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Thread: Gutter Size

  1. #1
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    Gutter Size

    NEC 314.28 (B) (2) for angle pulls in a gutter requires 6 times the largest conduit plus the sum of the remaining conduits in the same row for the space across from the conduit entry. I have seven 1.25" EMT in a row which would calculate to 15".

    But, I found the sketch from Mike Holt showing a conduit entry with (what looks like) five 500kcmil conductors and 6" tall wireway. Per my conduit sizing, that whould be a 3" conduit which would require an 18" wireway.

    Click image for larger version. 

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    Does anyone know how Mike was able to reduce the wireway to 6"?

    For my case above, is there a rule that permits a smaller wireway height?
    e^(i pi) = -1

  2. #2
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    Quote Originally Posted by beanland View Post
    NEC 314.28 (B) (2) for angle pulls in a gutter requires 6 times the largest conduit plus the sum of the remaining conduits in the same row for the space across from the conduit entry. I have seven 1.25" EMT in a row which would calculate to 15".

    But, I found the sketch from Mike Holt showing a conduit entry with (what looks like) five 500kcmil conductors and 6" tall wireway. Per my conduit sizing, that whould be a 3" conduit which would require an 18" wireway.

    Click image for larger version. 

Name:	807ecmCBfig3.jpg 
Views:	1158 
Size:	34.9 KB 
ID:	6869

    Does anyone know how Mike was able to reduce the wireway to 6"?

    For my case above, is there a rule that permits a smaller wireway height?
    Yeah,
    You're confusing pull boxes with auxiliary gutters.
    A pull box is assumed to be more or less square(I know they make custom sizes, but then it'd be a gutter ? wouldn't it?. But the standard pull boxes are square.
    In a pull box the problem is not making the first bend, it's about making the second one. if I really use the pull box as a pull box on a straight run(meaning I set up at the pull box, I pull one side, then pull the other), I need to have room to leave the slack in there, as I'll never be able to pull it completely through. In a gutter, the long distance allows me plenty.

  3. #3
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    Also there is a difference and different articles for Gutters and Wireways. A gutter is used at meters and switchboards. A wireway is the more common of the two.
    Moderator-Washington State
    Ancora Imparo

  4. #4
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    Gutter, Wireway, Box

    I agree there is a difference, however, 366.58(B) on gutters refers to 314.28(A) for boxes and uses the same size requirements. There is an exemption for boxes listed and permanently marked (314.28(C)). But, I can't see how to avoid the requirement for the dimension to be per 314.28(A)(2) for angle (offset) pulls in gutters.
    e^(i pi) = -1

  5. #5
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    Wireways

    Wireways 376.23(B) refers to 314.28 also. So, whether it is a "box", "gutter" or "wireway" the size must be per 314.28.
    e^(i pi) = -1

  6. #6
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    You use Table 312.6(A), 1 wire per terminal column. I'd have to look up what exactly directs you there for this. Maybe others can beat me to it.

  7. #7
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    put all seven- 1/14" conduits in a 6x6 trough and your to code, unless your using it as a pull box, than 376.23(B) is the determining factor.

  8. #8
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    Quote Originally Posted by texie View Post
    You use Table 312.6(A), 1 wire per terminal column. I'd have to look up what exactly directs you there for this. Maybe others can beat me to it.
    Duh...It's right there in the OP's graphic 376.23(A) directs you to 312.6(A). These are different rules than for a art 314 JBox.

  9. #9
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    Terminations and Pulling

    OK, 312.6 applies based on wire size. But, I have 14 3/0 conductors pulling through this wireway. None are landing on any terminals. They come in one conduit and go out a different one. The tables in 312.6 apply to landing wires on terminals. And, this is really an article 376 wireway, not a cabinet or equipment enclosure.

    The graphic from Mike Holt showed wires entiering a wireway from a conduit/nipple and disappearing off the side of the image. Doesn't that make it a wireway? If the wires go several feet in the wireway and land on a terminal block, isn't it the space at the terminal block that 312.6 applies to, not the wire pulling clearance at the conduit entry.

    376.23(B) still requires sizing based on the number and size of conduits per 314.28(A). I don't see how I can avoid it.

    I got called on this by a plan checker so am sensitive to 376.23(B), 314.28(A), etc.

    Also, all my wires are larger than #4 AWG so that forces me to size the wireway. If the wires are smaller, then fill becomes the limiting factor.
    e^(i pi) = -1

  10. #10
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    Picture

    Just to help, here is what I am dealing with...
    Click image for larger version. 

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    e^(i pi) = -1

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