Pull box sizing

[bunuelbresson]

Hi,

I have a pull box with 6 x 4" raceways entering from the top and exiting from the back.

Here are my calculations please correct me :

Top to bottom: 6x4"+4" = 28"
Back to front: 6x4" + 4" = 28"

Entry to exit point distance: 6x4" = 24"

So I need a 28" high 28" deep box. Width doesn't matter.

Am I correct?

 

[ptonsparky]

See the exception under 314.28(2)

 

[bunuelbresson]

I don't have the code on me. Can you paste it here?

Thanks

 

[bunuelbresson]

I probably have to add the dimensions of the 5 additional conduits to the calculation :

Top to bottom: 6x4"+4" + 4" + 4" + 4" + 4" = 44" ???
Back to front: 6x4" + 4" + 4" + 4" + 4" + 4" = 44" ???

Entry to exit point distance: 6x4" = 24"

 

[ptonsparky]

Treat it as if it were a conduit body. An LB. Rule changes when you have a cover opposite the hole.

 

[jumper]

I don't have the code on me. Can you paste it here?

Thanks

I think this is it:

Exception: Where a raceway or cable entry is in the wall
of a box or conduit body opposite a removable cover, the
distance from that wall to the cover shall be permitted to
comply with the distance required for one wire per terminal
in Table 312.6(A).

 

[bunuelbresson]

Ptonsparky and Jumper thanks for the reference.

In that case the cables in the conduit are 750Kcmil.

So since the front side (opposite to the Conduit exit point) is removable, then the width of the pull box is as follows:

biggest raceway size + 6 times the diameter of the biggest conductor

4" + 6 x 0.866"= 9.2"

So the box should be :

From top to bottom = 6 x 4" + 4" + 4" + 4" + 4" + 4" = 44"
From back to front = 4" + 6 x 0.866" = 9.2"

Correct?

Thanks

 

[ptonsparky]

Nope not right but I'm turkey hunting so I'm off the clock for a couple days. Maybe someone else will chime in.

 

[electrofelon]

Ptonsparky and Jumper thanks for the reference.

In that case the cables in the conduit are 750Kcmil.

So since the front side (opposite to the Conduit exit point) is removable, then the width of the pull box is as follows:

biggest raceway size + 6 times the diameter of the biggest conductor

4" + 6 x 0.866"= 9.2"

So the box should be :

From top to bottom = 6 x 4" + 4" + 4" + 4" + 4" + 4" = 44"
From back to front = 4" + 6 x 0.866" = 9.2"

Correct?

Thanks

Here is my understanding: because of the exception you ignore everything above the exception. Thus all you have to comply with is the "distance between raceway entries enclosing the same conductor shall not be less than 6 times the trade size of the smaller raceway" which in your case is 24 inches. You could zig zag (not use corresponding entry and exits) to get away with a slightly smaller box if you had to. Oh, and 8 inches deep.

 

[bunuelbresson]

Here is my understanding: because of the exception you ignore everything above the exception. Thus all you have to comply with is the "distance between raceway entries enclosing the same conductor shall not be less than 6 times the trade size of the smaller raceway" which in your case is 24 inches. You could zig zag (not use corresponding entry and exits) to get away with a slightly smaller box if you had to. Oh, and 8 inches deep.

Thank you all for your replies.

Can anyone else confirm electrofelon's statement?

 

[bunuelbresson]

Nope not right but I'm turkey hunting so I'm off the clock for a couple days. Maybe someone else will chime in.

Can you explain why it's not right???

Thanks!

 

[roger]

Can anyone else confirm electrofelon's statement?

Do you have your code book in front of you now?

Roger

 

[augie47]

From my point of view:
Minimum distance to the wall opposite the (6) 4" would be 44" but, as noted, you would have to keep in mind the 6X distance between raceways containing the same conductors.
314.28 refers you to 312,6(A) as to depth taking the removable cover into account and, also as noted, that would be 8".

 

[bunuelbresson]

Do you have your code book in front of you now?

Roger

Yes, the last calculations that I have done are according to my anderstanding of the code clauses. I just don't understand why they are wrong.

Thanks

 

[ptonsparky]

From your description I understand your pull is from one side of the box then out the back. No different than using an LB. You are not doing an angle pull from bottom to left or right side nor are making a U pull of bottom to bottom. Now if you crossed all your raceways and the left bottom needs to go far rt top etc, ...well 44" may not be enough and 8" not near deep enough.

 

[bunuelbresson]

From your description I understand your pull is from one side of the box then out the back. No different than using an LB. You are not doing an angle pull from bottom to left or right side nor are making a U pull of bottom to bottom. Now if you crossed all your raceways and the left bottom needs to go far rt top etc, ...well 44" may not be enough and 8" not near deep enough.

Ptonsparky thanks for your comment,

actually there will be no crossing. But the raceways enter the pannel from the top and exit from the back.



That's what I think the size should be but was told that this is wrong:

From top to bottom it should be : 6 times largest raceway + sum of additional raceways (6 x 4" + 4" + 4" + 4" + 4" + 4")= 44"

From back to front (since the cover is removable): Largest raceway + 6 times the largest conductor (750kcmil - 0.866") = (4" + 6 x 0.866") = 9.196"

So I think it should be 44" tall and 9" deep!
But some forum members disagree.

 

[david luchini]

From back to front (since the cover is removable): Largest raceway + 6 times the largest conductor (750kcmil - 0.866") = (4" + 6 x 0.866") = 9.196"

So I think it should be 44" tall and 9" deep!
But some forum members disagree.

Where are you getting this calculation from?

 

[cpinetree]

Try this calculator : http://www.ite-engineering.com/cgi-bin/pBox.pl

38 x 44 x 8.00 using 1/2" clearance between holes, laid out in a straight line as post #16 shows.

 

[bunuelbresson]

Try this calculator : http://www.ite-engineering.com/cgi-bin/pBox.pl

38 x 44 x 8.00 using 1/2" clearance between holes, laid out in a straight line as post #16 shows.

Thanks. I was looking at the wrong table for the bend radius.

This is clearer now.

Thanks everyone for your inputs. You have been very helpfull.