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Thread: correct method tapping from 3phase main

  1. #1

    Post correct method tapping from 3phase main

    what is the correct method for tapping a 208y/120v 3 phase meter center to feed a single phase 240/120 panel? Can someone point me to the correct code section or provide an answer?

    Thank you

  2. #2
    Join Date
    Dec 2005
    Location
    New York
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    143
    I don't think you will find anything in the NEC. Why not use three phase if it's available. The initial cost may be a little higher, but it's worth it. Also, the main 3 phase panel, most likely, would not be balanced.

  3. #3
    Join Date
    May 2003
    Location
    Maryland
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    Does your equipment require 240-volts? If so you will need a step-up transformer in order to provide it.

  4. #4

    Post continued

    No, the equipment only requires 120 volt.

    Another question: what im feeding is a DP located on the roof of a building. I need to install a new service meter fed from the building multi-meter center. The new meter needs to be separate so its getting mounted adjacent to the existing center. The new panel on the roof is going to be a 200 amp panel with a 200 amp main breaker. What is the recommendation for the new meter? Should it just be a meter/disconnect or should it also contain a 200 amp breaker?

    Thanks

  5. #5
    Join Date
    May 2005
    Location
    Richmond, Virginia
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    21,838
    Electrically speaking, you merely connect to two of the lines and the neutral. Keep in mind, though, that you'll have 120v line-to-neutral and 208v line-to-line, so make sure that any 240v loads will work on 208v.

    Now seeing your second post, stating only 120v loads, I agree that a 3-phase panel would be better, requiring a smaller-sized feeder for the same Kva capacity, except with one more conductor, of course.

    As long as you're outdoors (the entire feeder, that is), you don't have to place the disconnect at any particular point. If I'm not mistaken, the main disconnect can be the one in the roof-top panel.


    Uh, what's a DP? :-?
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  6. #6
    Join Date
    Jan 2005
    Location
    Spotsylvania, VA
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    1,149
    DP=Distribution Panel......possibly?

  7. #7

    Post continued

    DP for distribution panel- Ill use MDP for main distribution panel referring to the panel on the roof.

    Thanks Larry,

    Im required by building owner to put the meter in the meter room located indoors, 4 floors down. My first instinct is to put a meter/disconnect in the meter room and only have a single 200 amp breaker at the MDP on the roof so i can avoid any coordination issues. any issues with that?

    That said, mounting the meter next to the service, wouldnt i have to maintain the 10 ft tap rule? or would that not apply and why?
    Ron

    Electrical Engineer - Connecticut

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