Ask Our Experts: HVAC System Fan Setting – “On” vs. “Auto”

August 14, 2018 | 8:44 pm
The age-old thermostat dilemma - keep the fan
The age-old thermostat dilemma – keep the fan “on” or on “auto”?

Question for Our Experts:

Should I keep the “Fan” setting on my HVAC system on “Auto” – or is it better to just leave it “On” all the time?

Our Experts’ Answer:

Short Answer:

That depends on a number of things.  But, generally – yes, it may be more advantageous for you to simply keep your system’s fan set to “on” rather than “auto.”  And you may be surprised to learn that you may even use less energy by keeping the fan “on” continuously.  See below for a more nuanced answer.

Long Answer:

This depends on a number of things – most importantly, what your goals are for HVAC system management.  Consider the following:

  • Do you notice a significant temperature difference in various rooms within the house? If so, your system may need to be properly balanced (see our blog post on balancing an HVAC system here).  If your system is properly balanced and you’re still noticing a temperature difference, you may wish to leave your “fan” setting to “on” (rather than “auto”) so that the fan runs continuously.  This will keep air continuously circulating throughout the house and help equalize temperatures throughout your home.  We must emphasize that this may help – but is not necessarily a complete solution.  If your air distribution system (ductwork) was not designed properly or your HVAC system is not properly zoned, keeping the fan “on” will not completely solve the problem.
  • Do you utilize a specialized air filter in your HVAC system for health reasons? If so, you may wish to keep the fan in the “on” position rather than “auto.”  This will continuously (rather than intermittently) push air through the filter, providing overall cleaner air in the building.
  • Would you like to keep air circulating throughout the home, even when the air is not being conditioned? If so, keep the fan “on.”  Depending on the type and design of your system, keeping the fan on continuously may help the air conditioner to work less frequently, since temperature peaks and troughs (hot and cold) will be avoided in the building.

You might be hesitant to keep the fan “on” continuously because of the perception that a running fan will use more energy than a fan that turns off from time to time.  You’ll be glad to know that this is not necessarily the case.  In many cases, your fan actually uses the most energy when it starts up, and energy use drastically declines during normal operation.  Thus, you may actually use less energy by starting the fan up once and keeping it running rather than allowing it to turn on and off throughout the day when it’s in “auto” mode.

Need professional help with any of this?  Give Tuckey Mechanical Services, Inc. a call or fill out our online contact form – we’ve been assisting our Pennsylvania neighbors in Franklin, Adams, York, Cumberland, Dauphin, and Perry Counties for 50 years!

DISCLAIMER: This article is provided as a reference guide only. A qualified, professional contractor like the Tuckey Companies should handle all interior design, mechanical, electrical, plumbing, remodeling, metal fabrication, and restoration projects. Information presented here is of a general nature that may not be applicable in all situations. Tips, articles, and accompanying information do not represent an official recommendation of the Tuckey Companies.

All material Copyrighted (c) by the Tuckey Companies, 2019.