Ceiling Fans: Do you leave yours on all the time in summer?

[Orchidflower]

Since I was grousing about my electric bill for August, a friend said that she never turns on her ceiling fans if she isn't using that specific room and always turns them off totally if she isn't home. As I understand it, ceiling fans are really cheap to run, but I'd love to hear others input on if it's worth it to leave your ceiling fans on 24/7 in all your rooms--ones you use and ones you don't.

[REWahoo]

Since the movement of air only cools via skin evaporation, I don't leave any ceiling fan running if we aren't in the room. No, they don't use a lot of electricity but running them when the room isn't occupied is wasteful.

[Rich_by_the_Bay]

In our Wisconsin house with high ceilings and cold winters, we would run them on reverse to pull the cold air upward, mix with the warmer air hovering near the ceiling, and basically reducing the layering of different temperature air. There would be no direct breeze at ground level.

It seemed to make the room warmer and more comfortable, or at least that's what the gas company told us.

[WhoDaresWins]

Before I moved into this house, I went to Lowe's and picked out 5 ceiling fans...two big ones for my living room and master bedroom, and 3 smaller ones for two bedrooms and my den. I love them even if many designers on HGTV seem to now think they are tacky and they are the first things to go when they do-over a place.
I only run the fans if I am in the room and when I leave the house for more than an hour, I shut them off. I don't use mine in the winter at all.

[Nords]

We use our 60" Fanzilla to start a chimney-effect updraft against its living room cathedral ceiling, but we only turn it on when the room gets uncomfortably warm-- perhaps for 4-5 hours on the hottest days.

Otherwise we only turn on our other ceiling fans when we're in the room and if we need a cooling breeze.

Part of the issue might be the fan's rotation. People like to have a breeze blowing down on them, so they set the fan to blow air down from the ceiling. However that not only pulls down the hot air from the ceiling (and blows hotter air on them), it also creates an air curtain (similar to store entrances) that interrupts the tradewind cooling blowing across the room through the open windows.

We set our fans to blow the air up against the ceiling so that they don't blow a breeze down on to us. Instead they pull the floor's cooler air up toward the ceiling, push the ceiling's hot air to the corners of the rooms, and help the tradewinds blow it out through the second-floor windows or the doors.

[Rustic23]

I think the general rule is as Wahoo says. It uses evaporation cooling to do its job. However, there may be some advantage to leaving a fan on depending on the rooms structure. i.e. high ceilings.

Now on another side of the equation, a friend told me that his AC man said to leave the AC fan on 'On' rather than auto. That the circulation of air will actually lower you bill. Could be that circulating cool air through the system does not allow that burst of hot air coming through when the system has set idle for a while. Not sure at all on this one.

[Retire2013]

Quote:

Originally Posted by Rustic23 I think the general rule is as Wahoo says. It uses evaporation cooling to do its job. However, there may be some advantage to leaving a fan on depending on the rooms structure. i.e. high ceilings. Now on another side of the equation, a friend told me that his AC man said to leave the AC fan on 'On' rather than auto. That the circulation of air will actually lower you bill. Could be that circulating cool air through the system does not allow that burst of hot air coming through when the system has set idle for a while. Not sure at all on this one.

This is true. I've tried leaving the AC fan ON all the time and the house feels cooler even at a higher temp setting so I did end up saving on my electric bill. Your AC man was right.

[Sarah in SC]

Quote:

Originally Posted by Nords We use our 60" Fanzilla to start a chimney-effect updraft against its living room cathedral ceiling, but we only turn it on when the room gets uncomfortably warm-- perhaps for 4-5 hours on the hottest days. Otherwise we only turn on our other ceiling fans when we're in the room and if we need a cooling breeze. Part of the issue might be the fan's rotation. People like to have a breeze blowing down on them, so they set the fan to blow air down from the ceiling. However that not only pulls down the hot air from the ceiling (and blows hotter air on them), it also creates an air curtain (similar to store entrances) that interrupts the tradewind cooling blowing across the room through the open windows. We set our fans to blow the air up against the ceiling so that they don't blow a breeze down on to us. Instead they pull the floor's cooler air up toward the ceiling, push the ceiling's hot air to the corners of the rooms, and help the tradewinds blow it out through the second-floor windows or the doors.

That really does make a lot of sense to me--thanks for the explanation. I've always been one of those reverse them when the weather changes to blow down in hot and blow up in cold, but I think your concept is quite reasonable.

[Retire2013]

How do I "reverse" the fan?

[REWahoo]

Quote:

Originally Posted by Retire2014 This is true. I've tried leaving the AC fan ON all the time and the house feels cooler even at a higher temp setting so I did end up saving on my electric bill. Your AC man was right.

Be aware that leaving the AC fan on full time will increase the humidity level inside your house. Once the compressor cuts off, air blowing across the coils will transfer the moisture condensed on those coils (think of the moisture condensed on a glass of ice water) into your house. If you live in Arizona this might not be a problem, but it might be uncomfortable in the deep south.

