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Thread: single to parallel conductors

  1. #1
    Join Date
    May 2011
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    14

    single to parallel conductors

    I was having a discussion with one of my electricians the other day and we came across something i have never seen done, but cant see why it couldnt be done.

    existing condition (1) 3" GRC with (3) 500mcm conductors (1) 1/0 ground conductor. we disconnected the 3" conduit from the existing roof top AHU it was going to and run it into a J-box. due to conductor length we spliced the 500mcm in the J-box and run it to a new AHU. my electrician complained about the small bending space in the AHU and said how it would have been nice to have had smaller conductors to work with.
    so my question would be: is there are code problem if we would have spliced parallel 3/0 in place of the 500mcm leading from the J-box to the new AHU? I wasnt aware of a vilation to the NEC for doing this, but thought it would be a good question.

  2. #2
    Join Date
    Jul 2005
    Location
    Tennessee
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    The only problem you might encounter is derating. For example, in your situation, you might be changing from (3) 500 kcmils in the conduit with an amapcity of 430 amps (90°) to (6) 3/0s with an adjusted ampacity of 360 amps (90°) due to there now being 6 wires in the conduit.
    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.

  3. #3
    Join Date
    May 2011
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    Derating is where the discussion turned to in my office, but if i was going to intentionally run parallel 3/0 i would use 2". this would overall be a cost savings over the use of a single run of 500mcm in a 3" pipe

  4. #4
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    Apr 2004
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    Camarillo, CA
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    How would you splice the two 3/0's to a single 500MCM?

  5. #5
    Join Date
    May 2011
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    14
    the simple way would be a polaris tap that was rated for that. (Insulated mechalical lug)

  6. #6
    Join Date
    Jul 2005
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    Tennessee
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    If you use two conduits for your 3/0s there should be no problem.
    The ground would have to be in each and you would need to meet the 314.28 requirements.
    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.

  7. #7
    Join Date
    Apr 2004
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    Camarillo, CA
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    562
    Quote Originally Posted by tgreen View Post
    the simple way would be a polaris tap that was rated for that. (Insulated mechalical lug)
    I guess that would work. When I hear splice for conductors that large I think compression barrel and and a heat shrink insulating sleeve.

  8. #8
    Join Date
    Feb 2003
    Location
    Massachusetts
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    47,001
    Quote Originally Posted by eric9822 View Post
    I guess that would work. When I hear splice for conductors that large I think compression barrel and and a heat shrink insulating sleeve.
    Those are great but as you can see they will not let you do odd ball things.

    I had to tap a 1600 amp feeder of four 600s with a 800 amp tap of two 600s and a 400 amp tap of one 600.

    I had to get seven port Polaris terminals





  9. #9
    Join Date
    Feb 2009
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    Durango, CO
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    Quote Originally Posted by iwire View Post

    I had to get seven port Polaris terminals
    Love the Polaris. What did those cost? If the line is $120 I'll take the over.
    If Billy Idol or John Denver is on your Ipod go and re-evaluate your life.

  10. #10
    Join Date
    Feb 2003
    Location
    N.C.
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    15,065
    Another option if there is room in the J box is Power Distribution Blocks.


    Roger
    Moderator

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