junction box calculation mind screw - Contractor Talk - Professional Construction and Remodeling Forum

kingsmurf · 07-21-2008, 08:29 PM

wee . . .trying to fathom the calculator for the Junction box calcs . .
maybe someone can help . . .have 2 inch EMT coming horizontally
through wall into back of ? Junction box..then turning right angle to exit box downward into another 2 inch EMT . . .no splices . .am grounding box . .even though there are no splices

Conductors entering and leaving 208 volt 3PH
3- 0/2 conductors
1-0/2 neutral
1- #4 ground

can anyone tell me the dimensions of the CORRECT
removable cover Junction box?

wow any help here would be of great help

kingsmurf imwithpug@gmail.com

Magnettica · 07-21-2008, 09:21 PM

Your pull box needs to be six-times larger than the size of the largest conduit entering the box. Here, your conduit is 2" EMT so your box needs to be at least 12".

NEC -- 314.28 (A)(2)

Sparky Joe · 07-22-2008, 01:29 AM

You need at least 12" between conduits.

The article mentioned above says the conduits need 6 times their size between them.

A 12" box will work, just be sure to punch the 2 holes as far away from each other as possible.

Magnettica · 07-22-2008, 04:16 PM

Angle or U Pulls. Where splices or where angle or U
pulls are made, the distance between each raceway entry
inside the box and the opposite wall of the box shall not be
less than six times the metric designator (trade size) of the
largest raceway in a row. This distance shall be increased
for additional entries by the amount of the sum of the di-
ameters of all other raceway entries in the same row on the
same wall of the box. Each row shall be calculated indi-
vidually, and the single row that provides the maximum
distance shall be used.

luckyshadow · 07-23-2008, 06:30 PM

article 314.28 A 2
Tells you how to calculate the size of your junction box.
PLUS remember seeing how you are entering through the back of the box be sure to follow the exception of 314.28 (A) (2).
It refers you to 312.6(A) for the depth of the box.
Which for your 2/0 conductors a minimum depth of 3 1/2" is required
Code articles are out of the 2008 NEC