fan control switch keeps burning up

Discussion in 'General Electronics Chat' started by freestyle, Feb 9, 2012.

  1. freestyle

    Thread Starter New Member

    Feb 9, 2012
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    0
    Hello, new member here.

    I ran across this forum and hope someone can help me. I have a 32" Emerson whole-house attic fan, its about 25 years old, can't get parts on it no longer.

    The problem i have is with the variable speed control switch, the original one went out years ago. The fan motor is a (direct drive 6 amp motor with a starting capacitor). I bought one with Grainger, it was 6 amp variable speed fan control, lasted about 5 months it would get very hot till it finally went out. I have been buying the regular 5 amp ones at any hardware store and they last about 2 years then they to get hot an give out, at least they last longer than the Grainger one for a lot cheaper.

    I am trying to find the right controller for this fan, can some one point me in the right direction ? *The fan itself works like a charm, just can't keep controllers to hold up*.
     
  2. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
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    A 6 amp fan controller on a 6 amp motor means it's running at 100% capacity 100% of the time. After verifying the actual fan current, I would get a controller rated a few amps higher.
     
  3. freestyle

    Thread Starter New Member

    Feb 9, 2012
    3
    0
    Thanks for the reply Gerty.


    Can you tell me why just about all controllers say *do not use with starting capacitor driven motors* which is what i have ?
    How does it harm the controller?
     
    Last edited: Feb 11, 2012
  4. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Without seeing what you have I'll take a stab. A capacitor start motor typically has a centrifugal (speed controlled) switch to turn off the start windings/start capacitor, when the motor reaches the proper speed. If you try to control the speed and run it too slowly, the start wings will remain energized.
    What that ends up doing is burning the motor up because it isn't designed to run with both the start and run windings energized. It would probably hurt the controller, because when both start and run windings are energized the motor draws more current than it normally would.
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,053
    3,244
    Perhaps it's a run capacitor that's energized all the time, rather than a start capacitor. In that case there wouldn't be a problem.
     
  6. freestyle

    Thread Starter New Member

    Feb 9, 2012
    3
    0
    Thank you guys for the come back.

    The capacitor is mounted to the frame of the fan not to the motor itself, so i really don't know if its a start or run capacitor. I do know their are other people with the same problem after searching the net for a solution and no one gets a solution. I guess Emerson had a special designed variable speed controller for this application. I did e-mail Emerson support asking for their help, will see if they respond back.

    If memory serves me right the original controller was made with a heat ventilated wall cover, not like the solid state controllers today. Its just a shame i cant find the right controller to fit the fan. :mad:
     
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