it works. Simply put, a heat pump works like a reverse air conditioner. It takes the heat outdoors and then processes it and moves it inside the home to warm the indoors. In the summer months, the heat pump takes the hot air inside the house and moves it outdoors to cool the whole house.

The heat pump is made up of two separate systems: the outdoor unit which is called the “condenser,” and then the indoor unit called the “air handler.” The condenser circulates the substance called refrigerant into the AC system so that it could absorb heat and process the heat transfer. Now heat will be transferred either outdoors or indoors depending on the direction of the reversing valve. The heat pump gets to control the direction of the flow of refrigerant through this, making it a dual-purpose indoor climate solution. It can work as an air conditioner during the summer, and then a heater during the winter months.

During the winter, the refrigerant absorbs the heat outdoors paving its way indoors to provide the needed warmth. This is done by pressurizing the refrigerant and heating it to transform it into its gas form in the compressor. This vapor then gets pushed into the air handler so that the whole house could then be heated. Once the vapor is in the air handler, it will flow into the indoor unit’s coils, and from there the cold air inside the house gets to absorb the heat from the coils. Once the heat is removed from the refrigerant, it gets circulated back into the condenser, and the cycle goes on again until the desired indoor temperature is reached.

Why do heat pumps freeze during the winter months?

After learning about the basic operations of a heat pump, it is now relatively easier to comprehend the possible reasons why it would suddenly freeze during the coldest months of the year. Since heat pumps turn vapor into liquid upon contact with the outdoor coil, condensation takes place. Condensation is the sweating of materials or vessels touched by cold substances.

When the outdoor coils get too much condensation and the temperature gets below 32F, the condensation that forms will turn into ice and freeze the coils. When this happens, a layer of ice could cover the whole unit.

How to know if the heat pump is frozen

It is easy to know if a heat pump is frozen. All the homeowner has to do is check the condenser unit outside the house and see if it is covered in frost. Check also if you have water dripping from your ac vent as this may be a sign something is frozen.

What does defrost cycle mean

As mentioned earlier, it is totally normal for heat pumps to freeze when the outdoor temperature reaches the freezing point. For this reason, heat pumps come with a defrost cycle. The defrost cycle is activated when the heat pump’s control board detects freezing within the system, the function is activated to reverse the refrigerant flow.

By reversing the flow of the refrigerant, the hot chemical substance gets sent into the outdoor coils as if the heat pump is functioning as an air conditioner. Once it reaches the coils, the refrigerant then heats it by raising the temperature and consequently thaws the ice. During this time, the heat pump can still warm the house through its auxiliary heating function. Auxiliary heating utilizes electricity to warm the house and so it is more expensive to use, however it is there to ensure that the heat pump could deliver the desired temperature when the heat pump can no longer do it on its own.

The whole defrost cycle usually takes about 15 minutes. After the cycle, the heat pump will function normally and will just activate that defrosting feature as needed.

How to fix a frozen heat pump

Before calling in a heating technician, homeowners can check several things that could have made their outdoor unit freeze up. Below are some of the areas to assess:

Inspect the outdoor unit and its surroundings

The outdoor unit should have at least a one-foot clearance from objects that could impede airflow around it. So, when the condenser gets a layer of ice on it, check its surrounding area if it is filled with debris, rubbish, snow, plants, bushes, dead leaves, and even dirt. If it is dirty, see how to clean your air conditioning condenser coils here. If it is, clear the surroundings right away because the condenser unit requires enough airflow and these objects could block it.

Another thing to check is the roof gutters. If the roof gutters cause the trickling of water into the outdoor unit then it is in essence putting water into the system that could freeze up as soon as the temperature goes below 32F. Make sure that the gutters are in good working condition to avoid the dripping of excess water into the condenser. Remember, running the defrost cycle costs a lot of energy since it taps into the auxiliary heating to keep the whole house warm while it is thawing the ice that formed in the condenser unit.

Turn off the heatpump

One of the possible workarounds, when the heat pump gets icy, is shutting the whole system off. Turn off the heat pump through the thermostat, and turn on the fan instead. Confirm that the fan is working by checking the display panel. The word “fan” should be displayed on the LCD. Hopefully, this will melt the ice off.

Call an HVAC technician

If the above-mentioned steps do not work, then the next best thing to do is to call an HVAC professional. An AC technician can easily and correctly diagnose the issue and carry out repair work if needed. 

When does a frozen heat pump become a problem?        

