Should I Set HVAC Fan to Auto or On?

Your thermostat comes with three settings: on, off, and auto. On those rare days where the temperatures are perfect 24 hours of the day, you can flip the setting to off. But for the rest of the time, you have a choice to set the HVAC fan to auto or on. What should you do?

Auto means that the fan will only turn on when your furnace or air conditioner is in operation mode. Once the desired temperature has been reached, the entire system shuts down until the next cycle begins.

On means that the fan is continuously running and blowing air from your HVAC system even when the system isn’t heating or cooling the air.

Is there a right way?

Setting the HVAC fan to auto:

• When you set the HVAC fan to auto, it provides you with the most energy-efficient way to heat or cool your home. The fan will only operate when your home needs to be heated or cooled.
• The auto setting allows your home to dehumidify properly. When the fan turns off, moisture from the cooling coils can drip and drain outside. Without this process, the moist air continually blows into your home, creating a more humid atmosphere.
• You’ll also need to replace your air filter more if the fan operates all the time. The more air pushed through the filter, the quicker it will clog and grab hold of dirt particles and other pollutants.
• The blower motor does have to work harder in auto mode. You may require repair sooner, and it can burn out easier with frequent starts and stops.

Setting the HVAC fan to on:

• When the HVAC fan is set to on, the air is continually circulated throughout your home. This can help reduce hot or cold spots as there is continuous movement from room to room.
• There could be less stress on the mechanics of your system, as the fan will continually blow without having to cycle on and off.
• It may cost you more money to operate the system nonstop. Different systems operate in different ways; some may not be designed for efficiency when operating all the time.

What should you do?

Start by checking with your system’s manufacturer’s guidelines. They will prompt you in the best way to gain maximum efficiency from your furnace and air conditioner.

You can also work with your HVAC technician to ensure your equipment is working properly and is providing you with both maximum efficiency and savings.

Have additional questions? Just ask.