Slowing down a fan.

[AOD]

Allright electrical nerds, I've got one for ya.

I have a fan from an old furnace that I want to use to circulate heat from my stove, only problem is it's way overkill! It's a multispeed permanent-split capacitor motor. Even on the lowest speed it is too powerful, and the other fan I have is too wimpy. I;d like a way to have a variable speed control for it, would a normal ceiling fan control work? Could I just add some additional resistance in series with the low speed wire?

 

[Patrick62]

nope

It ain't gonna work. The motor would overheat terribly. The only safe way to reduce the speed of a motor is to reduce the frequency to something less than 60hz....

My recommendation is to find a fan that more closely matches the situation.
One more thing, The extra heat from the wood stove is going to cook the motor, and they don't really like that.

-Pat

 

[valekbrothers]

Hello,

I don't think you want to use a speed control from a ceiling fan. It is not rated heavy enough to run a furnace fan on.
You might want to check out some woodworking places for a speed control for like a router. This should be rated to run something like a fan.

Try www.rockler.com they seem to have just about anything.

Hope this Helps,
Chuck

 

[retired redneck]

I tryed a variable switch on one to slow it down but motor over heated.

 

[AOD]

It ain't gonna work. The motor would overheat terribly. The only safe way to reduce the speed of a motor is to reduce the frequency to something less than 60hz....

My recommendation is to find a fan that more closely matches the situation.
One more thing, The extra heat from the wood stove is going to cook the motor, and they don't really like that.

-Pat

It's an air-cooled, direct drive motor, its always drawing cold room air across it through the cowling. The stove has a jacket around it with a duct outlet, like a small wood furnace, and I intend to push the warm air down a duct. If I tried to choke it down through a 7" duct the velocity would just be screaming, even on low. I would like to use it cuz it was free, but I might have to find something else. The fan thats on the stove now barely moves 300 CFM;s

 

[Crofter]

It will work on brush type motors that are not dependant on the cycle frequency to establish rpm. but not on a synchronous motor. If you drop the voltage it still tries to run the same rpm but it causes a phase shift that causes the heating redneck refers to. A Better choice might be to go to a smaller blade or squirrel cage that will reduce current draw some and throw less air around.

 

[Jkebxjunke]

question.. is the fan part a fan or a squirrel cage?
if its a squirrel cage blower ... why not try to remove some of the fins? like every other one but make sure its even all the way round... you got it for free so it don't owe you anything if it works great if not what are you out really? cause it sounds like its no good to you in its present state....

 

[AOD]

question.. is the fan part a fan or a squirrel cage?
if its a squirrel cage blower ... why not try to remove some of the fins? like every other one but make sure its even all the way round... you got it for free so it don't owe you anything if it works great if not what are you out really? cause it sounds like its no good to you in its present state....

Guess I never thought of that! I know if I restricted the air coming into it it would slow down the airflow but the motor would just be screaming. I dont think a PSC motor is a synchronous motor, otherwise it could not have multiple speeds, and the run capacitor is intended to prevent current from getting too high in the secondary winding. I know there is a way to slow them down, because there are multiple wires for speeds, I just need to make the low speed even lower.