While it is normal for a heat pump to be covered with ice when the outdoor temperature goes below freezing point, it is never normal for the condenser to be frozen when it is not too cold outside. If your air conitioner is freezing persists, then most likely there is an underlying issue that causes the condenser to get icy.

Another indicator that freezing is not the normal kind of freezing is when the layer of ice is thick. Normal freezing only involves a thin layer of ice. Why a thin layer of ice? Since the defrost cycle runs each time freezing is detected, the current layer melts away, and then a new thin layer gets formed until the cycle is triggered once again. If the layer of ice is exceptionally thick then most likely, it is not due to weather conditions. If there is a thick layer of ice and the condenser remains frozen for a long period then it is time to seek professional HVAC inspection and repair.

Another condition that indicates a problematic heat pump, is when frost is also present in the indoor air handler. If the ice reaches the air handler then it means that the defrost function is not working. The possible reasons why the air handler could freeze include restricted airflow due to blockages, leaking or low refrigerant levels, and a failing defrost control board.

Never postpone repairs as it could do more damage to the system. Frozen air handlers could equate to even more problems because the internal parts of the heat pump are not designed to handle frost and the water that it will produce. Call for professional HVAC repair right away.

What causes problematic freezing in a heat pump

There are several common reasons why a heat pump would abnormally freeze. These include the following causes:

Poor Air Flow

Restricted airflow is one of the most common reasons why a heat pump would suddenly freeze. When there is not enough air that gets blown through the condenser’s evaporator coil then ice will build up in the outdoor unit. This is because the refrigerant cannot transform into warm gas freezing either the evaporator coil or the condensate line.

So, what causes poor airflow in a heat pump?

Malfunctioning blower fan. When the blower fan of the condenser unit is broken or fails, the heat pump cannot absorb enough heat. This is because the blower fan fails to blow air into the evaporator coils. The air prevents the coils from freezing so if it is restricted, then the coils will eventually freeze. Once the coils are frozen, the heat pump will consequently shut down.

Blocked evaporator coils and fan blades. When the evaporator coils are blocked with debris, dust, and too much filth, they cannot do their work. The clogging will impede sufficient air flow within the system, causing it to freeze. Leaves can get into the condenser and prevent the fan blades from properly turning. The same goes for snow, excessive debris, twigs, and small branches, which could all hinder the correct operation of the blades. When the fan is broken it cannot blow air into the outdoor coils causing it to freeze.

Low or leaking refrigerant

Another possible reason why a heat pump would freeze is leaking or low refrigerant levels. Refrigerant is the substance that allows a heat pump to produce warmth. The refrigerant absorbs the heat, and when there is not enough refrigerant within the system, the substance will freeze over the coils causing it to become icy. 

When the outside temperature reaches freezing levels and the refrigerant runs low, the heat pump will not have enough capability to thaw defrost the heat pump, resulting in a thick layer of ice covering the condenser unit. You may want to know how often should I service my air conditioner before you get in touch with an HVAC technician immediately to address the leak, and replenish the refrigerant.

Malfunctioning defrost control board

Every heat pump has a built-in defrost function. The defrost control board monitors whether it is time to activate the defrost cycle because outdoor temperatures have caused the formation of ice in the condenser unit. If the defrost control board is failing, then it cannot correctly trigger the defrost function, and consequently, ice will form in the outdoor unit’s evaporator coils.

Faulty Reversing Valve

The heat pump’s reverse valve is responsible for cooling the home during the summer and heating the indoors during the winter months. It directs the flow of the refrigerant so that it could either transform into a hot vapor or cool the evaporator coils. When the reverse valve is malfunctioning it cannot correctly defrost the heat pump once it freezes over due to drastically low temperatures outdoors.

 How to prevent ice build-up in the heat pump

The best thing to do to avoid frozen heat pumps is by keeping the system well-maintained. Maintenance is a dual effort between the homeowner and the HVAC Technicians. The homeowner has to make sure that filters are replaced on time, that nothing is blocking sufficient airflow in the outdoor unit, and that the air registers and vents are indoors. Homeowners should also schedule a professional heat pump tune-up twice a year for preventative maintenance purposes.

We can help you stay warm

At Reliable Standard Heating, Air, & Solar we can help you stay warm throughout the winter! Call us and we will be at your home at your preferred time and schedule. We have helped countless homeowners deal with freezing heat pumps, and we can help you too! Get in touch with us today. 

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