Fan On or Auto? Learn How to Properly Set Your Thermostat

Have you ever wondered about the difference between the fan settings on your home’s cooling and heating thermostat? The names of the settings, “on” and “auto,” really don’t do a very good job of explaining the difference between the two. But learning how to set your thermostat could make a big difference in energy efficiency and home comfort.

Every forced-air central HVAC system has two main phases of operation: the equipment that actually creates the heating or cooling, and the system of fans and ducts that circulate the conditioned air throughout the home. When the thermostat is set to “auto,” the fan only operates when the cooling or heating system is running. When the fan setting is “on,” the fan runs 24/7, regardless of whether the A/C or furnace is running. You can still feel air coming out of the registers; it’s just not conditioned.

While experts say the “on” setting has limited uses, such as ventilating the home when air conditioning isn’t needed, in the majority of cases the preferred setting, for several reasons, is “auto.”

Why “Auto” Is Better

• If you have an air conditioner or heat pump that’s bigger than your home’s need, it will probably cycle on and off frequently. If the fan is set to “on,” the fan will continue to blow across the evaporator coil during A/C down time. The blowing air will absorb residual moisture from the operating cycle that has collected on the evaporator coil, making your home’s air feel damp and clammy.
• Running the fan in the “on” setting unnecessarily wastes energy.
• Many people appreciate the silence between air conditioning cycles rather than having a fan humming in the background constantly.
• When the HVAC fan is running continuously, there’s more opportunity for dirty air in unconditioned parts of your home, such as the crawl space, attic, basement or attached garage, to infiltrate leaky ducts and circulate into household air, eroding indoor air quality.

For more advice on how to set your thermostat, contact Paschal Heat, Air & Geothermal. We provide excellent HVAC services to communities in Northwest Arkansas.

Our goal is to help educate our customers in Springdale, Arkansas 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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