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Should I Set My Thermostat Fan to ON or AUTO?

People love their cool air in the summer and their heating system keeping their house warm all winter long. So much so they see the thermostat settings ON and AUTO and many think leaving it ON is best. But is it?

You've most likely noticed that two settings are available to control your HVAC system's blower fan: ON and AUTO. But how do you know which air circulation setting to use? In fact, what's the difference between the two thermostat settings anyway?

If you're trying to figure out which fan setting is best for your thermostat, we have all the answers you need. Here, we'll provide a detailed description of the two thermostat fan options, and we'll discuss whether your HVAC fan at ON vs. AUTO is the best option to save on energy bills and maintain the health of your HVAC system.

What Does AUTO Thermostat Fan Setting Mean?

When your thermostat fan is set to AUTO, the fan feature will engage automatically when your system is actively heating or cooling the air. As soon as the thermostat has detected that the air in your home has reached the designated temperature setting, the HVAC system will turn itself off. The fan will only turn on again once the temperature rises above or falls below the temperature setting, restarting the system.

Why You Want To Set Your Thermostat Fan to AUTO

1. Since the AUTO setting means the fan is only engaged when the system is on, rather than constantly blowing, AUTO is the most energy-efficient option between the two settings. This means you'll be using less energy and saving money on your electric bill by using the AUTO setting.

2. You won't have to replace your air filter as frequently when using the AUTO setting. When the fan blows continuously, dirt and dust particles are trapped in air filters at a greater rate. A clogged filter can lead to even more problems; your fan will have to work harder to push past all that dirt, using more energy and driving up your utility bill.

3. In summer, your air conditioning system needs time to rest so that moisture from the cooling coils can drain outside your home. When the fan runs continuously, droplets are blown back through the filter and into the air throughout your home, causing your HVAC system to work harder to pull that extra moisture out of the air.

Why You Wouldn't Want To Set Your Thermostat Fan to AUTO

1. With the AUTO thermostat setting selected, it increases humidity in the home and some rooms may be warmer or colder than you desire. This is because the system stops blowing hot air or cooling air throughout the house based on the temperature of the air closest to your thermostat rather than running continuously.

2. The frequent stops and starts associated with the AUTO setting may mean costly blower repairs since the fan wears out faster than when using the ON setting.

What Does ON Thermostat Fan Setting Mean?

When your HVAC system is set to ON, the fan will constantly blow, even when the thermostat reaches the desired temperature it was set to, and your HVAC system is not actively heating or cooling the air in your home.

Why You Want To Set Your Thermostat Fan to ON

1. If your system's fan is running without a break, the distribution of cool or warm air in your home will be more even. This lessens the likelihood of rooms without a thermostat being too cold or too hot.

2. Frequent stops and starts can put stress on your fan. Running it constantly might reduce the risk of damage and increase the life of your blower's motor.

3. With your fan constantly engaged, air will be filtered and circulated at a greater rate. This could reduce the level of dust and other irritants and make the air in your home cleaner than with the fan set to AUTO.

Why You Wouldn't Want To Set Your Thermostat Fan to ON

1. Running your HVAC system's fan constantly is less eco-friendly and may increase your utility bill as a result. Additionally, some HVAC fans are not designed or approved for continuous use.

2. Since the air in your home is being circulated at a greater rate, setting your thermostat fan to ON vs. AUTO may result in your HVAC system's filter needing to be replaced more often.

3. When it's hot outside, your fan can blow warm air into your house through ducts in your attic or near your outside walls. Your air conditioner will need to work harder to account for the added heat, increasing your energy costs.

4. The constant forced air blowing can increase wear and cause air duct leakage. And if your duct system is already suffering from leaks, the continuous blowing worsens air duct leakage.

Which Thermostat Fan Setting Is Best: ON or AUTO?

When considering keeping your thermostat fan at ON vs. AUTO, the ARS/Rescue Rooter team recommends homeowners avoid having your thermostat set to ON as much as possible.

Running your HVAC system constantly will result in higher energy costs, inefficient heating and cooling, and increased wear and tear on the blower’s motor, leading to more frequent HVAC repairs and spend more money on upkeep. Your household will be best served by leaving your setting on AUTO when you compare the effects of a thermostat fan at ON vs. AUTO.

Leave Air Conditioning Maintenance and Repairs to ARS/Rescue Rooter

Our nationwide HVAC maintenance and repair company offers expert advice and services to businesses and residences alike. We can provide installation, repairs, maintenance, or replacement of specific components of your heating and cooling systems.

We are also available to install insulation, address air quality concerns, and handle your plumbing needs. ARS/Rescue Rooter values every individual customer regardless of their means or needs, and we are proud to offer payment and financing options to suit any household.

If you have questions or concerns about using your thermostat fan at ON vs. AUTO or more general HVAC concerns, don't hesitate to get the service you and your home deserve. Schedule an appointment with one of our friendly and professional technicians as soon as possible.

Searching for more knowledge to boost your indoor comfort? Sign up for our email newsletter and you'll receive expert tips and advice from our HVAC & plumbing pros. Plus when you sign-up. you'll be entered into a drawing to win a FREE 50 Gallon Gas or Electric Water Heater!

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