Why Does My AC System Freeze Up?

This is one of the most common service requests that we receive during the summer months. And it is usually one of the easiest to correct.

Your homes central air conditioning system will freeze up mainly due to two reasons; lack of airflow and/or a low refrigerant charge. Lack of airflow can be due to several reasons, but far and away the most common reason we see is simply a dirty filter (or filters) in your duct system. Most filters are located inside the homes furnace (or air handler if the home has no furnace). Or the filters may be installed in a return air filter rack or filter grilles located outside and/or away from the furnace. It is important to maintain clean filters in your HVAC system to avoid performance issues, for both heating and cooling. Plugged or dirty filters create too much of a pressure drop across the indoor AC coil, resulting in ice building up on the coil and therefor reduced or completely blocked airflow thru the homes registers. Blocked or covered air registers, dirty blower wheels in the furnace/air handler, or improperly sized equipment or ductwork can also result in freezing issues with your AC.

Improper refrigerant levels can also result in the system freezing up. Too little of a refrigerant charge will cause low system pressures within the refrigerant circuit, resulting in icing of the refrigerant lines. This is common in older systems that have developed refrigerant leaks and are losing some of the refrigerant charge. If your system is leaking refrigerant and is more than ten years old, you may want to consider having a new system installed.