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According to ehow.com:
In theory, the updraft can aid heating. The premise is that it pulls cool air up to the ceiling, where most of the heated air settles, and then sends warmer air down into the room along the outer walls.
Most fans come with a discreet switch to reverse the direction the motor turns the fan blades.
This is a vertical slide switch with two positions. Generally the down position will cause the fan to blow downward and the up position will create an updraft.
http://www.ehow.com/how_4895488_reverse-ceiling-fan-blades.html
down
Reverse direction of the fan. Move air down in summer of breeze, and up in winter for circulation
up in the summer and down in the winter
Counter Clockwise. Push air down (down position on most fans)
down for the summer and up for winter
With a typical fan, run the fan counter-clockwise in the summer, and in the winter, run the fan clockwise at a low speed. In the summer, blow the air down to directly cool you. If you have a large room, and you are on the outside of the room, you may want to run the fan in the opposite direction. In the winter, blow the air up on slow to pull the cool air up, mixing the cool air with the warm air at the ceiling, and pushing the air across the ceiling to the walls, then coming down the walls, and minimizing wind chill.
In winter, fan should blow down,heat rises,get it back. In summer ,fan should blow up for a 2 story vaulted ceiling,to circulate air but not blow down hot air.On a one story in summer it can blow either,but it's a prefference.Up is ok,but down you get a lower cool index feeling.
For summer use, the airflow should go down directly from the fan to the floor. For winter use it should pull the air from the floor towards the ceiling so it flows across the ceiling and around the room. So as to whether it should be clock-wise or counter clock-wise, that would depend on the angle of your blades. It's best to just stand under it when it's on. In the summer you should feel the air blowing on you from the fan and in the winter you shouldn't.
Paint the ceiling first. Work top down.
The string activates a switch in the fan.
In this way, the shadow of the fan rotating at the floor is clockwise. Ceiling fans can be set up to rotate either way, many of them have a switch that will change the direction. Others can be wired to rotate either way. Typically they are designed to push air rather than pull it.
Three feet from the ceiling will give a good circulation of air from above the fan. Remember in the summer time the fan blows the air down, in the winter time the fan draws the air up.