HVAC Repair Tips


Seeing ice buildup on your heat pump’s outside unit can be alarming for you. To tell you the truth, a normal amount of ice on the outside unit of a heat pump in winter is normal. Your heat pump is designed to remedy this problem itself. However, if the ice buildup is more than normal, you should know why it’s being caused, how to stop it, and do you need the assistance of a heat pump repair technician.

When Is The Freezing Up Of Your Heat Pump Is Normal?

Believe it or not, a heat pump should have a thin layer of ice around its coils in temperatures below 32 degrees Fahrenheit or 0 degrees Celsius. This happens because of the refrigerant that flows between the coils of the outdoor unit (condenser coils) and the coils of the indoor unit or air handler (evaporator coils).

In the process of heating your home, when the refrigerant returns from the evaporator coils, it turns from vapor to liquid. Due to this, condensation forms on the condenser coils. In condensation, the water vapors in the air near the condenser coils become liquid as well and appear on the outside of the condenser coils.

As this happens in winter and in a below 32 degrees Fahrenheit temperature, these water droplets on the condenser coils turn into ice. So, this is why a thin layer of frost on condenser coils is normal in winter.

How Is Ice Removed Automatically By Heat Pumps?

Heat pumps have a defrost feature which is made to deal with the ice buildup on heat pumps in winter. There are different types of mechanisms used for triggering defrost cycles. Older systems have a timed defrost cycle that runs periodically whether the unit is frozen or not. Modern ones detect the ice level and run when needed.

When the defrost cycle is activated, it switches the reversing valve. Due to this, the heat pump goes into cooling mode. The hot refrigerant starts reaching the condenser coils (outdoor unit coils) and this melts the ice on the coils. Problem solved automatically.

When Is A Frozen Heat Pump A Problem?

You should be alarmed when the ice layer is thick and it’s not melting in days. Due to this, the ice will even form on the entire outdoor unit. You should try to fix this by understating why it’s happening because too much frost on the heat pump can damage its components.

Why Heat Pumps Freeze Up In Winter?

Wrong Location

Outside units of heat pumps must be placed outside. However, if they are on the ground level, they will become frosted more often. When a heat pump is installed, the outdoor unit is usually placed in an elevated part or the location is made elevated by special feet or anything else. If your heat pump is on the ground level, it can be elevated. However, only an expert should do it.

Gutter Or Drain Pipe Dripping On The Heat Pump

The ice buildup on your heat pump could be an external reason like a gutter or drain pipe dripping directly on the outside unit. This dripping will accumulate on the heat pump and due to the freezing temperature, it will turn into ice. So, check for any pipe or hose leaking water onto the heat pump and have it fixed.


Snowfall shouldn’t be a concern for you because heat pumps are installed outside, but in a sheltered area where snow doesn’t directly fall on the heat pump. However, in winter storms, your heat pump might still be affected. So, try to remove snow from the heat pump, when possible, in case of heavy snow.

Poor Airflow

Insufficient or poor airflow reduces the ability of a heat pump to absorb heat from the outside and transfer it inside into your home. Heat is absorbed by the refrigerant that goes to the evaporator coils in the air handler and then pushed into your house via air ducts. When this process is restricted, ice forms on the outdoor unit.

There are a few things that can cause poor airflow. So, you should do these things if you suspect that airflow problems are causing your heat pump to freeze up:

  • Clean or replace air filters in regular intervals depending on your usage and manufacturer recommendations.
  • Keep the surroundings of your heat pump’s outdoor unit clean. Leaves, debris, and snow can block the unit restricting airflow. This can also cause many other problems like damaged components and high energy bills.
  • Clean the air ducts as some parts can become dirty and act as an obstruction for the airflow. Moreover, check your air ducts for leaks.
  • Inside your house, check if anything like furniture or curtains is blocking the vents.

Improper Installation

If you installed your heat pump recently and it’s freezing up badly, it may be due to improper installation. There could be issues with the line set, wiring, ductwork, or anything else. Even something like the wrong location selection of heat pump can cause problems. For example, if the heat pump is not placed on a level and elevated surface, it can ice up and also run into many other problems. HVAC installation must be done by experts only.

Low Refrigerant

Heat pumps function by flowing refrigerant between the two coils. If the refrigerant levels are low, the functionality of your heat pump will suffer. It won’t warm up your home. Moreover, as there won’t be enough refrigerant to become warm when in condenser coils and evaporator coils, they will ice up.

The refrigerant inside heat pumps is not consumed. So, if refrigerant levels become lower, it is due to refrigerant leakage. A leakage can happen because of improper installation or rusted coils. An HVAC technician is required to check your unit, check the refrigerant level, and determine the cause of the leakage.

Malfunctioning Defrost Control Board

The defrost control board is the system that senses the need for the defrost feature to kick it in when required. But if it’s faulty, it can’t check the conditions correctly and won’t trigger the defrost cycle to activate at the right time. Because of this, ice will keep building up on the heat pump’s outside unit and the defrost cycle won’t be initiated.

With this, the heat pump will keep getting covered with ice. This will reach a point where the functioning of the heat pump will be damaging to the unit. Moreover, even if your heat pump works in this condition, it won’t warm up the house.

Plus, the heat pump might switch to backup heat which will bring a prominent increase in your energy costs.

Faulty Reversing Valve

When the defrost cycle is triggered, it activates the reversing valve that changes the heating mode of the unit to cooling mode. However, if the reversing valve is faulty or stuck, it won’t do anything even when the defrost control board triggers the defrost cycle. An HVAC expert is needed to inspect the reversing valve to fix it or replace it.

Bad Outdoor Fan Motor

The outdoor unit fan facilitates heat transfer. If it becomes faulty or obstructed due to debris or snow, your heat pump will ice up.


Various problems can cause your heat pump’s outside unit to freeze. Make sure to determine the cause of the issue and if you want to remove snow, don’t use any sharp or pointy objects. Lastly, consult heat pump repair services McLean who can inspect and fix your heat pump problems.


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