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“Auto” or “On” – How to Set Your AC Fan

Posted on August 13, 2018 by Chris Lancaster

Set Your AC FanIf you’re not really familiar with air conditioners, or maybe you’re a new homeowner and haven’t had to deal with them too much yet, you may not realize that your air conditioner has two components: the part that cools and the part that moves the air. The thermostat temperature setting adjusts the part that cools. The fan affects the part that moves the air. The blower motor uses the fan to force the air through your ductwork to deliver cool air to all of the rooms in your home. There are two choices on your thermostat for your AC’s fan setting – “on” or “auto”. So which one is best? The team at Lancaster Brothers is here to help.

“On” Vs. “Auto”

Let’s first define what the fan settings mean. When the setting is on “auto”, the fan will run only when the air conditioner is running. When the setting is on “on”, the fan will run 24/7 whether the air conditioner is running or not. So, which is better? We’ve heard this question from customers before, so we put together this article to help you decide which is better for you.


The Argument for Setting the Fan to “On”

Keeping your fan running 24/7 keeps the air moving constantly which does have some advantages.

Cleaner Air

If you set your fan to the “on” position, it will run nonstop. One advantage is that you are constantly cycling the air through your filter, which means your indoor air will be cleaner. You may want to check the filter slightly more often in case dirt builds up faster. This could be helpful if you have an allergy or asthma sufferers in your home.

Can Help Reduce Hot and Cold Spots

Keeping the fan on creates a more even distribution of heated or cooled air, which can help if you have a room above a garage or in a partially finished basement that’s hard to keep cool.


The Case for Setting the Fan to “Auto”

There are several advantages to having your fan run only when your air conditioner is running.

Lower Energy Bills

Since the fan is always running when it is set to “on”, you’re using more energy than when the fan is set to “auto”. The average air conditioning unit has a 500-watt fan, which uses almost as much energy as a refrigerator uses during the course of a year. Running the fan constantly can increase your electric bill by about $50 a month.

Lower Humidity

While the air conditioning cycle is running, the indoor coil gets cold. Water from the air passing over it condenses on the coil. When your fan is on “AUTO,” moisture is able to drip from the cold cooling coils and drain outside because the air isn’t blowing across the coils. When the fan is running 24/7, that moisture doesn’t have a chance to drip outside. Instead, it blows back into your house, and, as a result, your AC then has to work even harder to suck that extra moisture out of the air. Your home will have lower humidity levels if you set your thermostat to “auto” instead of “on”.

Less Energy Loss through Leaky Ductwork

According to Energy Star, leaky ducts can reduce heating and cooling system efficiency by as much as 20 percent. If you set your fan to “on” it will be running 24/7 so instead of air leaking out only when the AC is running, it will be a constant leak, thus increasing your total duct leakage.


Variable Speed Units Provide a Compromise between the “On” and “Auto” Settings

So, ultimately, the answer is up to you. If you have people with asthma or allergies in your home, cleaner air (the “on” position) may be your choice, but if you like the idea of energy savings, the “auto” setting is most likely your best choice. If you like the sound of the comfort and air quality improvements that the “on” setting can provide, but higher energy bills don’t sound too good, a variable speed unit may be your best choice. A variable speed unit runs nearly all the time (allowing for the advantages of the “on” setting), but it can operate at a number of different speeds depending on how much airflow is required (allowing for the energy-saving advantage so of the “auto” setting).


If Air Conditioner Isn’t Cooling Your Home, Lennox is For You

LennoxIf you experience issues with your older AC, we will be happy to take a look and either repair or replace the unit. We always recommend Lennox air conditioners because they are one of the best on the market, so if your air conditioner is starting to drag along, we will be happy to provide a free estimate. Check out our rebates and financing options for qualifying systems, and our comfort specialist will let you know about available programs.

If you have any questions about your air conditioner, fan settings, or energy savings, give us a call. One of our technicians can answer them and even provide tips to keep you more comfortable. Call us at (913) 851-3399 or contact us online.

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