Using and Maintaining HVAC Systems in Rental Properties

What Causes a Split Air Conditioner's Evaporator Coils to Freeze during Summer?

The cooling cycle of a split air conditioner begins with cold refrigerant fluid. When the unit pulls warm air out of your home, the air blows over the evaporator coils, which in turn transfer the heat to the coolant. The coolant or refrigerant flows to the outdoor unit and releases the heat to the condenser coils for dissipation to the outdoors. If there are faults in the system, the refrigerant can cool too much and freeze up the coils. Below are three potential reasons your split AC's evaporator coils may freeze despite the high outdoor temperatures.

Insufficient Airflow

For the evaporator coils to remain above freezing, there needs to be enough warm air flowing from your home into the indoor unit. The heat from the air gets absorbed by the refrigerant and warms the coils. The now cool air flows back into your indoor spaces. If there is insufficient airflow, the coolant won't adequately warm the coils, which may cause them to freeze up. 

Low airflow can cause inadequate cooling, and it occurs due to clogged filters and fans. A worn fan can also affect airflow in your home. If you notice leaks from your indoor unit and inadequate cooling, your evaporator coils may be frozen. Besides thawing the coils, you must fix the underlying problem.

Inadequate Coolant

The coolant plays a critical role in the cooling cycle. It flows into the evaporator coils and draws heat from the indoor air. The refrigerant then flows to the outdoor unit and dissipates the heat to the surroundings with the help of the compressor and condenser coils. 

Wear and damage along the refrigerant line can cause the fluid to leak. Low levels of refrigerant prevent the coils from absorbing all the heat from the home. Consequently, the coils freeze up over time. Recharge the refrigerant and repair the damaged line to restore the performance of your split AC.

Mechanical Faults

Various mechanical faults can affect the performance of evaporator coils. For example, dented or clogged coils can hinder heat absorption. Once the coils freeze, the ice prevents them from absorbing heat entirely, wreaking havoc in the entire system. Similarly, a broken fan can impede airflow to the coils and cause them to freeze. 

If you have a faulty thermostat sensor, it may record the wrong temperatures and force the AC to run for long periods. With no more heat to absorb, the refrigerant becomes too cold and causes the coils to ice over. Mechanical issues may be hard to pinpoint; therefore, you need a professional to troubleshoot the system.

The scorching summer heat doesn't prevent a malfunctioning air conditioner from freezing. If you notice water leaks from your indoor unit, contact a contractor for a diagnosis and repairs.