woman with auto thermostat

Why the Auto function might not be the best option for your furnace fan 

The next time you’re setting your thermostat, take a look at the fan option. Is it set to On or Auto? Turns out, there is a difference, and it could mean savings on your next energy bill.

What is the Auto function? 

If you program the fan control on your thermostat to Auto, the fan will come on with a call for cooling or a call for heating. After the call for cooling or heating is satisfied, the fan will shut off. 

The benefits of the Auto function: 

When there is high humidity in the house during the summertime, the air conditioner coil is wet and, if you run the fan continuously, it will rehumidify the house. Those situations are rare and it’s usually when the air conditioner is considerably oversized for the house. 

What is the On function? 

The other option is to run the fan continuously, 24 hours a day, seven days a week, 365 days a year. 

The benefits of the On function: 

There are many benefits to utilizing the On function. From a reliability and an energy-efficiency standpoint, leaving the fan on continuously is generally the best way to go. It keeps the air moving in a home, improves indoor air quality and helps to even out temperature swings, especially in two-story houses. 

Busting the On function myths 

Despite these benefits, people are likely more familiar with the myths associated with the On function. 

Myth 1: If you run the fan continuously, it costs more money and uses more energy than the Auto function. 

In reality, a motor takes a decent amount of energy to get it started, but once it’s running it doesn’t require much energy at all. The biggest use of electricity happens when the motor starts. If you let it run continuously, it will actually cost less than the Auto function when the fan is turning on and off repeatedly throughout the day. 

Myth 2: There is more wear and tear when the fan is run continuously. 

The most wear happens to the motor during the starting process when there is a lot of torque on the motor. 

Myth 3: Outside of energy and motor maintenance, it doesn’t really matter which function you use.

Lower energy costs and motor wear are great benefits of using the On function, but indoor air quality is another important factor to consider. When you let the fan run continuously, there will be more air going through the furnace air filter. The filter’s job is to collect dust and other particles from the air. For high-efficiency filters, it’s even more important to keep the fan running continuously.

Flipping the switch
These three myths can be debunked through customer education, and we train our Bell Brothers technicians and installation specialists to inform customers of the benefits of the On function of their thermostats. When homeowners do switch to the On function, they often report that their homes feel more comfortable and their heating and cooling costs are lower. 

If you’d like to know more about which fan function is best for your home comfort needs, contact us online or at 515-244-8911.