HVAC: AC fan - Auto, ON, or Circulate? (furnace, windows, AC)
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Just moved into a new house, the thermostat had the AC turned off
and the fan set to ON.
I didn't pay much attention to it.
I opened some windows to let some fresh air in and cool the house down.
The fan continuously running sorta started to bother me so I turned the fan to Auto.
For as long as I've been a homeowner, this is the first time that I can recall
the fan being on while the AC was turned off.
For the most part it was AC/Heat is either on or off.
I never turned the fan on or auto.
Got me thinking, what mode should the fan be set on when your AC/Heat are turned off?
My options on my thermostat are : ON - Auto - Circulate
Aside the obvious, what the difference between ON vs Auto?
Is one mode better than the other?
Now, if your AC/Heat are off and your fan is running, it's going to dirty up your filters quickly?
I ask that because I changed the air filters and they were disgusting, as in they hadn't been
changed in a very long time. I mean a very long time.
Or it was just that they had the fan running all the time??
You might turn the fan to manual "on" if for instance your bathroom smells musty, and you don't want the person who just bought your house to notice right away. Or, if you had a wet floor, and was trying to expedite the drying by circulating as much air as possible. Do you have a finished basement? Could be a problem with wet basement too, trying to dry that out, using the furnace to exchange air with the upstairs.
I select the fan in Auto mode about 99.9% of the time. Then I will select heat or cool as needed. Only on VERY RARE occasions do I run the fan constantly, and then only for a specific reason, usually with the heat/air turned to Off.
Just moved into a new house, ....
I ask that because I changed the air filters and they were disgusting, as in they hadn't been
changed in a very long time. I mean a very long time.
If it's a NEW house, why would even be dirty at all, unless the work crew tracked lots of dust into house while building/finishing it out and had it running constantly while working?
Maybe it was clean on move-in/new, but bringing in all your old stuff had lots of dust in/on it, and the filter just happen to catch it out of the air while the blower was constantly on?
Either way, the filter is doing what it's supposed to do, catch dust out of the circulated air.
Normally, the fan setting should stay on AUTO, unless you have special reason to constantly have it on, which uses lots of electricity.
During hot weather, when running AC and windows are shut, you really should have it on AUTO, as leaving it on ON will cause the water/condensation on the inside coil to be evaporated/pulled back into the house/rooms making it more humid/sticky, rather than drip off and leave via the condensate line keeping the inside of the home dryer.
On will run continuousy. Auto will come on to blow cool/heat as required.
Yes I understand that.
My question was more of is there an advantage of having set to ON vs Auto.
Thanks everyone for all the help.
Like I said, in my previous homes, the AC/Heat was either on or off.
I don't ever recall messing with the fans.
I saw the option on the thermostat for the fan but I didn't bother with it.
And now, the dang fan was set to ON and it threw me off.
Yes I understand that.
My question was more of is there an advantage of having set to ON vs Auto.
Thanks everyone for all the help.
Like I said, in my previous homes, the AC/Heat was either on or off.
I don't ever recall messing with the fans.
I saw the option on the thermostat for the fan but I didn't bother with it.
And now, the dang fan was set to ON and it threw me off.
I'll just leave it on AUTO then.
Thanks again!
Good decision. Auto is the generally the best setting.
I can see the on setting used permanently for whole home filtration. Someone with a health issue could use a high MERV rated air filter to constantly filter the home’s air. Another option is for temporary use like to help remove smoke or food smells from cooking. This being a newly built home I wonder if the builders set it to on because of the paint, caulking, and chemical smells from new building materials.
as to filter dirty and dust in the house,it has t o do with all the auto traffic in your area.I use the robotic sweeper every 2 weeks and with windows closed,there is always a lot of white dust.
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