"trader_4" wrote in message
...
I understand your thinking, but all the power a fan is using in a closed
up

room is going to generating heat.



Part of the power to turn the motor is being used in the wiring, part
is

lost in the bearings of the motor, and whatever is left over is moving
the

air. When the air is moving, that movement is being converted back to
heat.



If it was being used to blow air out of the room, then much of the enegry

used to move the air would be dissapated as heat outside the room.



OK, I agree with your analysis. As long as the air stays within
the room, then the increased energy of the air that the motor transfers to
it has to go somewhere and I agree it would result as heat in the room.
From what I can see, these fans are typically ~75W. From a heat
standpoint,
just pushing the hot air from the ceiling down is going to have a bigger
effect than the 75W ever will. For example, when I turn one of my fans
on I can feel the hotter air moving down suddenly. Once it evens out,
the breeze makes the room feel more comfortable. But from an energy
standpoint, I would bet that the fan constantly moving hot air from higher
levels instead of just leaving it be, raises the temp of the lower levels
of the room a couple orders of magnitude more than the 75W of the fan
generated heat. You also have to wonder on it's effect of using more
AC. Two scenarios. One is leave the air stratified, so the hottest air
is up high where no one is. Or use the fan to bring the hot air down,
where the AC has to deal with it. I guess if you leave the AC slightly
higher because you now have a breeze, it could make up for it. Otherwise,
with the hot air being pushed down, I'd expect the AC is going to have to
run more.


I guess that it could also be the humidity of the air and how the fan blows
the sweat off of your skin that makes you feel cool. With no air movement
and high humidity the room has to be cooler to feel comfortable. Most of
the time it is not the actual temperature, but a combination of many things
that makes you feel cool or hot.

Often if the air conditioner is sized correctly, it will run and keep the
humidity low and then with a small ammount of air blowing across you, you
will feel cool at a higher temperature.

At one time I worked at a hopspital and some people in a room were
complaining about it being hot. Two older ladies were visiting a man that
was out of it. They were hot and I dropped down the lid of the air handler
in the room , took out a wrench and screwdriver and made some noise. They
said it felt cooler already. Told them if they got too cool to turn up the
thermostat.