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  1. #1
    Join Date
    May 2004
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    Plattsburgh NY
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    Contactor control voltage

    Question: just replaced a contactor that has a 277v coil. Turns out control voltage in this particular system is 230v. Contactor does pull in. Should I leave the contactor in, or replace contactor, with one that has a 230v coil?

    It's a son of a ***** to get to, that's why I really don't want to.

  2. #2
    Join Date
    Feb 2004
    Location
    British Columbia, Canada
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    530
    It depends on what are the consequences when it fails.
    If it's comfort cooling and people just get cranky, that's one thing but if it's a refrigeration system where product loss is a possibility then you want to man up and do it.

    If the pickup voltage is borderline then any variance in supply power or circuit resistance could cause it to drop out or worse, start chattering, which can take out the compressor, burn up the electrics, scare the owner, etc.

    Personally I would change it. Less guilt in the back of my mind adding to my daily stress.

  3. #3
    Join Date
    May 2004
    Location
    Plattsburgh NY
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    Actually the contactor energizes a fan coil squirl cage blower for air curtain heat at front doors of commercial bldg. no big load on control circuit. Thanks for the feed back. Probably will change the contactor. Probably

  4. #4
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    Nov 2006
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    First, your priority should be to find out why there is a 277 volt coil in that contactor if the supply voltage that the unit receives is 230 volts. Check the label for the unit and see what the unit is designed to take. If the unit is designed for 277 volts and it's wired to a 230 volt feed this is a code violation.

  5. #5
    Join Date
    Jul 2007
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    Mount Airy, MD
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    Quote Originally Posted by timebuilder View Post
    First, your priority should be to find out why there is a 277 volt coil in that contactor if the supply voltage that the unit receives is 230 volts. Check the label for the unit and see what the unit is designed to take. If the unit is designed for 277 volts and it's wired to a 230 volt feed this is a code violation.
    And yet we wonder why a higher voltage motor running on a lower voltage would burn up a contactor?

  6. #6
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    I would be wondering how the unit was installed for the wrong voltage.....

  7. #7
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    May 2004
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    Plattsburgh NY
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    Actually, 480 3 phase comes in to the unit and supplies the electric heaters on L1. L2. L3. Then they take one of the phases ( 277) and run it to a step down transformer and go to 230 to power blower fan and 230 also runs through the controls

  8. #8
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    So they installed an actual neutral conductor with those three 480 phases, correct?

  9. #9
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    Quote Originally Posted by timebuilder View Post
    So they installed an actual neutral conductor with those three 480 phases, correct?
    How else do you get 277?

    Sent from my SCH-I510 using Tapatalk 2

  10. #10
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    Quote Originally Posted by jdblack View Post
    How else do you get 277?

    Sent from my SCH-I510 using Tapatalk 2
    When you have a 480 volt secondary, your phase-to-phase voltage is 480, and your phase to neutral voltage is 277. The neutral point is the center of the Wye secondary.

    So, to get 277, you usually wire your load from a phase leg to neutral.

    I suppose you could have a single phase stepdown transformer that happens to have a 277 volt secondary winding, but I have not seen one. Of course, nearly anything is possible.

    Could we see a schematic of the air curtain?
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  11. #11
    Join Date
    May 2004
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    Plattsburgh NY
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    Yes I did see a white lone neutral wire headed back to the panel. No schematics, it's a 1976 Nesbit fan coil

  12. #12
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    Quote Originally Posted by timebuilder View Post
    When you have a 480 volt secondary, your phase-to-phase voltage is 480, and your phase to neutral voltage is 277. The neutral point is the center of the Wye secondary.

    So, to get 277, you usually wire your load from a phase leg to neutral.

    I suppose you could have a single phase stepdown transformer that happens to have a 277 volt secondary winding, but I have not seen one. Of course, nearly anything is possible.

    Could we see a schematic of the air curtain?
    I appreciate the response and i apologize that my smartelic sarcasm wasnt picked up.

    I was rhetorically asking how you would get 277 from a 480 system without a neutral.

    Sorry time. However you did a great job answering the question.

    Sent from my SCH-I510 using Tapatalk 2

  13. #13
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    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







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