Keeping your fan on "ON" during hot summers is actually working against your AC and driving up the humidity inside your home.
If you walk past your thermostat today and see the fan setting toggled to ON instead of AUTO, you might want to switch it back to AUTO.
Many homeowners believe that keeping the system fan running constantly is a good thing because it keeps air moving through the house. That's true in the winter, but during our hot summers, keeping your fan on "ON" is actually working against your AC and driving up the humidity inside your home.
What Happens When the Fan Runs Constantly
Your air conditioner has two jobs: it lowers the temperature, and it removes moisture from the air.
As the AC runs, moisture condenses on the cold indoor evaporator coil (just like water droplets forming on a cold glass of iced tea). That water drips down into the drain pan and flows out of your house.
Here is what happens depending on your setting:
When set to AUTO: The fan only runs while the system is actively cooling. When the thermostat is satisfied, the compressor and the fan shut off together. The water on the coil safely drains away.
When set to ON: The air conditioner shuts off when the house hits its target temperature, but the fan keeps blowing. This means warm, dry house air is constantly forced over a soaking-wet evaporator coil. Instead of draining away, that trapped moisture evaporates right back into the air stream and gets pumped back into your rooms.
By running the fan constantly, you are essentially re-humidifying your home every time the AC takes a break.
High Humidity Makes the Air Feel Warmer Than It Actually Is
When the fan stays on "ON," your home’s relative humidity spikes. You’ll find yourself lowering the thermostat to 68°F just to feel comfortable, forcing your system to run longer, eat up more electricity, and wear out components faster.
PRO-TIP: Leave Your Thermostat Fan Set to “Auto”
Letting the fan cycle on and off with the air conditioner ensures that the moisture pulled from your air actually drains out of your house, rather than getting blown right back into your living room. It's the easiest way to keep your home feeling crisp, comfortable, and dry all summer long.
Need help optimizing your system's airflow or checking your humidity levels?
Contact us to evaluate your system.
Caleb | Erbe Air LLC
