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Thread: tap rule clarification

  1. #11
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    Quote Originally Posted by ramsy View Post
    Taps are not eligible for next-size up rule. As Kwired notes, 3/0 cu @75c is minimum size for 200A fuse.

    35ft inside industrial building, only in industrial occupancies, where conditions of maintenance
    and supervision ensure that only qualified persons service the equipment.
    Please explain next-size up rule. thanks

  2. #12
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    Quote Originally Posted by hardworker View Post
    Please explain next-size up rule. thanks
    240.4(B).
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #13
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    Quote Originally Posted by hardworker View Post
    Please explain next-size up rule. thanks
    NFPA-70 240.21(B)
    "..provision of 240.4(B) shal NOT be permitted for tap conductors"
    Roger Ramjet NoFixNoPay

  4. #14
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    Quote Originally Posted by infinity View Post
    You could use #2/0 (minimum size is 400/3=133 amps) you would just need to use 175 amp fuses in the disconnect.
    If I go with 175 amp fuses and 2/0 how many feet for the tap?

  5. #15
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    Quote Originally Posted by hardworker View Post
    If I go with 175 amp fuses and 2/0 how many feet for the tap?
    Same as the aforementioned #3/0.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #16
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    Quote Originally Posted by ramsy View Post
    Taps are not eligible for next-size up rule. As Kwired notes, 3/0 cu @75c is minimum size for 200A fuse.

    35ft inside industrial building, only in industrial occupancies, where conditions of maintenance
    and supervision ensure that only qualified persons service the equipment.
    Would you give example of the next-size up rule?

  7. #17
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    Say you're installing a 200 amp feeder to a 200 amp panel using #4/0 XHHW with an ampacity of 180 amps. Calculated load on the panel is 150 amps so you can go up to the next standard size OCPD (200 amps, 180 is not a standard size) from 240.6(A) to protect the feeder.

    So you have 200 amp panel> 150 amp load> 180 amp conductor> 200 amp OCPD, all code compliant.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  8. #18
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    Quote Originally Posted by hardworker View Post
    Would you give example of the next-size up rule?
    Say you have a conductor that has an ampacity of 185A. Since 185A is not a standard size breaker or Fuse you are allowed to use the next largest breaker/fuse which would be 200A. However the load would be limited to 185A.

    ETA: Sorry Rob, I was posting (slowly) while you were!
    If you aim at nothing, you will hit it every time!

  9. #19
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    Quote Originally Posted by hardworker View Post
    Would you give example of the next-size up rule?
    I hope you are not attempting this yourself, without a code book, or a clue?
    Roger Ramjet NoFixNoPay

  10. #20
    Join Date
    Feb 2004
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    I am getting old and my memory is not as good as it use to be. I have a young electrician doing most of the work, but I like to check what he is doing. You guys have a lot of knowledge at your fingertips. Many thanks.

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