ARTICLE 314.28 SIZING J BOX

[Greenboy]

I am running 3" EMT ((4)400 MCM + (1) 4/O THWN) X 5 parallel runs to feed a 1,600 amp gear. I am required to install a pull box with an angle pull. Article 314.28 (A2) says, "the distance between each raceway inside the box or conduit body and the opposite wall of the box or conduit body shall not be less that six times the trade size of the largest raceway in a row.

This tells me that 6X3" => I need to be 18" from opening to opening of my 3" conduits.

Now, if I upsize the conduit to 4" for easier pull, with the same size conductors, does the code allow me to use the 3" X 6 => spacing my 4" conduit from opening to opening @ 18"? Is there such exemption and/or latitude? Maybe I need to look at wire bending space?

Thanks in advance

 

[Dennis Alwon]

It does not matter what size wire you use. The pull box is based on conduit size.

 

[Dennis Alwon]

Here is a good illustration-- I think your calc is not correct

 

[iwire]

Now, if I upsize the conduit to 4" for easier pull, with the same size conductors, does the code allow me to use the 3" X 6 => spacing my 4" conduit from opening to opening @ 18"? Is there such exemption and/or latitude?

No.

You do not get to base the spacing on the minimum allowable conduit size, you must base the spacing on what you run.

I see the logic in what you are suggesting but I don't see it as NEC compliant. It might be worth running it by the inspector / AHJ to see what they think.

 

[Greenboy]

Here is a good illustration-- I think your calc is not correct

At the end of the 314.28A(2) states,"The distance between raceway entries enclosing the same conductor shall not be less than six times the trade size of the largest raceway." Thats where I get the 3" X 6, from opening to opening.

 

[Dennis Alwon]

At the end of the 314.28A(2) states,"The distance between raceway entries enclosing the same conductor shall not be less than six times the trade size of the largest raceway." Thats where I get the 3" X 6, from opening to opening.

Yes, I thought you were saying the box must be 18 x 18... my bad.. The `18" is the distance between raceways containing the same conductors... :thumbsup:

The distance between raceway entries enclosing the
same conductor shall not be less than six times the metric
designator (trade size) of the larger raceway.

 

[infinity]

Here is a good illustration-- I think your calc is not correct

I dislike this graphic for one the calculated dimensions are both 20" yet the box is not square, also doesn't the distance between the 2-2" raceways needs to be a minimum of 12" which this graphic does not show?

 

[jumper]

I dislike this graphic for one the calculated dimensions are both 20" yet the box is not square, also doesn't the distance between the 2-2" raceways needs to be a minimum of 12" which this graphic does not show?

If I am correct even worse is the distance between the 3" conduits. 6" X 3" = 18" plus a 3" conduit, 20" ain't gonna make it.

This is what I am referring to:

View attachment 16571

 

[Dennis Alwon]

I dislike this graphic for one the calculated dimensions are both 20" yet the box is not square, also doesn't the distance between the 2-2" raceways needs to be a minimum of 12" which this graphic does not show?

Correct this grahic does not show the distance between the conduits. One has to assume the distance is 12" for the 2" conduit and 18" for the 3" conduit.

 

[Dennis Alwon]

If I am correct even worse is the distance between the 3" conduits. 6" X 3" = 18" plus a 3" conduit, 20" ain't gonna make it.

This is what I am referring to:

View attachment 16571

I don't follow. The distance between the raceways is just the conduit size time 6. You do not add anything. The box would need to be 6x3+2= 20 but you may still need a bigger box to get the 18". At an angle it is probably possible

 

[Jim1959]

I am running 3" EMT ((4)400 MCM + (1) 4/O THWN) X 5 parallel runs to feed a 1,600 amp gear. I am required to install a pull box with an angle pull. Article 314.28 (A2) says, "the distance between each raceway inside the box or conduit body and the opposite wall of the box or conduit body shall not be less that six times the trade size of the largest raceway in a row.

This tells me that 6X3" => I need to be 18" from opening to opening of my 3" conduits.

Now, if I upsize the conduit to 4" for easier pull, with the same size conductors, does the code allow me to use the 3" X 6 => spacing my 4" conduit from opening to opening @ 18"? Is there such exemption and/or latitude? Maybe I need to look at wire bending space?

Thanks in advance

Are the conduits entering adjacent sides of the box, like in the diagram, or in one side and out the back? For five runs, it's going to be tricky entering adjacent sides to get the required dimension for all 5 conduits. I'm hoping you're going out the back, and considering the code is the minimum requirements, I would do myself a favor and increase the box to 36" x 36" 12" or so. Would probably pay off in the easier wire pull.

 

[Greenboy]

Are the conduits entering adjacent sides of the box, like in the diagram, or in one side and out the back? For five runs, it's going to be tricky entering adjacent sides to get the required dimension for all 5 conduits. I'm hoping you're going out the back, and considering the code is the minimum requirements, I would do myself a favor and increase the box to 36" x 36" 12" or so. Would probably pay off in the easier wire pull.

I am entering left side, and exiting the back. 36" by 36" will not work in my case. I will not get the distance required between the first conduits. In order for this to work, I am looking at 48" X 54" X 12" deep.

Am I missing anything? Can I use a 36" X 36"X 12"?View attachment custom j box 2.pdf

 

[Jim1959]

I am entering left side, and exiting the back. 36" by 36" will not work in my case. I will not get the distance required between the first conduits. In order for this to work, I am looking at 48" X 54" X 12" deep.

Am I missing anything? Can I use a 36" X 36"X 12"?View attachment 16573

Now I understand the situation, vertical conduits transitioning to horizontal. Looks like you are on track as long as the enclosure is UL listed.