HVAC experts- run AC fan setting auto or on ?

[scottie]

Moved into a new home with a recently replaced higher end AC unit/furnance. In the past always just set thermostat to "auto" for the fan setting in summer. Home inspector suggested leaving the fan set to "on" instead. Wasn't sure which setting was better to use and also wear/tear and any utility cost impact.

 

[RNMOM]

When you put the setting on 'auto' the air conditioner or furnace will come on when the temp you set it for is not met. The fan will blow only when the unit is working.

If you put it to 'on' the fan will all the time. ALL the time. Frankly, it drives me crazy to have it on all the time. My DH runs ours when we have the carpets cleaned to help the air circulate and dry the carpet faster.

Either is probably okay but I prefer to have a ceiling fan on in the rooms we use most to help run the air conditioner less often.

 

[Luvchefmic]

Just had the contract tune up cleaning last week The tech said leave it on " auto " to avoid the constant running and the added expense I'm glad I have been doing it correctly my monthly bills are very reasonable
Not sure why your home inspector would say that ?

 

[ilovemk76]

If you mace multiple zones or a single zone and the house temp seems even, then use auto. If you have a section of the house that gets hotter, such as a second floor, then on will help to distribute the cool air better.

 

[ronandannette]

Just had the contract tune up cleaning last week The tech said leave it on " auto " to avoid the constant running and the added expense I'm glad I have been doing it correctly my monthly bills are very reasonable
Not sure why your home inspector would say that ?

I manage the warranty department for a large homebuilder and while we DEFINITELY do not live in A/C country, I'm going to use the principles of winter heating to explain it. Modern high-efficient HVAC systems are designed to actively pull fresh air into the building envelope and actively duct interior air out. Also, whether heating or cooling, the system responds to whatever temperature is read right at the thermostat location, not talking other areas of the home into account. Running the fan constantly (which, by the way, it is designed to do - it is a variable speed fan which self-adjusts to minimize wear and tear) provides much more even heating and cooling to all rooms and improves the quality of indoor air by exhausting humidity and catching contaminants in the filters. Today's homes are built "tight" for energy efficiency and without active ventilation you essentially live in a zip-loc baggie. Electrify usage does come into play but should be minimal given efficient design. Some old-school HVAC contractors, more familiar with past mid-efficient systems (which don't work the same way) might advise against running the fan but we believe that to be a mistake. Bottom line - operate it however you want, but it really is designed to be optimum in the "on" position.

P.S. Changing/cleaning the filters regularly is the single, most important aspect of minimizing wear and tear on your fan motor and maximizing your indoor air quality. My company voids warranty on furnaces if we find the filters to have been neglected.

 

[JanaDee]

I manage the warranty department for a large homebuilder and while we DEFINITELY do not live in A/C country, I'm going to use the principles of winter heating to explain it. Modern high-efficient HVAC systems are designed to actively pull fresh air into the building envelope and actively duct interior air out. Also, whether heating or cooling, the system responds to whatever temperature is read right at the thermostat location, not talking other areas of the home into account. Running the fan constantly (which, by the way, it is designed to do - it is a variable speed fan which self-adjusts to minimize wear and tear) provides much more even heating and cooling to all rooms and improves the quality of indoor air by exhausting humidity and catching contaminants in the filters. Today's homes are built "tight" for energy efficiency and without active ventilation you essentially live in a zip-loc baggie. Electrify usage does come into play but should be minimal given efficient design. Some old-school HVAC contractors, more familiar with past mid-efficient systems (which don't work the same way) might advise against running the fan but we believe that to be a mistake. Bottom line - operate it however you want, but it really is designed to be optimum in the "on" position.

P.S. Changing/cleaning the filters regularly is the single, most important aspect of minimizing wear and tear on your fan motor and maximizing your indoor air quality. My company voids warranty on furnaces if we find the filters to have been neglected.

OP, ours is set to auto for both furnace and c/a. I don't want the fan running constantly. We use ceiling fans to help evenly distribute air throughout the house.