Junction Box Sizing

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racerdave3

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Western Massachusetts
Hi folks, I have a question about junction box sizing. I have a job where I have underground conduit (1 1/2" PVC) going out to a gargage, and where it comes into the house, I am going to land a junction box and then run SER cable (3 conductor with ground) back to the main service panel. My question deals with the size of the box I will need. I know I have looked in the code book and 314.16 (A) and (B) deal with standard size boxes and conductors as large as #6. Further on in 314.28 they talk about junction box sizing and by the information in this article, it would appear that I would need a box that is 6 times the largest conduit, in this case being 1 1/2", meaning the box would need to be 9" inches, thus a 10 x 10 would work. Am I missing anything here? Also, if the 10 x 10 is the box required by code, what about depth? Is 4 inch ok or more needed? I will of course be splicing the conductors in this box, using connectors suitable for cu/al that keep the conductor separate, NO SPLIT BOLTS in this application. I do have limited space in the area of the basement where this box will be, so I am trying to keep the box as small as I can and stay code compliant. Thank you.
 
Pipe size can not be larger than box depth, so you should be good. Go in on one corner, out on an other furthest away.
 
I guess I'm really looking to see what the thoughts are on a smaller box size. It does seem funny that the code has specific fill guidelines and cubic inch measurements for the smaller boxes and conductors up to #6, but nothing beyond that. Also since I will be having the 4 splices in this box, that will play into it as well. I was eyeballing a 6x6x4 that I have on the shelf, but not sure about it.
 
racerdave3 said:
I guess I'm really looking to see what the thoughts are on a smaller box size. It does seem funny that the code has specific fill guidelines and cubic inch measurements for the smaller boxes and conductors up to #6, but nothing beyond that.
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Actually the code does go beyond that but it is done based on the raceway sizes and if there are no raceways it is based on the cable connector sizes being used.
 
iwire said:
Actually the code does go beyond that but it is done based on the raceway sizes and if there are no raceways it is based on the cable connector sizes being used.
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Actually it is based on the minimum sized raceway that would be required if the cable was just individual conductors. Take a look at the last paragraph in 314.28(A)(2).

Chris
 
A few comments:
(a) Your 6 X dimmers ion is base on angle pulls. If you happen to be going straight thru the the dimension is 8 X.
Also notice the distance between entries must be 6X for angle pulls so
box entry point in important
(b) If you happen to be going straight thru then your 12" dimension would be between entries. Your width would only be what's necessary for your splices, etc. so a 12" long 4 x 4 wireway might help if, as you say, spacing is tight.
 
raider1 said:
Actually it is based on the minimum sized raceway that would be required if the cable was just individual conductors. Take a look at the last paragraph in 314.28(A)(2).
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Thanks, I was going by memory and I thought the note talked about cable connector size.
 
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