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    karmelcopia's Avatar
    karmelcopia Posts: 14, Reputation: 1
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    #1

    Apr 22, 2010, 12:22 PM
    Do I use the calculated load or the main breaker rating to determine voltage drop and
    I am running a feeder to a panel in my outbuilding. Do I use my calculated load or do I use the 100 amp main breaker rating for my voltage drop and feeder sizing calculations?
    Missouri Bound's Avatar
    Missouri Bound Posts: 1,532, Reputation: 94
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    #2

    Apr 22, 2010, 12:39 PM
    The voltage drop calculation is determined by wire size and length of run. How far are you going?
    karmelcopia's Avatar
    karmelcopia Posts: 14, Reputation: 1
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    #3

    Apr 22, 2010, 01:01 PM

    I am running nearly 190 feet to the outbuilding. Planning on a 100 amp double pole main breaker although the calculated load is significantly less.
    karmelcopia's Avatar
    karmelcopia Posts: 14, Reputation: 1
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    #4

    Apr 22, 2010, 01:07 PM

    Do I have to gauge my wire on the calculated load or the 100 breaker rating ,as well as figuring in the voltage drop?
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #5

    Apr 22, 2010, 04:03 PM

    Base your calc's on the feeder breaker.

    As an example, you are allowed a 60 A feeder and a 100 A subpanel main in your outbuilding . That 100A breaker will act as a disconnect.

    The wire size is based on the feeder breaker size and distance.
    Missouri Bound's Avatar
    Missouri Bound Posts: 1,532, Reputation: 94
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    #6

    Apr 22, 2010, 05:34 PM
    Karmalcopia, as Kiss said...
    Here's a calculator you can use if you like.
    Wire Size Calculator
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