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Thread: Parallel Conductor Question

  1. #11
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    Quote Originally Posted by don_resqcapt19 View Post
    But the wording of 310.10(H)(5) muddies the waters a bit.
    The mere mention of "smaller than 1/0" does, as it infers that another requirement says they cannot be smaller than 1/0 AWG. Yet there is no such requirement for EGC's, sectioned or otherwise.

    Quote Originally Posted by don_resqcapt19 View Post
    ... especially with a number of the CMPs saying that the words "shall be permitted" act to prohibit that that is not specifically permitted.
    Under that premise, sectioned EGC's in multiconductor cables which are 1/0 AWG and larger are not permitted
    I will have achieved my life's goal if I die with a smile on my face.

  2. #12
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    I can't get anywhere with the original post.

    3-250's : Does that mean 1 conductor for each of 3 phases, or 3 conductors per phase?? One is too small, and 3 seems way too big. Even 2 would seem larger than necessary.

    (2) 2.5" conduit: How do I divide one set of conductors into 2 conduits? If part 1 means 3 sets of conductors, again, I can't put three parallel sets into 2 conduits??

    1/0 ground: Given the above confusion, all I can do is guess. Maybe they meant (2) sets of 250KCM for the conductors, and then sized the ground per table 250-66. But it seems like the ground for this should be sized per table 250-122.

    Finally, do we need a neutral conductor for the equipment? Like most bad power specs, they leave you guessing at that one.


    So all in all, I would call this a really bad power spec. to try and learn from.
    Last edited by steve66; 06-05-12 at 01:34 PM.

  3. #13
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    Quote Originally Posted by steve66 View Post
    I can't get anywhere with the original post.

    3-250's : Does that mean 1 conductor for each of 3 phases, or 3 conductors per phase?? One is too small, and 3 seems way too big. Even 2 would seem larger than necessary.
    It means one 250 kcmil per phase per conduit

    (2) 2.5" conduit: How do I divide one set of conductors into 2 conduits? If part 1 means 3 sets of conductors, again, I can't put three parallel sets into 2 conduits??
    That means two 2.5" conduits, each with one 250 kcmil per phase and a 1/0 EGC.

    1/0 ground: Given the above confusion, all I can do is guess. Maybe they meant (2) sets of 250KCM for the conductors, and then sized the ground per table 250-66. But it seems like the ground for this should be sized per table 250-122.
    When you are running parallel conductors in more than one conduit or cable, the EGC in each conduit or cable must be full sized based on the size of the over current protective device and Table 250.122. See 250.122(F). The maximum OCPD for parallel 250's would be 600 (assuming this is not a motor load) and the code required EGC would be a #1 in each raceway. The spec writer may have increased that to a 1/0 based on the parallel conductor rules in Article 310, but in my opinion a #1 in each raceway is code compliant.

    Finally, do we need a neutral conductor for the equipment? Like most bad power specs, they leave you guessing at that one.
    That I cannot answer.
    So all in all, I would call this a really bad power spec. to try and learn from.
    Not really a bad spec.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

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