It may sound strange that in the heat of summer your air conditioner can actually develop frost but it is possible – and it isn’t good. Understanding the causes, however, can help you prevent your A/C from freezing up. Common culprits include inadequate maintenance, a faulty thermostat and clogged air filters.
What Causes an Air Conditioner to Freeze?
- Low Refrigerant Levels
The air conditioner cools the air in your home by drawing the hot air over evaporator coils filled with refrigerant. The coils absorb the heat and transfer it outside. A refrigerant leak results in an insufficient amount of refrigerant to remove the heat from the air. Condensation builds up on the coils and eventually freezes.
- Poor Airflow / Dirty Air Filters
While the refrigerant is one part of the equation, the airflow is the other part. Without enough air being drawn over the evaporator coils, there is not enough heat being absorbed, so the coils freeze. Low airflow can result from dirty air filters, blocked air ducts, closed or blocked vents or closed dampers.
- Dirty Coils
Dirt on the coils can prevent them from functioning properly. During normal operation, condensation develops and drips off the coils. Dirt prevents the proper heat transfer between the coils and the air. The coils get too cold and freeze.
- Thermostat Issues
A poorly functioning thermostat can cause the air conditioner to run all night when it doesn’t need to. In addition to wasting energy and money, this can also cause the air conditioner to freeze.
- Closed Supply Registers
People often close the supply registers in unoccupied rooms to save money and energy, but this can actually make your air conditioner less efficient. Having too many closed could even cause the air conditioner to freeze.
- Insufficient Fan Speed
The correct balance of airflow and air pressure is necessary for the proper operation of your air conditioner. A damaged blower fan may not be running at the right speed. The resulting lack of airflow and sufficient heat causes condensation to build up on the coils and freeze.
How to Prevent an Air Conditioner from Freezing Up
- Schedule an AC tune-up
Annual maintenance by an HVAC technician is the first and best line of defense for protecting your system.
- Have the refrigerant level checked
If you suspect a problem, make sure the refrigerant level is adequate and there are no leaks.
- Change the filter monthly
Regularly change the air filter to maintain proper airflow.
- Keep the supply vents open
Make sure no more than a quarter of your home’s supply registers are closed in order to prevent freezing.
- Have the fan speed increased
Make sure the fan is not worn or damaged.
- Have the thermostat checked
Be sure the thermostat is on the correct setting and functioning properly.