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How Should I Set the Thermostat: Fan On or Auto?

Setting the thermostat to start the air conditioner or furnace is easy. You choose either “cool” or “heat,” and adjust the temperature setting. If you’re unsure about how to use the “on” and “auto” fan settings, the following information can help.

The Fan’s “On” Setting

When the fan is set to “on,” the blower runs nonstop, regardless of whether the air conditioner or furnace is operating. One of the main benefits of this setting is that the air inside your home is filtered continuously, which can be especially worthwhile if you have an air cleaner installed in the HVAC system. Since the blower isn’t cycling on and off repeatedly, there’s also less strain and wear placed on the motor.

However, when the fan runs continuously, energy consumption and costs will rise, and you’ll have to replace the air filter more often. The major downside occurs during our long, humid cooling season, though. With the fan running, heat and humidity build up whenever the A/C cycles off and re-circulates through the living areas. This recycled humidity can overwhelm the air conditioner, increasing cooling costs and promoting mold growth. Upgrading to a variable-speed air handler is an effective solution to boost humidity control and filtration.

The “Auto” Setting

Setting the fan to “auto” allows it to operate in sync with the HVAC equipment. Whenever the thermostat signals for cooling or heat, the fan cycles on and runs until the A/C or furnace shuts off again.

Running the fan on auto during cooling season makes it easier for the A/C to keep humidity in check since it’s not struggling to remove re-circulated water vapor from the air. You won’t have to change the air filter as frequently either.

You may notice that your home starts to get warm and stuffy during those periods when the A/C cycles off. A variable-speed air handler can solve this issue too, since it runs almost continuously on low speed even when the fan is set to “auto.”

For more advice about setting the thermostat fan for comfort, humidity control and energy savings, contact Rinaldi’s Energy Solutions in Orlando.

Our goal is to help educate our customers in Orlando, Florida and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about thermostats and other HVAC topics, download our free Home Comfort Resource guide.

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