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Thread: Tandem, or dual, air compressor questions please?

  1. #11
    Join Date
    Jan 2005
    Location
    Buffalo NY
    Posts
    3,762

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    "My start switch contacts are corroded and a replacement is over $40.00 where a relay is much cheaper. "

    You have this large compressor, and you are complaining about spending $40???
    You are trying to retrofit a relay for that kind of current that costs less than $40??
    A large compressor like this is not something to try and cheap out on.
    A motor starter sounds like a good safe solution, but that costs money.
    If you don't want to spend $40 to fix your contacts, you are destined to fail,
    with whatever solution you bodge up.

    -Doozer

  2. #12
    Join Date
    Feb 2010
    Location
    Hampstead, NC
    Posts
    239

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    I don't know. From the research I did it appears that simply feeding voltage through the unused set of contacts allows a 3 ph to work fine in single.

    Galaxy S4, Slimkat
    If I wasn't married I'd quit fishing

  3. #13
    Join Date
    Nov 2007
    Location
    Woodinville, WA
    Posts
    7,992

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    The coil on the contractor is "Single Phase". To interrupt your single phase motor supply you can use any two of the the contact sets BUT they should be listed (UL listed or whatever) for single phase operation at the HP and voltage you use. Look up the manf. data. You might be lucky, or not.
    Last edited by lakeside53; 09-12-2017 at 10:18 PM.

  4. #14
    Join Date
    Feb 2010
    Location
    Hampstead, NC
    Posts
    239

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    I just rechecked the data for the starters I purchased. The overloads on the unit have a range of 15-24 FLA. This will work for the motor.
    I don't hate the idea of buying a replacement switch BUT IF I can get a solid state replacement for substantially less money isn't that a no Brainer? I would think that converting a mechanical switch to a solid state switch is an improvement.

    Galaxy S4, Slimkat
    If I wasn't married I'd quit fishing

  5. #15
    Join Date
    Nov 2007
    Location
    Woodinville, WA
    Posts
    7,992

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    You said in your first post they pull 27-28 amps. Won't that be a problem? Compressors usually run at FLA, or even slighter higher if you have SF motors installed.

    The current trip portion is only one part of the ratings of a motor starter. The contacts need to reliably handle the startup surge. When you get them, look on the body of the contactor - it normally has the various 3 phase (and hopefully) the single phase rating printed on it.
    Last edited by lakeside53; 09-13-2017 at 12:42 AM.

  6. #16
    Join Date
    Feb 2010
    Location
    Hampstead, NC
    Posts
    239

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    That was my mistake. The baldor L141T FLA is 23. The Eaton A27CGD25B024 FL = 25.

    Galaxy S4, Slimkat
    If I wasn't married I'd quit fishing

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