Most thermostats contain the ability to control the speed of the fan, or at least set it to run on either on, or auto mode. Most thermostats only have an on or auto setting. So, what do the “on” and “auto” settings for the thermostat fans do exactly?

The “On” Setting

The “on” setting will keep the thermostat fan running all day, every day, whether the rest of the HVAC system is active or not. With the fan running all the time, the inside air is constantly being filtered. This can help keep the air cleaner, but it also makes the filter clog up faster.

Having the fan on all the time distributes the inside air more effectively. However, it can mean lower temperatures in the house during the winter months, as the air isn’t having heat applied to it constantly. Even with well insulated and sealed ducts, the air will gradually return to the temperature outside the ducts.

Keeping the fan on all the time also helps reduce wear and tear from starting and stopping. It isn’t as energy efficient as having the fan only come on when the HVAC system does.

Running the Fan on Automatic

This setting only turns the thermostat fan on when the HVAC system signals it to. It is more energy efficient, but it does not circulate the air quite as well. The filter will also last longer. On the other hand, the air isn’t as evenly distributed throughout the house. The fan also stops and starts more often.

The best way to run a thermostat fan with the on setting is with a variable speed motor. However, if your HVAC system is still running strong, you can always upgrade the thermostat, to one that includes a circulate option. This periodically turns on the fan, without requiring the entire system to come on, or the fan to run constantly.

For more expert advice about thermostats and other home comfort related questions, contact Powers Heating and Air. We proudly serve the Fayette, Coweta and surrounding Georgia counties.

Our goal is to help educate our customers in Peachtree City, Georgia and surrounding areas about energy and home comfort issues (specific to HVAC systems).

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