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

    Feb 18, 2008, 09:47 PM
    Sub panels
    When installing a sub panel in a single family dwelling coming off a main panel do you size your wire as a feeder according to 310.15 (b) (6) or do you size it as a branch circuit?
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #2

    Feb 18, 2008, 10:04 PM
    Depends on location.
    In my area we are allowed to use 310.15(B)(6) for 100A sub-panels. Meaning #2al or #4cu.
    I use #2SER ALL the time for 100A sub-panels.

    And NO, I don't want to get into the argument about whether this is allowed. Our AHJs allow it and that's all I've ever known around here.

    IMO it is common sense. In a residence a 100A sub-panel will have JUST as much load diversity as a main 100A panel, so why should a sub-panel be required to be fed with larger wire?

    Anyway, check with your local AHJ and see what he says.
    Worst case scenario, use a 90A breaker.
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
    Uber Member
    		  
    #3

    Feb 19, 2008, 06:47 AM
    As Stran states, there should be no reason not to use table 310.15 (B) (6), as this tables is for residential services and feeders, and a cable to a subpanel is considered as a feeder.
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