Is It Better to Set Your AC’s Fan to On or Auto?

Set ACs Fan On or OffYou’ve probably heard differing opinions on how to set your air conditioner’s fan setting on your thermostat. There are two choices – “on” or “auto”. The team here at Herrmann Services has heard this question several times from customers. We put together this definitive answer to help save you money and keep you more comfortable. First, let’s explain the difference between the two settings.

“Auto” and “On” Thermostat Settings

Your air conditioner has a blower motor inside that forces the air out and through the ductwork to deliver cool air to all of the rooms in your home. The fan setting controls when this blower is on. When it is set on “auto”, the fan turns on ONLY when your system is running. When the thermostat reaches your temperature setting, the system, including the blower fan, shuts off. When the thermostat switch is set to “on”, the fan is CONSTANTLY blowing, even when your system isn’t working to heat or cool the air.

Setting the Fan to “On” Can Cost You Money

Increases Humidity

When the fan is set to “On” your AC won’t dehumidify your home as well as it should. While the air conditioning cycle is running, the indoor coil gets cold. Water vapor pulled from the air passing over the coil will condense on the coil. If the compressor is turned off, the coil warms up. The water vapor on the coil will simply sit there until the next cycle, with some of it evaporating and sitting in the air inside the coil housing. But when the fan runs continuously, the air passing over the coil as it warms up evaporates that water and puts it right back into your house raising the humidity level overall.

Higher Energy Costs

Since the fan is always running, you’re using more energy than when the fan only runs when your system is heating or cooling.

More Frequent Repairs

Obviously, when the fan runs constantly, it increases the wear and tear on your blower motor. This will lead to repairing and replacing worn parts or possibly the motor itself sooner than necessary.

If you have any thermostat, air conditioner, humidity, or blower motor questions, please feel free to call us. One of our technicians can answer your questions and even provide tips to keep you more comfortable. Call us at (513) 737-8423 or contact us online.