box size dimensions for 2inch EMT

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won4thewoad

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I am running 2 inch EMT across the ceilings of some commercial shell buildings . . .where each indivigual conduit goes through the walll into the equipment roomI want to mount a junction box there and then go right angle down to top of electrcial cabinet

so...one 2 inch EMT entering back of J-box on a horizontal plane . .then going 90% straight down into another 2 inch EMT conduit
conductors are 208volt..#2/0 / /three hots and an neutral..with an #4 groundFellas I need your help . .



I have sweated the calculations for try and figure our correct size and dimensions of J-box required . .and I cant seem to understand how to run that calculation properly
can anyone more experienced help me with this

My Thanks in advance Kingsmurf
 
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Whats the bend radius on a 2/0????I don't have any info with me but thats getting up there,an LBNEC comes to mind made by Crouse Hinds. 2 1/2 is the smallest made but I believe the cover opening is about 20" but the bend radius to close the cover is only about 5 " if I remember correctly. It may just take the sq box you talked about entering the side near the top and exiting 90 degrees away
near the far side using the req'd bend radius to size the box.Can you use a long radius elbow?

dick
 
314.71 B 1 exception 1

if you are going in the BACK of the box (as you stated) opposite the cover, you only need to worry about the fill and bending radius of the conducter.
(even though from your post it sounded like you meant you were entering the side of the box)
 
if you are looking for a good book to explain your problem try Mike holts book titled ( electrical nec exam preparation) page 206-209 This forum is a graet place for answers but that book explains everything in great detail
 
won4thewoad said:
I am running 2 inch EMT across the ceilings of some commercial shell buildings . . .where each indivigual conduit goes through the walll into the equipment roomI want to mount a junction box there and then go right angle down to top of electrcial cabinet

so...one 2 inch EMT entering back of J-box on a horizontal plane . .then going 90% straight down into another 2 inch EMT conduit
conductors are 208volt..#2/0 / /three hots and an neutral..with an #4 groundFellas I need your help . .



I have sweated the calculations for try and figure our correct size and dimensions of J-box required . .and I cant seem to understand how to run that calculation properly
can anyone more experienced help me with this

My Thanks in advance Kingsmurf
Click to expand...
Look at 314.28 (A) (2) Exception - it tells you for raceway entry is in the wall opposite a removable cover, that distance must be found using 312.6(A) - one wire per terminal. So, for 2/0 wire, that depth must be at least 3 1/2" from cover to back of box. The dimension required for the box width is found as in 314.28 (A) (2) - distance between each raceway entry inside the box & the opposite wall of the box shall not be less than 6X the largest raceway in that row. Assuming you don't have other conduits on the same wall, the width must be 2" x 6, or 12". That sound to me like a 12" x 3 1/2" box as a minimum. The other dimension size would depend of box fill of the conductors, to make sure you have enough sq inches. It wouldn't hurt to go deeper - say 6" deep- for your own pulling convenience.
 
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nakulak said:
314.71 B 1 exception 1

if you are going in the BACK of the box (as you stated) opposite the cover, you only need to worry about the fill and bending radius of the conducter.
(even though from your post it sounded like you meant you were entering the side of the box)
Click to expand...

314.71 is for over 600V. I think the section that would describe your sentiments would be 314.28(A)(2) Ex, since we are talking about a 208V installation.
 
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