Sizing a pull box.

[Robert8020]

This might seem elementary to most... I am sizing a pull box: 12 conduit 4" entering the back of a box, the side opposite the removable cover, and exiting the box bottom. Am I code compliant to use a 48" x 48" x 24" deep pull box?

Thanks
Bob

 

[Dennis Alwon]

See if this helps

 

[augie47]

Welcome to the Forum.
314.28 is you Code guide here.
Your depth is obviously far more than required as far as wire pull as Dennis shows above.
The height of the box would depend on some factors you did not provide. You could not get (12) 4" conduits side by side in a 48" box so there must be more than one row. The opposite wall would need to be 6 X your 4" PLUS the sum of other conduits in the same row, so it depends on the number of conduits per row.
If you have two rows of 6, your 48 would be sufficient. { (6 x 4) + (5 x 4) } but also keep in mind that conduits containing the same conductors must be 6 X their diameter apart.

 

[Robert8020]

Thanks

Thanks

Thank you both for your help. Augie47 you are probably right about the depth. My thinking was ... I have two rows of six conduit entering the back side up high, and two rows exiting as far forward out the bottom, keeping eight inches separation for the heat calcs; that puts my constraint at the distance between the lower row entering the back and the back row exiting the bottom. My first thought was to use an eighteen inch deep box. Doing so would give me nine inches from center of the bottom conduit and the back wall. If I used 312.6a correctly I should need eight inches minimum. If I used the closest edge of the four inch conduit and not the center of it I would be less than eight inches, so that was why I did opt for the 24. Is this thinking in error?

 

[augie47]

312.6(a) does not take conduits into account in any manner. It simply states that with a removable cover your dimension will be "X" (depending on wire size). That number would be your minimum.
The needed depth would obviously also depend on your conduit layout.

 

[Robert8020]

312.6a

312.6a

312.6(a) does not take conduits into account in any manner. It simply states that with a removable cover your dimension will be "X" (depending on wire size). That number would be your minimum.
The needed depth would obviously also depend on your conduit layout.

Yes of course thanks, I failed to mention I am using 600kcmil and according to the 1 wire per terminal I got my eight inch. I assumed this is to keep one from exceeding the bend radius of the conductor. That might be where I am wrong. I was applying the eight inches to my wire bend radius and not to the box depth.

And I was applying the six times distance to a diagonal between the two conduits housing the same conductors.

sorry if I come off as the junior, but
that I am.

Bob

 

[augie47]

Both items you mentioned play a part in selecting your j box. As with most things it's not a simple as one might think.
(The 'junior' automatically disappears after a few more posts )