Gutter Size

[beanland]

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.



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?

 

[Strife]

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.

View attachment 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.

 

[tom baker]

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.

 

[beanland]

Gutter, Wireway, Box

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.

 

[beanland]

Wireways

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.

 

[texie]

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.

 

[jusme123]

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.

 

[texie]

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.

 

[beanland]

Terminations and Pulling

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.

 

[beanland]

Picture

Picture

Just to help, here is what I am dealing with...

 

[texie]

Just to help, here is what I am dealing with...
View attachment 6870

I think 312.6(A) still applies, but you have to be mindfull of the 20% rule for fill. Let's see what others say.

 

[RUWired]

Bean, in wireways used as pull boxes, only distance between raceways enclosing the same conductors keep the 6X or 8X spaceing apart. The opposite wall dimension is from table 312.6A.

Rick

 

[beanland]

I think you are right

I think you are right

The more I look at this, 376.23(B) only references a portion of 314.28(A)(2) that relates to the distance between entries for the same conductor. So, if I have 3/0 AWG, per table 312.6(A) the wireway needs to have 4" bending space. No matter how many 3/0 enter at any point. The conduit size does not play a role.

Then, the distance between entries for the same conductor need to be 6x or 8x the conduit diameter. This just means i need to space my entries out.

Finally, the fill must not exceed 20% at any point of the wireway.

This means, if I have 13 1.5" conduit entries and 13 exits, each with 2-3/0 wires, the minimum bending space is 4". If I have 26-3/0 wires, the 20% rule forces me to a 6"x6" wireway. And, as long as entries for the same wire are at least 9" apart, I am good.

 

[Strife]

Just to help, here is what I am dealing with...
View attachment 6870

You're good as long as you don't have more than a certain number of CCC's(I believe is 32, or 31) at any cross section.

 

[Strife]

I think 312.6(A) still applies, but you have to be mindfull of the 20% rule for fill. Let's see what others say.

I thought for auxiliary gutter there was a set number of CCC(30 or 32?) at any cross section, and over that wires would have to be derated(basically at 50%???)

 

[texie]

I thought for auxiliary gutter there was a set number of CCC(30 or 32?) at any cross section, and over that wires would have to be derated(basically at 50%???)

Yes, you are right on the derating, but was was talking about fill.