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Troubleshooting Steps to Follow When Dealing With Frozen Evaporator Coils

Evaporator Coils

Troubleshooting frozen evaporator coils may suggest several causes for the symptom, but the actual cure usually requires the services of a professional HVAC technician. The evaporator coil sealed inside the indoor air handler removes heat from the air and transfers it to the flow of refrigerant circulating through the coil.

While the refrigerant flow is cold—around 40 degrees—it should always remain above freezing. If the refrigerant drops below 32 degrees, condensation produced by the cooling process freezes on the coil surfaces instead of draining away. As the ice formation expands, airflow through the coil is increasingly obstructed, the system begins running non-stop instead of cycling on and off, and severe A/C component damage may result.Here are some potential causes to aid in troubleshooting frozen evaporator coils:

Insufficient Airflow

Air volume through the coil affects the amount of heat energy absorbed by refrigerant. When the airflow is low, heat transfer is diminished and the refrigerant temperature may drift into the freezing range. The most common cause of low airflow is a dirty or clogged air filter. Try replacing the air filter and see if coil freezing problems resolve. If not, contact your HVAC contractor about professional service.

Lack of Refrigerant

Another reason refrigerant may drop below freezing is because there’s not enough of it in the system. A low refrigerant charge is almost always the result of a leak somewhere, and it can't be adequately resolved by simply adding more refrigerant. A qualified HVAC technician can use leak detection methods to pinpoint the leakage and make a permanent fix.

Dirt or Dust Accumulation

Continuously exposed to system airflow, an evaporator coil often becomes coated with airborne dust or dirt. This residue on coil surfaces inhibits heat transfer into the refrigerant and triggers sub-freezing temperatures. Ice forms as condensation freezes. The sealed evaporator coil is not accessible for DIY cleaning. However, coil inspection and cleaning are a standard part of an annual A/C preventive maintenance service provided by your HVAC contractor.

For more about troubleshooting frozen evaporator coils, as well as professional service to resolve the cause, contact Air Assurance.

Our goal is to help educate our customers in the Tulsa and Broken Arrow, Oklahoma area about energy and home comfort issues (specific to HVAC systems).  Credit/Copyright Attribution: “Raywoo/Shutterstock”