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Thread: Sizing wireway

  1. #1
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    Sizing wireway

    So I have 8 #250 in (2) 2 1/2” I need a wireway plus I need to splice In the wireway I’m also going from 250 aluminum to 3/0 copper just trying to understand this better

  2. #2
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    I'd go with 6x6x3

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    Quote Originally Posted by vortiz.08 View Post
    So I have 8 #250 in (2) 2 1/2” I need a wireway plus I need to splice In the wireway I’m also going from 250 aluminum to 3/0 copper just trying to understand this better
    You would use art. 376.23 and 314.28 to size it. Wires larger than #4 require the 6 or 8 multiplier based on conduit size. You multiply your largest conduit size by 6 or 8 depending straight or angled pulls, then add all of your other conduits (2.5x8=20+2.5 =22.5). So one of the dimensions of your wireway would have to be greater than or equal to 22.5"

  4. #4
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    There is no need to add the extra conduit sizes on a straight pull. It's simply 8X the largest conduit size.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  5. #5
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    But I will have splices in this how do I calculate that

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    Quote Originally Posted by vortiz.08 View Post
    But I will have splices in this how do I calculate that
    Splices only require 6X in the code rules, but in my opinion for what you are doing even 8X is not enough. What method are you using to make the splices?
    Don, Illinois
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    (All code citations are 2017 unless otherwise noted)

  7. #7
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    Quote Originally Posted by vortiz.08 View Post
    But I will have splices in this how do I calculate that
    May be wrong here but you don't need to calculate for splices. Using the multiplier (6 or 8) times the largest conduit will take this into account. Box fill is only used with conductors smaller that #4

  8. #8
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    Quote Originally Posted by MattS87 View Post
    May be wrong here but you don't need to calculate for splices. Using the multiplier (6 or 8) times the largest conduit will take this into account. Box fill is only used with conductors smaller that #4
    376.22(A) says 20 percent fill for the contained conductors

    376.56(A) says the conductors and splices can't fill any cross section more then 75 percent. So the splicing method will make some difference - though staggering splices so they are not all at same cross section will help with that.
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  9. #9
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    Quote Originally Posted by kwired View Post
    376.22(A) says 20 percent fill for the contained conductors

    376.56(A) says the conductors and splices can't fill any cross section more then 75 percent. So the splicing method will make some difference - though staggering splices so they are not all at same cross section will help with that.
    Good to know. So per the OP's question, how would you calculate how much fill the splices take up? Based on splice method?

  10. #10
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    Quote Originally Posted by MattS87 View Post
    Good to know. So per the OP's question, how would you calculate how much fill the splices take up? Based on splice method?
    Absolutely based on splice method. Crimped butt splice type devices typically won't take up as much room as Polaris connectors or similar.

    conductor fill probably isn't too much issue, especially if entering with raceways at the "ends", as the wireway has to be larger then the raceway(s) just to terminate into the wireway. If running 2 -2.5 inch raceways into an end - you probably need at least 8 inch by 4 inch wireway - presuming that is something available 8x8 is probably something more common though and would have quite a bit of room for splicing - still may want to stagger splices to some extent especially with terminal blocks or polaris connectors.
    I live for today, I'm just a day behind.

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