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Thread: 1600 amp wire size calc

  1. #1

    Talking 1600 amp wire size calc

    my question is about sizing conductors for a 1600 amp single phase service.

    would 4 - # 500 MCM copper THWN-2 RATED FOR 90 C per phase be adequate

    the run is less than 6 feet from ct cabinet to service disconnect

    the allowable ampacities chart says 500 mMCM is good for 430 amps x 4 = 1720

    Thanks for any comments

  2. #2
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    Sorry, but no. You can't use the 90C column for ampacity, unless all the components in the circuit are rated for 90C. The one that generally gets you is the terminations. They are seldom rated higher than 75C. So you can only use the 75C ampacity. Reference 110.14(C).

    Thus, four 500's are only good for 4 x 380, or 1520 amps.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  3. #3
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    See above.
    Last edited by chris kennedy; 11-18-09 at 04:06 PM. Reason: Fast Charlie

  4. #4
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    agree, but, to cover all possibilities: when you say "service disconnect" are you referring to one means (1600 amp breaker or bolt-lok switch, etc.) ?
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  5. #5

    Talking

    charlieB

    good answer.

    We are looking into the lug rating (probably 75-c )
    will have to increase conductor size, thankfully it is a very short run
    Why dont manufactures just use 90-c rated lugs ?

    Thanks again for an A++++ answer

  6. #6
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    Quote Originally Posted by electromantoo View Post
    We are looking into the lug rating (probably 75-c )
    The lug itself may actually be rated 90 C, but the equipment (breakers, fused disconnects, etc) it is connected to will not be.


    Why don't manufactures just use 90-c rated lugs ?
    It would be difficult to make a breaker that could handle a 90 C conductor and still not trip early due to heat.

    That said, I agree with the others, you will need 600 copper or a reduction of the over current protection.

  7. #7
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    Quote Originally Posted by electromantoo View Post
    my question is about sizing conductors for a 1600 amp single phase service.
    Is this a common service in other areas? 1600A 240/120 1Ø 3 wire system. That system at that amperage is very uncommon here. (as in I have never seen one).

  8. #8
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    Quote Originally Posted by chris kennedy View Post
    Is this a common service in other areas? 1600A 240/120 1Ø 3 wire system. That system at that amperage is very uncommon here. (as in I have never seen one).
    Same here.

  9. #9
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    maybe you could post a pic of this service ?

  10. #10
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    Quote Originally Posted by chris kennedy View Post
    Is this a common service in other areas? 1600A 240/120 1Ø 3 wire system. That system at that amperage is very uncommon here. (as in I have never seen one).
    The good news is there is one less conductor per phase ( to upsize ).
    Frank Arizona,USA

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