This one’s different from blowing warm air — the system seems like it’s doing something, but the house just won’t get down to temperature.
The system could be the wrong size for your home.
This is what I see most often — almost always from poor installation by someone who did a quick rule-of-thumb calculation instead of a proper load calculation. A real load calculation accounts for square footage, yes, but also ceiling height, insulation values, window sizes, which direction windows face, and how much direct sun your home gets. In Weber County, homes with large west-facing windows get blasted with afternoon sun. A system sized purely on square footage will run all day and never keep up.
Airflow through the ductwork may be the problem.
Your AC might be perfectly sized and working correctly, but if the ductwork can’t move enough air, the system can’t do its job. I’ve seen large companies install oversized AC units on existing ductwork never designed to handle that airflow. The result? The system runs constantly, the house won’t cool, and eventually the evaporator coil freezes up.
Airflow is the number one killer of cooling performance in the home. Not refrigerant. Not brand. Airflow.
The evaporator coil might be dirty or frozen.
A coil coated with dust can’t transfer heat properly. If you suspect a frozen coil, turn cooling off and switch to FAN ONLY at the thermostat for a few hours to defrost. Once thawed, a technician can properly diagnose the cause.
By Gregg DeMille, owner of Timber Creek Services in Farr West, Utah.
Need help with this? See AC Repair or call or text (801) 832-5302.