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Thread: Feeder Circuits

  1. #1
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    Cool Feeder Circuits

    I have a know it all electrican who would like to run parallel feeder (600amp)conductors from a 600amp disconnect take one set and feed a 400 amp circuit and another set to feed a 200amp circuit. He is bacically splitting the parallel feeder in luie of setting a 600 distribution panel from the start and installing individual CB's for the loads. Sounds bogus to me.

    Your thoughs would be appreciated.
    Thanks
    Dan Craven

  2. #2
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    Depends on what he does with it before it "splits". If they all combine at some sort of terminal block, at the far end, I'd have no issues with it. Just a feeder tap, at that point. If just part of the set goes to one disco and the other part of the set goes to another, that's a big-time problem.

  3. #3
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    This can be legally done if you follow the appropriate tap rules. The conductors on the load side of the 600 amp disconnect will then be tap conductors not parallel conductors.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

  4. #4
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    Quote Originally Posted by infinity
    This can be legally done if you follow the appropriate tap rules. The conductors on the load side of the 600 amp disconnect will then be tap conductors not parallel conductors.
    Which would make them subect to distance rules. Combine them at the far end too, and you can run them a mile before you tap them if you want to.

  5. #5
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    Quote Originally Posted by mdshunk
    Which would make them subect to distance rules. Combine them at the far end too, and you can run them a mile before you tap them if you want to.

    True, but he did say he wanted to come off the disco with 2 separate sets and feed two different loads. It can legally be done but as you've pointed out there will be distance limits.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

  6. #6
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    Quote Originally Posted by blues
    I have a know it all electrican who would like to run parallel feeder (600amp)conductors from a 600amp disconnect take one set and feed a 400 amp circuit and another set to feed a 200amp circuit. He is bacically splitting the parallel feeder in luie of setting a 600 distribution panel from the start and installing individual CB's for the loads.
    If I'm reading this correctly, he's saying that each of the two feeder sets is capable of the entire 600 amps individually, and that only the supply ends are joined, so they're not paralleled sets.

    As long as they land on OCPD's that are sized for their respective load conductors, he's okay. If I'm right, they're not under-protected, so they're not dependent on tap rules. It's expensive, but okay.

    Now, if the load ends are also joined, they're in parallel, and way protected, so he only has to be concerned with after the split, which I guess will be in a box or trough.

    If he reduces to 400a and 200a conductors that go their own ways, those are taps that are limited, and need to land on appropriate OCPD's within the length limits.

    I hope I know what I'm talking about here.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  7. #7
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    Without distance, wiring method and conductor size, I think this one's impossible to answer correctly. Say it's a 100 foot run. Parallel 350 kcmil copper conductors connected at the supply and tap ends with listed connectors could be tapped to a 400 and a 200 ampere fusible safety switch. If these same conductors aren't connected together at the "tap" end, then we have a serious problem as Marc stated. 240.21(B)

  8. #8
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    Quote Originally Posted by LarryFine
    If I'm reading this correctly, he's saying that each of the two feeder sets is capable of the entire 600 amps individually, and that only the supply ends are joined, so they're not paralleled sets.

    As long as they land on OCPD's that are sized for their respective load conductors, he's okay. If I'm right, they're not under-protected, so they're not dependent on tap rules. It's expensive, but okay.

    Now, if the load ends are also joined, they're in parallel, and way protected, so he only has to be concerned with after the split, which I guess will be in a box or trough.

    If he reduces to 400a and 200a conductors that go their own ways, those are taps that are limited, and need to land on appropriate OCPD's within the length limits.

    I hope I know what I'm talking about here.
    I agree with you.

    The two 600amp conductors are not tap conductors because they are protected by 600amp circuit breaker. The tap rules don't apply for this case.
    David Lin

  9. #9
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    Quote Originally Posted by dahualin
    I agree with you.

    The two 600amp conductors are not tap conductors because they are protected by 600amp circuit breaker. The tap rules don't apply for this case.
    I agree as well, however I very much doubt that is really what is being suggested.

    Conductors are to costly for someone to do it that way.

  10. #10
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    Quote Originally Posted by dahualin
    I agree with you.

    The two 600amp conductors are not tap conductors because they are protected by 600amp circuit breaker. The tap rules don't apply for this case.

    The tap rules could apply if the two feeders are 25' or less and the tap condcutors are 1/3 or larger in ampacity.
    Rob

    Chief Moderator

    All responses based on the 2011 NEC unless otherwise noted

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