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    Apartment feeder size question

    I am working on a bid for a multifamily project, 208/120 V where each apartment is served by an SER cable (4-story wood construction bldg).

    Plans call for the following SER sizes (ignoring voltage drop, using AL wiring): 110 Amps 2/0 cable, 125 Amps 3/0 cable and 150 Amps 4/0 cable.

    Since the code eliminated the insulation requirement from article 338 for this size of service cable and since 310.15(B)(7) now allows the factor of 83% to be used for 208/120 I am thinking that this could be done using 2/0 for 150Amps, 1/0 for 125Amps and #1 for 110 Amps.

    What am I missing? Thanks in advance

    #2
    Are you under the 2017 NEC? Earlier versions did not allow the 83% for 208/120 volt systems.
    Rob

    Moderator

    All responses based on the 2017 NEC unless otherwise noted

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      #3
      Yes, we are under 2017 code, thanks

      Comment


        #4
        How about a compromise and use 3-0, 2-0, and 1-0?
        Master Electrician
        Electrical Contractor
        Richmond, VA

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          #5
          I am trying to find out if my code minimums are correct to have a conversation with the owner, i was surprised that the engineer was using wire so much larger. Do you guys agree with my approach or am i missing something?

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            #6
            I wonder if the engineer didn't think you could use the 83% rule or maybe he was using the 60C column as it was in the 2014 nec.
            They say I shot a man named Gray and took his wife to Italy
            She inherited a million bucks and when she died it came to me
            I can't help it if I'm lucky

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