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Thread: Speed Control on Attic Fan?

  1. #1
    Join Date
    Sep 2002

    Default Speed Control on Attic Fan?

    I recently installed a power attic fan and have discovered the noise made by it can be heard almost everywhere in the house. I'd like to install a speed control (like those used on ceiling fans) to slow the RPMs down a bit. Is this OK to do with an attic fan?
    Thanks in advance for the reply, Gary.

  2. #2


    Attic fans are usually quiet, I dont know why yours would be so noisy. Double check the insallation for noticable rubbing spots and or unusual vibrations, mabye install a vibration damper/mounting pads.
    To answer your question, yes you can add a manual switch to run the fan but you would have to bypass the thermo switch which I am assuming is up near the fan. That thermo turns the fan on when the temperature exceeds a factory setting(usually around 110 deg.) If you didnt bypass this thermo, you could turn your manual switch on and nothing would happen since the thermo wouldnt be triggered yet. Sorry for the mouthful, hope you understand.
    I would be lery of a speed control, heres why, the fan is designed to operate for a short time at high speeds to get the hot air out. If you slowed it down it would run all day.And never get the hot out.

  3. #3


    Mtgets, isn't an attic fan with a motor that is designed to run at full speed. I didn't know that attic fans normally come with a shunted pole style motor. Wouln't a motor designed to run at a given speed [full speed] over heat if you attempted to slow the RPM?

    I too believe he may have a loosely installed fan allowing vibration to create the noise or the fan blade is bent causing the vibration.


  4. #4


    This is why you have the website and not I. Thank you Wg for pointing out my error, When I was talking about the manual swith I was truly talking about a on/off switch which is ok. Then for some reason I never gave thought to the attic fan motor style and proceeded to say why I wouldnt put a speed control on it. My mistake, sorry.

  5. #5
    Join Date
    Sep 2002

    Default thanks

    Thanks for the advise. I checked the fan, and it appears to be tightly installed to the roof. When manually spinning the blade, it appears a couple (there are 5) are not perfectly in alignment with the others. Minor bending should solve the vibration issue. I wish there was a way to slow it down sounds like a small cyclone when running. Thanks again! Gary

  6. #6


    Mtgets, if I remember right you have caught a few facts a time or two in a post that I missed. The more that reply the better, more complete, and accurate the information the person seeking knowledge gets.

    grhmerl, also look to make sure the exhaust of this fan has a free unobstructed outlet of air flow. Often times a fan is restricted in input or output causing excessive noise. Like MTgets said, attic fans are usually quite.

    Just a thought


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