Why Is My HVAC System Freezing?

Updated October 24, 2021

Why Is My HVAC System Freezing?

There are several reasons for your HVAC system to freeze up. Common causes include a dirty air filter, blocked condensate lines, refrigerant leaks, and component malfunctions. In some cases, you can correct a frozen system yourself, while other issues require a professional’s help.
 

Dirty Air Filters

For your air conditioner to function properly, it needs clean air flow throughout the system. When you have a dirty air filter, obstructions can form inside the unit. When the airflow becomes clogged the air can’t circulate, forcing the cold to build up on the coils and results in frozen air conditioning coils.
 

Broken Blower Fan

Even when your filter is clean, you need a fan to work properly to push the air through the system. If the fan isn’t functioning due to a broken motor, the airflow becomes compromised and causes the system to freeze when the cold air lays dormant on the air conditioning coils. Even dirty fan blades will reduce airflow, resulting in the same effect.
 

Blocked Condensate Lines

The condensate lines in your HVAC system are responsible for draining the excess moisture caused by humidity. The moisture is drained through pipes leading to the floor drain. If there are clogs anywhere in the condensate line, the system will freeze. If the obstruction is near the evaporator coil, the most likely issue with your system’s performance is a frozen HVAC system.
 

Malfunctioning Thermostat

The thermostat’s job is to regularly check the temperature and control how hard the air conditioner or heat pump has to work to keep consistent temperatures in your home. A broken thermostat won’t give accurate readings to your air conditioner, which results in your system running longer than it should. Forcing your system to run longer than necessary wears the components down sooner, causing your system to freeze up if the malfunctioning thermostat is diagnosed early.
 

Refrigerant Leaks

Refrigerant is what runs through your system’s coils, changing the temperature and pressure to facilitate the absorption of heat. If the refrigerant leaks, the pressure is affected and absorbs more heat than it should. When this occurs, the refrigerant lines and the coils freeze over. If you suspect your refrigerant lines are leaking, call a licensed professional immediately. Refrigerant leaks are dangerous and illegal in some areas.
 

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