Pullbox Sizing Question

[finhead]

Nine 3-inch conduits enter the rear of a pullbox (the side opposite the cover) in a 3 x 3 configuration. The conduits leave the bottom of the pull box in two rows. (A row of five toward the rear of the box and a row of four closer to the cover.) All conduits contain 3-500 kcmil conductors.
What is the minimum dimensions for this box?
Thanks for the help.
Brian Dolan

 

[jwelectric]

Re: Pullbox Sizing Question

314.28(A)(2) Exception: for 600 volts and less and 314.71(A)(2)Exception: for over 600 volts

 

[ryan_618]

Re: Pullbox Sizing Question

Probably smaller than you think

 

[don_resqcapt19]

Re: Pullbox Sizing Question

Assuming that the space between conduits is 1.5" and space to wall from conduit is 1", it looks like the code would permit a box that is 32.5"H, 25.5"W and 10.5"D. I'm not sure I would want to try to put all of that wire into that small of a box.
Don

 

[Wes G]

Re: Pullbox Sizing Question

Originally posted by don_resqcapt19:
Assuming that the space between conduits is 1.5" and space to wall from conduit is 1", it looks like the code would permit a box that is 32.5"H, 25.5"W and 10.5"D. I'm not sure I would want to try to put all of that wire into that small of a box.
Don

That's a good point Don. Just because the code allows a certain minimum doesn't make it a good or appropriate installation.
My minimum allowed actually is a bit smaller than yours. Figuring a 3" bushing at 4" OD and minimum space to tighten locknuts or bushings as 1/4" per side I come up with 4 1/2" per conduit, or 13.5 X 13.5" for the 3X3 portion at the back of the box. Add 6 X 3 for the distance between raceways and you come up with 31.5" for the length. Using 4 1/2" X 5 for the longest bottom row = 22.5 for the width. Min. depth per 312.6 is 5" but to get 2 rows of 3" conduit into it would take 9".
So, 31.5 X 22.5 X 9