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Determine amps draw of 3PH load on 3PH panel

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    Determine amps draw of 3PH load on 3PH panel

    See attached pic for clarification.... Basically am not sure if you apply the Square root of 3 to a three phase branch circuit same as you apply it to overall panel amps calculation.

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    Thanks

    #2
    Any calculation that involves a three phase system will, at some point, bring the factor of "the square root of 3" into play. Sometimes the trick is know where it goes, and whether you are multiplying or dividing by it. Your equation is correct as written.
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

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      #3
      Maybe obvious, but remember that the resulting amperage that you calculate from that will be the average per phase.
      Ron

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        #4
        I would caution against using the phrase "per phase." It frequently leads to a misunderstanding. If phase A carries 10 amps, and phase B carries 10 amps, and phase C carries 10 amps, that is not "10 amps per phase," and it doesn't result in a "total" of 30 amps. The amps leaving the source on phase A return to the source on phases B and C. It is the same amps.
        Charles E. Beck, P.E., Seattle
        Comments based on 2017 NEC unless otherwise noted.

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          #5
          Originally posted by charlie b View Post
          I would caution against using the phrase "per phase." It frequently leads to a misunderstanding. If phase A carries 10 amps, and phase B carries 10 amps, and phase C carries 10 amps, that is not "10 amps per phase," and it doesn't result in a "total" of 30 amps. The amps leaving the source on phase A return to the source on phases B and C. It is the same amps.
          I agree. I would also caution against omitting power factor. If you do, you get VA, not power.

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