Any appliance freezing up in the summer seems unlikely, especially when it comes to your “heat pump” in your HVAC system. However, during the hot summer months, it’s not uncommon that this odd problem occurs, putting your HVAC system on hold and requiring a little maintenance. So, why does the heat pump freeze up in the summer?
The heat pump functions by pushing a cold refrigerant liquid through coils that cool the air around them. A build-up of condensation along the coils is common, but if the coils become too cold from the coolant, an excess of condensation turns icy and causes the pump to shut down.
While this issue is not serious, it can be tricky knowing how to solve it, and doing the wrong thing can cause further damage to your HVAC system. To help you stay informed, here’s some handy info about heat pumps freezing up.
What Unit is Freezing Up – Inside, Outside, or Both?
When troubleshooting a frosty heat pump, the first thing to consider is if the frozen unit is inside or outside (or both) as this will help determine the exact cause and solution of the problem.
Diagnosing the Problem
What Causes a Heat Pump to Freeze Up in the Summer?
There’s a variety of factors that can lead to excessive ice build-up on a heat pump. Most conditions are easy to find and fix. However, there’s always the chance a professional will be needed. Here are some common causes of a frozen heat pump.
- Dirty coil—A build-up of dirt and dust will prevent warm air from reaching the coils. Without the proper distribution of temperature, the coils will become too cold and gather excessive ice.
- Poor ventilation—Similar to dirty coils, a lack of airflow reaching the coils will limit the amount of warm air needed to maintain a balance of temperature. Make sure there are no objects obstructing airflow around the unit.
- Excessive Humidity (windows and doors are open)—For an indoor unit, too much moisture in the air will enable frost to build up. This is usually caused by open windows and doors while your AC is running.
- Low refrigerant—If the liquid refrigerant inside the system reaches a low level due to a leak in the system, an increase of pressure will result in poor circulation within the heat pump and coils. This is a common cause of a frozen heat pump and it usually requires a technician to service the system.
- Faulty fan—Another job for the professionals is a faulty fan motor. The fan is an important function for adequate airflow to the heat pump, and replacing a fan motor can be a tricky task. If the fan is functioning poorly due to dust and grime build-up, however, a simple cleaning will solve the problem.
- Thermostat—For most HVAC systems, sensors on the heat pump detect ice build-up and trigger a defrost cycle which is controlled by the thermostat. However, if the thermostat fails to initiate the defrost mode, then the ice will continue to gather on the coils and pump.
- Dirty Filter—Another common cause related to ventilation is a dirty filter. These filters should be changed regularly (every 30 days, especially in the summer months).
- Exposure to water—For outdoor units, it’s possible that the heat pump and/or coils are exposed to water. Check nearby gutters and drainage systems to make sure no water is leaking onto the unit.
How to Fix a Heat Pump That Is Freezing Up (Outside Unit)
Since outdoor units are exposed to harsher conditions, problems with the heat pump commonly involve weather damage or excessive debris. Leaves that become caught around the coils are a common nuisance and is usually the first thing to check for.
The first thing to do when a heat pump has frozen is to turn off the unit. Once the problem has been determined, and any dirt or debris has been cleared away, you can brush the ice off the coils with a soft brush or cloth, or you can use warm water to melt the ice. The summer heat will also help thaw the ice, enabling easy cleaning. Only after the ice is cleared and the cause of the build-up has been addressed, it is safe to turn the system back on.
How to Fix a Heat Pump That Is Freezing Up (Inside Unit – Ductless Mini Split)
Fixing a frozen heat pump for the indoor unit is bit easier, as the problem is likely to be less severe. Same as with addressing the outdoor unit, turn off the AC system before attempting to fix anything. Check for dirt build-up and allow the ice to thaw. A hair drier can be used to quicken this process.
If you’ve noticed that the heat pump fan is running slowly or making excessive noise, apply lubricant and clean away any dust or grime that might be slowing the fan down.
Many modern homes now use ductless AC systems. While ductless mini splits are more compact and energy-efficient, freezing can still occur. The same diagnoses and solutions apply to these types of systems as well, as mini-splits include indoor and outdoor units, heat pumps, and refrigerant coils.
Know When to Call in a Professional
Basic cleaning and ice removal will usually do the trick. However, if the problem persists, then the refrigerant level might be low, or there may be some other malfunctioning part that will require an HVAC technician. Avoid taking apart the units unless you’re cleaning the coils or replacing the filter, and if you’re uncertain about what to do, it’s best to play it safe and hire a pro.
You can have a professional come and clean your heat pump system for $130 to $200, this cleaning often fixes minor freezing heat pump issues.
Heat Pump Freezing Up FAQs
Can you pour hot water on a frozen heat pump?
Pouring hot water on a frozen heat pump is actually a safe solution. While it may be cautioned that the sudden change in temperature will crack or damage the heat pump or coils, using hot (or warm) water to melt the ice is gentler than trying to chip away are break the ice with a tool or by hand. The water shouldn’t be boiling, however, as this is unnecessary and potentially dangerous to other parts of the unit.
How Long Does Defrost Mode Last on a Heat Pump?
The defrost mode on a heat pump will run for 5 t0 15 minutes. If there’s significant ice build-up, the defrost mode will cycle through several times.
A frozen heat pump is a nuisance, especially in the summer when keeping the house nice and cool is important. But knowing what to do in the case of an icy AC unit can save you from a day of sweat, frustration and a potentially expensive repair job.
Always remember to turn the unit off as soon as you see signs of freezing, and call a professional when in doubt.