Everyone appreciates the efficiency and all-in-one performance of heat pumps, as they effectively provide air conditioning in the summer, and warmth in the winter. However, sometimes they develop a coating of ice, leaving users with questions like: why do heat pumps freeze up?
In addition to letting you know why your heat pump froze up in winter, we will explain if it’s normal, when it should be considered a problem, the effects, andp how it can be fixed. Keep on reading and you would know what to do about frozen heat pumps in winter.
Is it Normal for Heat Pumps to Get Iced Up in the Winter?
Firstly, can heat pump freeze up in winter? Yes, it can. It is normal to see ice on heat pump in winter. Basically, the outside unit freezing up in winter can be attributed to the heat pump’s working system, which involves the refrigerant turning to gas and then condensing as it comes in contact with the outdoor coil. In colder climates, this condensation process easily results in freezing.
Thankfully, heat pumps are manufactured with an anti-freezing function that curbs this problem. This is an important feature, especially for heat pumps used in cold climates. The heat pumps have a defrost cycle that automatically switches on when they reach a certain temperature. This way, the unit is prevented from icing over completely.
A cold climate air source heat pump is equipped with temperature sensors that help trigger the defrost function into action. It also comes with a timer, requiring the compressor to operate for a given time before the cycle begins. The duration for this can be set to 30 minutes to 2 hours depending on the manufacturer.
Some manufacturers design the anti-freezing system to start the time after the sensor has signaled the frost. Other manufacturers set the timer to after the completion of the last defrost cycle, ignoring the sensor. Most defrost functions are limited to a cycle of 10 minutes max. Actually, this is more than enough to fix your frozen heat pump in winter.
When are Frozen Heat Pumps Considered a Problem?
Typically, the anti-freezing function is all that it takes to thaw a heat pump freezing in winter. However, there may be occurrences when the defrost cycle isn’t enough to keep up with a heat pump icing up in winter.
When a heat pump has ice on its system for too long, it may cause malfunctioning or even damage the system’s mechanical components. This means that not only will the coils be unable to pull cold air from your home’s interior, the system’s heat output capacity will also be impaired.
In fact, if you leave the heat pump to continue working when it is impossible for air to pass through the fins, there can be more damage, such as broken fan blades, refrigerant leakages, and impaired outdoor coils.
If you see the following signs, then the heat pump may really have a problem
- The air can not be pulled into the fins.
- The heat pump unit has been completely frozen for a long time.
- The top and inner coils of the heat pump are encased with ice.
- You can see that there is frost on the coil, but the defrost function is not activated.
To avoid this problem, it’s best to call a certified HVAC technician to thoroughly inspect your domestic heat pump system.
What are the Effects of Heat Pump Freeze-up in Winter?
Heat pump icing up in cold weather cause several negative effects, which includes:
- Reduced Efficiency: Ice buildup on the heat pump’s coils blocks heat exchange. This reduces the system’s heating efficiency, resulting in increased energy consumption.
- Increased Operating Costs: Because of the reduced heating capacity, the heat pump needs to work longer to compensate for decreased efficiency, resulting in higher energy bills.
- Risk of Damage: Repeated freeze-thaw cycles can damage the heat pump’s mechanical parts like the fan blades, refrigerant, and coils, which causes extra costs.
- Inadequate Heating: In severe cases, extensive ice buildup can cause the heat pump system to completely shut down or deliver inadequate heating, leaving your home cold.
- Shorter Lifespan: The effect of frequent heat pump freeze up in winter and the strain on the heat pump system results in reduced useful life.
What Causes Heat Pump to Freeze Up in Winter?
Below, we will answer the question: why does my heat pump keep freezing up? Actually, there is no singular reason for this despite the fact that heat pumps come with defrost features that ensure they continue to work perfectly despite the conditions they are exposed to.
