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-   -   How many 500mcm wires for a 1000 amp service (https://www.askmehelpdesk.com/showthread.php?t=497439)

  • Aug 12, 2010, 07:09 AM
    mr480
    How many 500mcm wires for a 1000 amp service
    I have a upgrade from 600amp to 1000amp service there are 2 3" conduits from breaker up to weather heads I am pretty sure I need 3 sets of 500mcm per phase can I change the 3"conduits to 4" and split up the phases in that short distance.
  • Aug 12, 2010, 08:17 AM
    tkrussell
    Your pretty sure?

    All conductors of a system must be run together, either bundled or in a raceway.

    So, all three phase and one neutral of each set must be together.

    If you have more than one set in a raceway, you may need to derate.

    Assuming 4- conductors for a three phase four wire system, 500 MCM copper wire with THHN/THWN insulation, I would have three 3 inch conduit risers.
  • Aug 12, 2010, 12:48 PM
    stanfortyman
    Quote:

    Originally Posted by mr480 View Post
    I have a upgrade from 600amp to 1000amp service there are 2 3" conduits from breaker up to weather heads I am pretty sure I need 3 sets of 500mcm per phase can I change the 3"conduits to 4" and split up the phases in that short distance.

    I agree with TK, you are "pretty sure"? This is something I would think you would want to be certain about BEFORE doing it.
    There is a lot of money at stake if it is done wrong.

    Who is doing this work? You or an electrician?
  • Aug 13, 2010, 07:48 AM
    mr480
    Quote:

    Originally Posted by stanfortyman View Post
    I agree with TK, you are "pretty sure"? This is something I would think you would want to be certain about BEFORE doing it.
    There is a lot of money at stake if it is done wrong.

    Who is doing this work? You or an electrician?

    Pretty sure was a figure of speech just wanted to know about running
    9 500mcm's in 2 4" conduits for a lenghth of 10' from breaker to weatherhead and no there is no nuetrals coming from the power company just 3 phase 480 off of the transformer. I have 3 3" running to the station.I really don't have room in enclosure to add another 3" to the top of the can so I thought about upsizing pipe at the pole only.Waiting on specs from breaker company I may need to change enclosure size so that will fix my problem.
  • Aug 13, 2010, 08:42 AM
    tkrussell
    Will each of the two 4" have 9 - #500 MCM?

    For a 1000 amp you only need 3 sets of 3 - #500 MCM

    Something does not make sense.

    If I am reading you correctly, you have 3 - 3 inch conduits already.

    Perhaps some photos of what you have will help you explain.

    I still do not know what type of insulation the 500 MCM has or will have.
  • Aug 13, 2010, 08:46 AM
    mr480
    Quote:

    Originally Posted by tkrussell View Post
    Will each of the two 4" have 9 - #500 MCM?

    For a 1000 amp you only need 3 sets of 3 - #500 MCM

    Something does not make sense.

    If I am reading you correctly, you have 3 - 3 inch conduits already.

    Perhaps some photos of what you have will help you explain.

    I still do not know what type of insulation the 500 MCM has or will have.

    Thhn insulation existing is 2 3" want to change out to 2 4" because of the room put 9 total 500's in 2 4" conduits.
  • Aug 13, 2010, 08:54 AM
    tkrussell
    How do you plan to split 9 - 500 MCM , which I believe is your 3 sets of three?

    Keep in mind, all three legs of each set must be run together.

    4 inch GRC or PVC Sch 40 can only hold 7 - #500 MCM THHN/THWN.

    Be sure your "thhn" is dual rated as THHN/THWN.

    Also keep in mind, that one you have more than 3 current carrying conductors in a raceway, you need to derate.

    If you use 3 - 3 in rises each for 3 - #500 MCM you do not need to derate.
  • Aug 13, 2010, 09:04 AM
    mr480
    We must be on a different page I know I need 3 of each phase for a 1000amp I know I cannot fit 9 wires in 2 3" conduits you can only put 4 each which leaves 1 left over therfore i will need to add a conduit but do to space I would like to replace existing 3" conduits with 4" and put 5 in one of them and 4 in the other what Ive been asking is will it hurt anything
  • Aug 13, 2010, 09:09 AM
    tkrussell
    In my first post, I addressed this question

    Quote:

    Originally Posted by tkrussell View Post
    All conductors of a system must be run together, either bundled or in a raceway.

    So, all three phase and one neutral of each set must be together.

    You cannot split up the phases.

    You cannot run 5 in one and 4 in the other.

    You may run 6 in one conduit and 3 in the other
    Conduit.

    And, then, if you do run 6 in one conduit, it is more than three current carrying conductors, you must derate the 6 conductors that would be together.
  • Aug 13, 2010, 09:12 AM
    mr480
    Quote:

    Originally Posted by tkrussell View Post
    In my first post, I addressed this question



    You cannot split up the phases.

    You cannot run 5 in one and 4 in the other.

    You may run 6 in one conduit and 3 in the other
    conduit.

    And, then, if you do run 6 in one conduit, it is more than three current carrying conductors, you must derate the 6 conductors that would be together.

    Thanks that is what I was not sure of
  • Aug 13, 2010, 09:13 AM
    tkrussell
    OK, now that I got my point across, can you tell me why phase conductors can not be split up?

    Also, what is your background?
  • Aug 13, 2010, 09:16 AM
    mr480
    Quote:

    Originally Posted by tkrussell View Post
    OK, now that I got my point across, can you tell me why phase conductors can not be split up?

    Also, what is your background?

    Painter
  • Aug 13, 2010, 12:32 PM
    tkrussell
    So I will guess that you do not know why the phase conductors cannot be split.
  • Aug 13, 2010, 03:29 PM
    mr480
    Quote:

    Originally Posted by tkrussell View Post
    So I will guess that you do not know why the phase conductors cannot be split.

    No I don't

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