Can You Run Your AC Fan with Home Windows Open?

Radiant technician smiling at camera with hands on smart thermostat

Have you noticed that on your thermostat, there is a control toggle marked “FAN”? This switch controls the A/C fan that circulates conditioned air from the cooling unit into your home. The fan can be used when the air conditioner is off as well, and often area homeowners ask if it’s OK that they run A/C fans with windows open around the house when the temperature outside is mild. Radiant Plumbing and Air is ready to address that question here on our blog.

Air Conditioner Fan Settings

Your thermostat allows you to control the fan settings for the cooling unit. Most thermostats have two settings options – ON and AUTO. The AUTO setting means the A/C fan will only run as the air conditioner or heat pump cycles to produce cooling. When you select the ON setting, the fan will run all the time, continually circulating air through the ducts and the home.

Using the A/C Fan for Better Comfort

When temperatures are mild, many area homeowners choose to turn off their air conditioners and open windows to conserve energy and keep the home comfortable. While leaving the windows open while the air conditioner runs would be an obvious waste of money, it is OK to open the windows to allow outside air in and run A/C fans.

Make sure you turn the air conditioner control to OFF and then turn the fan to ON, or else your air conditioner will continue to cycle, and your cooling energy will be wasted right out your windows! While running the A/C fan sounds about the same as running the actual air conditioner, you can tell the difference because the air coming from your supply vents will not be cool when the fan operates alone.

Without a strong breeze, simply opening the windows may not generate enough air movement to keep your living areas comfortable. In these instances, run the air conditioning fan with windows open to get air circulating throughout the home. Using the fan can help draw in fresh, cool air from an open window and force out stale, stagnant air that has gathered in other areas of the home.

When you run the AC fan with windows open like this, the fan consumes very little energy but produces valuable comfort. You can also operate ceiling fans in occupied rooms to further generate air movement and keep the home cool without the help of the air conditioner – just be sure to turn them off when everyone exits a room. Make sure you remember to adjust the fan and cooling system settings when you’re ready to use the air conditioner again, or else your system fan will operate around the clock.

Monitor Your Habits

When it comes time to close your windows and turn the air conditioner back on, be sure you also turn the A/C fan back to AUTO. It’s easy to forget this task after you run the air conditioning fan with windows open, which can cause your A/C fan to run for days on end! If you leave the fan on all the time, this heavy use will cause a noticeable increase in your electricity bill whereas using it for just a few hours on a mild day typically won’t.

If you run an A/C fan with the windows open and fail to shut the fan off when you close the windows and activate the cooling system, energy waste isn’t the only concern. The system fan will be operating many more hours than it would if it was used in AUTO mode to run only during cooling cycles. The more the fan is used, the more wear and tear it will sustain. Leaving the A/C fan on all the time can increase the likelihood of a malfunction that requires a repair, and cause the blower motor and blower fan to fail sooner than expected, requiring these components to be replaced.

With the fan cycling more frequently when you run the A/C fan with windows open, there is more air movement through your HVAC system. This means the filter will be working more, too. Leaving the fan on all the time will likely cause your filter to clog sooner, requiring replacement sooner than expected. If you discover your A/C fan was left on for a long period, check your filter to make sure it’s still in good condition, and replace it if needed.

Call Radiant and Stay Cool This Spring

Radiant Plumbing and Air is here to help you stay cool and comfortable within your home this season. Whether you need repairs to your cooling system fan or need new equipment to provide the cooling you want, we are ready to assist you.

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