Basically, there are about 5 reasons associated with the “why does my heat pump freeze up” question. They are:
Technical Malfunction
Despite the fact that heat pumps have a simple working principle, in actuality, it’s a slightly complicated appliance with many moving components. Also, the outdoor unit is exposed to some pretty harsh elements throughout the year, especially if you live in colder environments. Because of this, it doesn’t come as a surprise if a part of your heat pump fails to work overtime.
Listed below are some technical issues that can cause your heat pump to malfunction and freeze up during winter.
- Low refrigerant levels (refrigerant leakage): If there isn’t enough refrigerant in your heat pump, it cannot absorb as much heat as is needed, making the coil freeze if exposed to a very cold climate. Also, if your heat pump was produced long ago, it may be using Freon R-22, a refrigerant that has been phased out due to EPA guidelines.
- Faulty defrost control board: This board controls the response of the defrost function to freezing heat pumps. If it malfunctions, the defrost process and cycle timing will be compromised, resulting in a frozen coil.
- Faulty reversing valve: The reversing valve is the major difference between the air conditioner vs heat pump. Its purpose is to change the direction of the refrigerant, making the heat pump perform both heating and cooling functions. If the reversing valve is faulty, your heat pump won’t be able to defrost properly when it begins to freeze.
- Damaged fan motors: When the fan malfunctions and doesn’t blow enough air over the outdoor evaporator coil, the coil will freeze, leading to the heat pump’s shutdown.
Blocked Airflow
The major catalyst of heat pump working principle is airflow. It not only transfers the heated air inside your home but also moves air from inside the house to the outside environment. So, when this airflow becomes blocked, air cannot pass over the evaporator coils sufficiently. This makes the coils cool to an inappropriate temperature, resulting in heat pump freezing in winter. Examples of scenarios that cause blocked airflow are when there are leaves or trees around your heat pump. Another is when there is a clogged air filter on your heat pump system.
Too Much Moisture
Major elements you shouldn’t allow get trapped in your heat pump are water buildup and extra moisture. They are not your friend, hence you should prevent any means through which water can penetrate into your heat pump.
Situations such as a broken gutter that gives way for excess water to pour on your heat pump, or ponding of water at the base of your heat pump should be avoided. They can significantly increase the chances of having a frozen heat pump in winter.
Lack of Maintenance
Even though heat pumps are built to be strong and last for over 2 decades, they still require maintenance at least once a year by a heat pump expert. Doing this yearly will ensure that the heat pump retains its efficiency throughout its service life.
During maintenance, the HVAC expert will conduct a full check of the system and carry out processes like changing the air filters, cleaning the outer evaporating coils, lubricating the fan motors, etc.
Placement
The base where your heat pump is placed is very important. It shouldn’t be standing on the ground because it can be exposed to groundwater or located where water runs into it. This can increase the chances of your heat pump freezing in winter.
How to Fix Heat Pump Freezing Up in Winter
What to do if heat pump freezes up in winter? Well, there are several steps to thaw heat pump systems. They include:
- Inspect the air filters. Good airflow is a cogent step on how to keep heat pump from freezing in winter. If it is clogged or dirty, it can significantly affect the air flow. So, clean or replace the air filters when necessary.
- Ensure the air vents and cool air intakes are not restricted. Don’t put furniture or any object too close to your heat pump air vents and registers. Also, don’t pile boxes or any other objects in front of them.
- Repair broken gutters and clean overflowing ones that deliver water into the heat pump system. When gutters get blocked with leaves, they can overflow onto your heat pump, causing it to freeze. If you don’t have gutters on your house, install them so water won’t flow onto your heat pump.
- Another thing to check is the ground level. At all times, the leveling should be equal. A part shouldn’t be higher than the other, as this can impede the drainage path for any ice that’s melted during the defrost cycle. Also, it can restrict air flow, which contributes to ice buildup. This is why it’s best to place your heat pump on a concrete slab that’s at least a few inches above the ground.
- After all these are done and your heat pump is not back to working effectively, go indoors to manually turn on the fan at the thermostat. If the vents don’t start giving quality output within a few minutes, then the problem might be with the blower motor. At this point, it’s best to call an HVAC expert.
