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Thread: Circuit Size

  1. #1
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    Circuit Size

    Doe sthi make sense to have a 3P-20A breaker with 4 #6's and a disconnect switch fused at 15amps? That's wrong I think.
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  2. #2
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    What's the purpose of the disconnect switch? On the surface it doesn't make much sense but we could be missing some details.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    The #6 is above and beyond what the NEC requires for ampacity reasons, unless there is a serious factor like high ambient temperature, or extreme conductor bundling, or both.

    #12 is what the NEC requires for a 20A circuit. The 15A fused disconnect downstream doesn't override this, until you get downstream of it.

    That being said, if you run #6 for voltage drop or any reason unrelated to ampacity, you have to proportionally upsize the EGC. In this case, it means it would be the same size as the rest of the conductors.

  4. #4
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    Quote Originally Posted by Carultch View Post
    That being said, if you run #6 for voltage drop or any reason unrelated to ampacity, you have to proportionally upsize the EGC. In this case, it means it would be the same size as the rest of the conductors.
    Good point the #10 EGC with the #6's is possibly a violation.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  5. #5
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    Quote Originally Posted by Carultch View Post
    The #6 is above and beyond what the NEC requires for ampacity reasons, unless there is a serious factor like high ambient temperature, or extreme conductor bundling, or both.

    #12 is what the NEC requires for a 20A circuit. The 15A fused disconnect downstream doesn't override this, until you get downstream of it.

    That being said, if you run #6 for voltage drop or any reason unrelated to ampacity, you have to proportionally upsize the EGC. In this case, it means it would be the same size as the rest of the conductors.
    Y would you say a #6 is needed if you upsize for voltage drop do you not use 250.122 table to size the egc

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  6. #6
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    Quote Originally Posted by nickelec View Post
    Y would you say a #6 is needed if you upsize for voltage drop do you not use 250.122 table to size the egc

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    Table 250.122 is the general rule. 250.122(B) would apply if upsizing for voltage drop, and it would require 6 AWG EGC in OP's situation if conductors are sized like they are because of voltage drop.

    Put a 60 amp breaker on it and then 10 AWG EGC is fine though.

    Makes sense yet it doesn't, right?
    I live for today, I'm just a day behind.

  7. #7
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    I don't believe the OP provides enough information to derive an accurate response to the question.
    What is the load served?
    Why #6?
    What is the distances involved?

    Otherwise it's all speculation.
    "Just because you're paranoid, doesn't mean they're not out to get you"

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