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  1. #1
    Join Date
    Aug 2003
    Location
    Charleston,SC
    Posts
    515

    Exhaust fans and speed controls

    This might have been asked in controls but, here goes...Have older roof exhaust fans that seem to be causing negative pressure in several kitchens. Might be asking the age old question...speed control of psc motors. Basic 115 vac psc motors (with 3L belts) and have heard that introducing a "speed controller" will cause over heating and thermal ov/ld to open. Have looked into the new vari-green motor from Greenheck and this seems pretty cool. Any ideas besides the expensive JCI S66 or nimbus? Anybody installed the vari-green yet?

  2. #2
    Join Date
    Apr 2010
    Location
    West Virginia
    Posts
    636
    most likely the make up air is the source of the negative pressure, dirty blower wheel, or loose belts.

    Jim

  3. #3
    Join Date
    Jul 2010
    Location
    Fishersville Va
    Posts
    31
    "older" places might not even have makup air.

    Can't pull out what you don't have.

    It's all a balancing act betwen the proper air flow out, the proper air flow in, while keeping the A/C affected as little as possible.

  4. #4
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,168
    Quote Originally Posted by stryder View Post
    This might have been asked in controls but, here goes...Have older roof exhaust fans that seem to be causing negative pressure in several kitchens. Might be asking the age old question...speed control of psc motors. Basic 115 vac psc motors (with 3L belts) and have heard that introducing a "speed controller" will cause over heating and thermal ov/ld to open. Have looked into the new vari-green motor from Greenheck and this seems pretty cool. Any ideas besides the expensive JCI S66 or nimbus? Anybody installed the vari-green yet?
    if belt drive then change sheaves and install a VP sheave on the motor

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