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    Hdtrike's Avatar
    Hdtrike Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Feb 15, 2013, 08:31 PM
    Parallel feeders
    A 3ph 400amp service using 250 al can you use one conduit or two conduits, 8 wires
    Grady White's Avatar
    Grady White Posts: 1,417, Reputation: 59
    Ultra Member
    		  
    #2

    Feb 15, 2013, 09:12 PM
    Not sure but I think each feeder has to be in it's own conduit.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #3

    Feb 16, 2013, 05:15 AM
    Either.
    One reason to use separate conduits is to get around the higher derating factor.

    I must say, someone doing this installation should not be asking this question on a "Home & Garden" DIY message board. I hope you are just asking for curiosity or education purposes, or that you have someone on the job with more experience than you.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #4

    Feb 16, 2013, 05:22 AM
    Also, if this is a wye 3-phase system 250MCM AL is not good for your service. You'll have 4 current carrying conductors in each conduit so you have to derate to 80%.
    You'll need 350's.

    See NEC 310.15(B)(5)
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