More efficient way to run air conditioning?

[WhiteKitties]

I remember someone telling me that my A/C will work better and use less energy overall if I set the fan to run continuously, because the unit is still cold when it shuts off and keeping the fan running will pull that cool air out and circulate it, and also keep the air in the house circulating evenly. I don't know if this is true or not, but I'm certainly looking for the most efficient (cheap) way to run the A/C. I'd rather not run it at all, but once my house gets above 85 degrees, with the humidity we have in Chicago, I just can't function. I'm really missing my parents house with its huge trees, because 85 and humid in a shaded house is a lot more comfortable than 85 and humid in a house with no shade over it! (I have trees, but they're only three years old and half the height of the house!)

[Heidi n Q]

I'm no help. Our AC unit is waaaay undersized. 95* outside and 84* inside. Ugh!
Husband finally broke down and bought two small window mount AC units last week. One in the Go-to-**** room and the other in the kitchen. We're using two box fans to direct air down the hall and into the Master BR and Office. We aren't keeping our AC fan running, only because the air would be heated through the ducts up in the hot attic and defeat the cooling purposes. I want to better insulate them, and then we could do that. I do have the AC on but it is set fairly low and it will circulate a bit when it comes on but in the meantime, we're using the 2 window ACs and the boxfans.

*the GTH room is the spare bedroom with a full-size bed, TV and his laptop. We enjoy calling it the GTH room, because when we are in the living room watching TV and we each want to watch something different, I get a kick out of telling him to GTH and watch whatever he wants to watch. Or he'll tell me he's GTH to watch whatever he wants to watch.

[hpi]

Hm I'm not help neither but the central air unit here is set to fan on when it's hot out and when it's not it's just set to fan auto.

When it's 30C out and high humidity outside it's 19.5C inside the house and it feels goooood!

[Leazie]

I know that I read something recently about leaving the fan on when the ac was not working correctly, but it does make sense to use it at all times. I hope you find out for sure because I would like to know also.

[gunterkat]

Leaving the blower running is more efficient if your ductwork is not well insulated and/or leaking. Not only does it make use of the residual cooling left in the evaporator coil (cooling part ) but it doesn't allow the air in the ducts much time to collect heat from the attic. When I lived in Metairie I placed a small fan inside the return air space tp keep air moving in the ducts. It cut my summer electricity bill by about $30 a month, and kept my apartment cooler.

[izcaturday]

Aside from the fan being the second-most energy consuming part of your AC..... there's no reason not to leave it on more than a few minutes after your compressor turns off.

A few minutes after the compressor turns off, the evaporator is near ambient temperature. Therefore, its not doing anything for you. As for the duct work. If you have so much duct work that you can't blow the hot air out in a few minutes, you've got a serious problem anyway.


As a summation.... leaving your fan on for a few minutes is fine. After that, you're just speeding the heating process from solar radiation and not saving yourself much at all because the compressor is on more often and that is what uses the majority of your energy.

[Mom of 4]

Ceiling fans, the decorators nightmare.
In the summer they are set to pull cool air up from the floor and in the winter they are reversed and pull the hot air down from the ceiling. Ours are on all of the time.

Another issue with having the AC fan on all of the time is that you are wearing the fan out that much quicker. We've been there.

[WhiteKitties]

Hmm.... conflicting views here, just as within my family.... Ehh, that's how it always works, right? My house is only three years old, and sealed up relatively tight. The ductwork is not insulated in the basement or in the walls, but there's about a foot of insulation in the attic over everything. We don't have a fan in the attic - I guess new houses don't have them if they have a lot of insulation in the attic, at least not in the Chicagoland area.

Yesterday I ran the air with the fan set to run continuously, and today I set the fan on auto, so it turns on with the air and then runs for about a minute after the compressor turns off. Yesterday the house was basically the same temperature throughout (except for the stairs being hot ) and today there are hot spots and cool spots. The difference is not dramatic, but it's there.

What I had heard from people around here was that running the fan would pull the cool air out of the basement and help keep the house cooler....?

[Mom of 4]

There are two types of "attic fans."
One is intended to keep the attic area cooler by pulling air through the attic from the soffet openings to the eectric fan (or wind turbines).
The second type of attic fan is located on the ceiling inside the house. Leaving windows slightly open, exterior doors (screened) open, the fan pulls air through the house and the moving air cools you off. We use it to keep our attic contents from baking, not expecting it to impact our AC bill.
I've had both in different homes, different climates.

A fan (or fans) inside the house will move the air around and eliminate hot/cold spots in the rooms they occupy.
Leaving the AC/furnance fan on moves air thoughout the entire house, but uses more energy than ceiling fans.

[gunterkat]

It seems my previous post caused some confusion on this thread.
I should clarify.
The fan I used with the air conditioning system in my apartment in Metairie was one that was separate from the a/c unit. It was a small, cheap fan I placed inside the return air space, under the vertically mounted a/c unit, facing upward, behind the return air grill. It created a small positive pressure in the a/c system, which kept a small amount of air blowing out of the ducts when the main a/c blower was off. The continuous small positive pressure in the leaky ductwork was just enough to prevent hot air from inside the utility space from infiltrating into those leaky ducts while the main a/c blower was off.
Thus the substantial utility bill savings.
Before I placed the "supplementary" fan in the return air duct, the a/c would produce a furnace-like blast of hot air from the vents for almost a full minute, every time it kicked on in the summer. In the scorching New Orleans summers that initial hot blast from the a/c could be quite uncomfortable. I complained to the landlord about it many times, but they did not care.
So, by putting on my thinking cap, I got a nice increase in my physical comfort, along with an increase in my financial "comfort level".