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Thread: Service Neutral Grounded Conductor Ampacity?

  1. #31
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    Quote Originally Posted by Smart $ View Post
    But the mere fact that a 200A neutral isn't necessarily the minimum leads me to believe the 'desired' answer is one of the other three. For the desired answer to be 200A, I think there'd be clues in other questions that the author is pretty darn facitious.

    Anyone have a premise for choosing 160 or 175?
    I guess it comes down to how you interpret the writer's use of "minimum".
    It could be either the smallest number that will satisfy any possible 200A service situation (my first impression) or the smallest number that will work for the combination that allows the smallest possible service neutral for 200A service (your reasonable interpretation).

  2. #32
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    Quote Originally Posted by Smart $ View Post
    But the mere fact that a 200A neutral isn't necessarily the minimum leads me to believe the 'desired' answer is one of the other three. For the desired answer to be 200A, I think there'd be clues in other questions that the author is pretty darn facitious.

    Anyone have a premise for choosing 160 or 175?
    The only thing I can come up with is 83% rule for residences which would allow 175 amps conductors.
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  3. #33
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    Quote Originally Posted by Smart $ View Post
    You need to know the calculated neutral load under 220.61 to reduce the neutral conductor size to less than the ungrounded conductors.
    Isn't that how the guesting needs to be answered since there is no information given . The size would have to be a min of 200 amp

  4. #34
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    Quote Originally Posted by david View Post
    Isn't that how the guesting needs to be answered since there is no information given . The size would have to be a min of 200 amp
    That just it, 200A isn't necessarily the minimum. It is, however, the safest without knowing the calculated load AND the maximum unbalanced calculated neutral load. But not knowing the latter calc is technically a violation in and of itself if one is trying to determine the minimum service neutral conductor size.
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  5. #35
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    Quote Originally Posted by Dennis Alwon View Post
    The only thing I can come up with is 83% rule for residences which would allow 175 amps conductors.
    And this is a legitimate reduction if we knew it was residential!
    I will have achieved my life's goal if I die with a smile on my face.

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