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Thread: Seperate neutrals for every circuit?!

  1. #1
    Join Date
    Sep 2008
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    Seperate neutrals for every circuit?!

    Currently doing a job where the engineer is requesting a seperate neutral conductor for each circuit.... he is saying it is because the transformer has a phase displacement... I understand a phase displacement but is there a situation that requires an individual neutral for every single circuit?
    The panels are simply feeding receptacles etc and not specific equipment.
    I tend to believe that from the load side of the Tranny it shouldn't matter. Any help to clarify this would be appreciated.

  2. #2
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    Did the engineer ask for it before or after you gave your price? That is all that matters.

  3. #3
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    Sep 2008
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    IMO this is a typical install for the isolation of harmonics to prevent ground loops in a audio application. On top of that all the circuits pertaining to the audio would also be on the same phase. You then use the remaining phases for "dirty power"

  4. #4
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    Quote Originally Posted by joedirt
    Currently doing a job where the engineer is requesting a seperate neutral conductor for each circuit.

    He can do that if he wishes. I had a client that insisted on that. If the client is willing to pay the extra costs, so be it.
    Quote Originally Posted by joedirt
    he is saying it is because the transformer has a phase displacement.

    That is nonsense. Yes, there will be a phase difference between the primary and secondary voltages. That does not matter, since the loads are connected to the secondary, not to the primary. The phase angle of the load, with respect to the phase angle of the primary, has no relevance to the way the circuits operate, nor to how they need to be wired.
    Quote Originally Posted by joedirt
    I tend to believe that from the load side of the Tranny it shouldn't matter.

    You are correct.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  5. #5
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    It's a solution to computer harmonics on receptacle loads. This is a summary from Mike Holt's book.

    http://www.electrical-contractor.net.../Harmonics.htm

  6. #6
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    he can spec gold plated toilets if the end user wants to pay for them.
    Bob

  7. #7
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    Quote Originally Posted by Mr. Bill
    It's a solution to computer harmonics on receptacle loads. This is a summary from Mike Holt's book.

    I would not call it a solution, the harmonics are still present now you just have to worry about them on the feeder panel and transformer.

  8. #8
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    Sep 2008
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    Well the engineer is requesting it now... after 3 levels are pulled! There is nothing in the specs and the conduits are not sized for that.
    Like I mentioned... I believe that I understand harmonics and I understand how electronic loads are creating the need for larger neutrals. The load side of the Tranny feeding the panel has 200% neutral, but again... I didn't think each circuit would require it's own.

  9. #9
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    Quote Originally Posted by joedirt
    I didn't think each circuit would require it's own.
    NEC wise it is not required, beyond that it is a design decision.

    I would be excited about it, I would price up the extra and turn it in.

  10. #10
    Join Date
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    Quote Originally Posted by joedirt
    Well the engineer is requesting it now... after 3 levels are pulled! There is nothing in the specs and the conduits are not sized for that.
    #1. Do not change anything without a healthy change order in writing and signed! (after you make SURE it's not hidden in the specs somewhere, AND the engineer acknowledges the fact)

    #2. See #1.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

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