Also, if your A/C unit and ducting are located inside a very hot attic area (like mine), leaving the fan running soon begins to blow not on moist air but moist and warm air into the house.

I say leave it off.

[Sarah in SC]

Quote:

Originally Posted by Retire2014 How do I "reverse" the fan?

Usually there is a switch on the side of the fan body. Just changes the direction of the blades.

[RonBoyd]

I was unsure how to answer the poll: Our fans are thermostatically controlled and are, therefore, automatic whether someone is in the room or not. In any event, I run them in the "reverse" direction during the winter months.

[FUEGO]

I think leaving ceiling fans on constantly just uses up electricity and doesn't do anything besides emit a small amount of heat from the fan motor.

In fact, it may be worse than that. It's been a while since engineering school, thermodynamics and systems analysis and all that, but an off the cuff analysis would suggest that leaving the air still may actually be best for keeping cooling bills to a minimum. Newton's law of cooling states that the rate of heat transfer increases as the difference in temperatures between two surfaces increases. In other words, if you have a hot ceiling or wall up against a hot layer of still air inside your house, then the heat transfer rate from ceiling or wall to air will be less than if you had cool(er) air up against the hot ceiling or wall. With the fan on, you have near perfect mixing of air inside your fanned rooms, hence lowering the average temperature of the air in contact with hot surfaces. Without a fan, you have imperfect mixing of the air, and air near hot surfaces gets hotter. My take is you want to keep the hot air against other hot surfaces to keep the heat transfer rate to a minimum.

And the heat released by multiple fans running is not insignificant. I have never tested the energy consumption of my ceiling fans, but I have tested my little window box fan (the $15 kind from walmart) and it consumes between 65-95 watts depending on whether it is on low or high. I know my big 52" ceiling fans move a lot more air than my box fan, so I assume their energy consumption is similarly high. A lot (all??) of the energy used by the fan will enter the room in the form of heat (either from the motor or from friction). And if you are using 300-600 watts non-stop to keep the fans cranking, you are paying $300-600 a year for the privilege (assuming 11c/kWh electricity) not including the additional electricity required to power the HVAC to compensate for the heat generated by the fans. Of course you aren't cranking the fans in the middle of winter, so the figures will vary based on geographic location. And I'm assuming a house with windows closed using HVAC and not relying on windows to cool and circulate air.

[REWahoo]

Quote:

Originally Posted by Retire2014 How do I "reverse" the fan?

Not all are reversible but many fans have a reverse switch that reverses the direction of the blade spin. Some fans have the ability to mechanically reverse the pitch of the fan blades.

[Sam]

Quote:

Originally Posted by Retire2014 How do I "reverse" the fan?

The black switch will reverve the direction of the fan.

[FUEGO]

Quote:

Originally Posted by REWahoo Be aware that leaving the AC fan on full time will increase the humidity level inside your house. Once the compressor cuts off, air blowing across the coils will transfer the moisture condensed on those coils (think of the moisture condensed on a glass of ice water) into your house. If you live in Arizona this might not be a problem, but it might be uncomfortable in the deep south.

This makes sense. At our recently rented beach house, I couldn't figure out why it felt so humid. I noticed the fan was set to ON and the temperature was low, but it always felt muggy inside even though it was in the 70's or low 80's outside.

[Orchidflower]

Quote:

Originally Posted by WhoDaresWins I love them even if many designers on HGTV seem to now think they are tacky and they are the first things to go when they do-over a place..

What is wrong with those people on HGTV? No ceiling fans, no antiques...
They must all live in modern lofts in NYC I suppose. Well, personally, put me with the un-chic folks...I love ceiling fans (and antiques).

I'm going to put my a/c on "On" for awhile and see what happens. That makes too much sense to me to not try it.

[Rustic23]

In Arizona it will at least keep the dust down.

[WhoDaresWins]

Quote:

Originally Posted by Orchidflower What is wrong with those people on HGTV? No ceiling fans, no antiques... They must all live in modern lofts in NYC I suppose. Well, personally, put me with the un-chic folks...I love ceiling fans (and antiques). I'm going to put my a/c on "On" for awhile and see what happens. That makes too much sense to me to not try it.

Things seem to be "in" or not because if they did not change, retailers would not make money. Right now one sees lots of chandeliers in places like bathrooms and bedrooms and also fabric lamp shades as were formerly used only on table lamps from the 50's and 60's. I hated them at first but now I am getting used seeing to them on TV and do not find them so ugly. Lowe's has started carrying them so they are gaining in popularity. I do a lot of house tours and I can tell you that the truly rich old money do not change anything in their homes after they are built....they keep their old kitchens, appliances, threadbare furniture....If it is good quality and functional, it stays forever.
I like my ceiling fans, oriental rugs and antiques, too.

[73ss454]

I have no choice to leave them on, especially the one in the Master Bedroom. DW leaves it on high all night because of the damn hot flashes and I feel like I'm sleeping under a Helicopter.