- Periodically schedule a routine check with your heat pump expert. This will go a long way to prevent conditions that eventually lead to heat pumps freezing up in winter.
Antifreezing Measures for Air Source Heat Pumps in Winter
When entering the cold winter season, we need to prevent the water in the air source heat pump system from freezing and expanding, which results in damage. In order to enable you to better use the heat pump system and avoid the failure of heat pump units, it is necessary to operate the heat pump units according to the air source heat pump user’s manual or instructions. At the same time, prepare well for anti-freezing in winter to ensure the safety and normal use of your heat pump system, avoiding the freezing damage and unnecessary loss of the air heating system caused by power failure, water shortage or improper operation.
Pipe Insulation
When the ambient temperature reaches the freezing point, the water temperature of an source heat pump water heater drops quickly. If the hot water pipe and the return pipe do not take insulation measures, the heat consumption will be accelerated. Air source water heaters mainly use thermal insulation cotton or polyurethane foam for pipe insulation. Small pipes are generally insulated by thermal insulation cotton while large ones are often insulated by polyurethane foam.
Ensure that heat pumps are powered on when they are in normal use.
Maintaining the heat pump’s power supply in winter cannot only ensure that the air source heat pump water heater can provide hot water all day long and but also make sure that the unit does not frost so that it can run normally. Both air source heat pump water heaters and heating units could start their automatic anti-freezing protection function when the outdoor temperature is low in winter.
When heat pump units are not used in winter, water should be drained in time.
If the air source heat pump unit does not run in winter or needs long shutdown, such as frequent power outage and shutdown at night, the water in the system should be emptied to prevent any freezing damage. And the power supply should be cut off with a protective cover to cover up the unit. When running again, please check the system thoroughly before starting.
Antifreezes must be added to the air source heat pump unit if water is not drained.
According to the specific use of customers, when the water in the unit is inconvenient to drain and empty in winter and the water or power may be cut off, the whole air source heat pump heating system must be added with antifreeze fluid. The selection of antifreeze fluid must be based on the local minimum temperature as an important parameter.
Dealing with a Frozen Heat Pump
If it is found that the air source water heater pipeline has been frozen but not cracked, do not knock on the pipeline or pour hot water on the pipeline. Just wait for its natural melting.
About SPRSUN heat pumps for winter. 
Founded in 1999, SPRSUN has been providing various clients around the world with quality heat pumps wholesale, and have earned the reputation as one of the leading global heat pump manufacturers. We use advanced technologies to surpass the norm and invent modern low ambient heat pumps that can withstand harsh conditions, especially in cold areas. Our products are popular in colder regions like Finland, Sweden, Denmark, Japan, Germany, and so on.
Equipped with our self-developed anti-freezing technology and Panasonic Enhanced Vapour Injection (EVI) technology rotary compressor, our heat pump works efficiently and defrost quickly in cold climates where the ambient temperature range is between -30⁰C to 50⁰C. For top-quality heat pumps with anti-freezing function, look no further than SPRSUN. Our products are tested and trusted and verified by various regulating organizations, such as MCS, ISO, CE, CB, KEYMARK, SAA, CCC, and ERP.
How SPRSUN Heat Pump Anti-Freezing Systems Work
SPRSUN independently developed its PID intelligent defrosting control mode. The defrosting time does not exceed 20% of the operation cycle. By detecting the ambient temperature, evaporator coil temperature, and compressor return gas temperature, the PID intelligent defrosting control mode calculates the temperature difference and the accumulated working time of the compressor to judge the frosting conditions of the evaporator.
When the defrosting conditions are met, the defrosting mode will be automatically entered to prevent the unit from defrosting confusion and energy consumption, which will improve the reliability and economy of the whole unit.
How SPRSUN heat pumps defrost mode works in Latvian climate:
Project – Mārupes novads, Latvia. Equipment – SPRSUN Black model 16 kW