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    Jack2's Avatar
    Jack2 Posts: 1, Reputation: 1
    New Member
    		  
    #1

    Feb 23, 2009, 12:30 PM
    Sub-panel sizing of wire
    Have an existing 100 amp service. Wish to install a 70 amp sub-panel. What size wire should be used? Distance to sub-panel is 45 feet.
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
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    #2

    Feb 23, 2009, 12:50 PM

    #4 will work, #2 will reduce voltage drop.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #3

    Feb 23, 2009, 02:16 PM
    #2 is extreme overkill at only 45'.
    Voltage drop is not even close to an issue at 45', even at full load amperage.

    Why do you need 70A? Using #6cu you can go with 60A and the wire will be much cheaper. If you do go with #4 you can use a 90A feeder breaker, or even 100A in some cases.

    If you must have a 70A breaker then you must use #4cu.
    Stratmando's Avatar
    Stratmando Posts: 11,188, Reputation: 508
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    #4

    Feb 23, 2009, 02:21 PM

    If this was my Shop, I like a little overkill. Plus, I could easily upgrade to a 100 Amp Panel. I have no idea of other losses/lengths involved.
    #4 will work.
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