We’ve all heard differing opinions on whether or not we should leave the fan on our furnace running 100% of the time. I for one am confused about the whole thing and decided to get some answers. Before I get into the pros and cons I think it’s important to make sure you know the difference between “on” and “auto”.
“Auto” means that the fan automatically works ONLY when the air is being heated or cooled. So once your home reaches the temperature set on the thermostat, the fan stops.
“On” means the fan is running 24/7 even when the air isn’t being heated or cooled.
So which is better? The correct answer is “it depends”.
Why you SHOULD NOT set your fan to “on”…
Increases electric bill—Running the fan 24/7 could add about another $20-$30 to your electric bill each month unless you’re lucky enough to have a variable speed fan in which case it’ll cost about $10-$15 extra each month.
Quickly clogs your air filter—The fan will continually pull in air through your return vents, right where your air filter is. So it’s going to nab way more dust over a shorter period of time. That means you will have to change your air filter more often.
Can make you chilly in winter - The air coming through your vents when the furnace is off will feel chilly.
Higher humidity in the summer – When the air conditioner cycles off the fan will continue to run raising the evaporator coil temperature until it is above the dew point in your home. As the warm air passes through it can be reintroduced into the home off the coil or drain pan.
OK, so maybe I’m being harsh on the “AUTO” setting. Here's why you SHOULD set your fan to "on"...
Makes you more comfortable - Constant air movement can help reduce hot and cold spots…basically helping to regulate the temperature in your home.
Can help asthma and allergy sufferers - Do you have a high efficiency HEPA filter? Running the fan more often means that filter is catching more airborne pollutants that agitate allergy and asthma symptoms.
Helps dust your home - Your vacuum kicks up a ton of dust when you use it. So, before you start vacuuming, turn your thermostat to “On.” This will pull in airborne dust into your return air filter before the dust has the chance to settle again.
I debated on whether to put this one in and obviously decided to do it but keep in mind this last one is very debatable and I've seen HVAC contractors almost get in fights debating this one...
Extends the life of your fan motor - Some HVAC contractors claim the hardest part on any electric motor is the constant starting and stopping (just like stop and go traffic is hard on your car). So the folks in this camp claim that letting your fan run all the time actually increases it's life.
So what does all this mean...who knows. Personally I'm going to leave my fan running continuously in the summer. I think it helps with allergies and also makes our house a little more comfortable.
My suggestion for you...try it both ways and see what works best for your home, your wallet, and your family.
For over 35 years Rick Kelley Builders has offered full home building and remodeling services to the Central Ohio area. Check out our website by clicking HERE.