pull box sizing with mix of larger than 4 awg and smaller than 4 awg

[Mountainbikeak]

I understand strait and angle pull box sizing when using just 4 awg or larger. I have a situation where I'm setting a j-box to reset bends and have 12 1" emt, one 1 1/4" emt and one 2" emt as a spare. I'll have 10 AWG thhn in all the 1" ( couple may be spares) 2 awg in the 1 1/4" and the 2" will be a spare but would count that as larger than 4 AWG when pulled in. Will I just size the junction box based on the size of the 2" and 1 1/4" and add width to accommodate the extra 1" EMT?

Thanks

 

[jumper]

You would use the full dimensions needed for all the conduits. 314.28.

I am thinking some thing like this:

x x x x. X
x x x x
x x x x. X

 

[infinity]

The NEC does not do a good job at addressing these types of installations. One could certainly use 314.28 to address the raceways with #4 and larger conductors and still end up with a box that's too small for all of the #10 AWG conductors mentioned in the OP.

 

[Dennis Alwon]

I would calculate the fill based on the conduit sizes included the conduits with the smaller wires. It would be very unusual for that to not be large enough since the conduit sizes is based on the largest conductors that could fit in the conduit

 

[kwired]

Just having a 2 inch raceway (with #4 or larger conductors in it) means at least one dimension of that box is no less then 12 inches. Additional raceways (especially containing #4 or larger) only increases that minimum dimension. Say you had a 90 degree pull on the 2 inch - that pull box is no smaller then 12x12x4.

Ignoring the conductors 4 and larger for a moment and just factoring in having all 10 AWG conductors:

-576 cubic inches = 230 #10 AWG conductors is allowed in that box, will be a rats nest if you don't use some cable ties or other method to organize them. That is 115 conductors allowed in then out if you spliced every one of them.

-Though it is not overfilled it is probably still pretty crowded in that 12 x 12 box and you might want something larger anyway.



I more then once with large conductors went with minimal requirements on sizing a box, only to end up wishing I went larger - especially if splices/taps were made in that box.

 

[jumper]

I have reread OP twice.

Where does he say how many #10s?

I just see where #10s are going into the 1”, not how many.

 

[kwired]

I have reread OP twice.

Where does he say how many #10s?

I just see where #10s are going into the 1”, not how many.

He didn't say, I was just saying minimum dimension needed for 2 inch with large conductors is 12". Had to use some assumption to get 12x12 (if a straight pull on the 2" the minimum dimension is 8 inches) and 4 inch deep was factoring in the fact that 2 inch KO plus room for locknut on termination leaves you needing 4 inch deep on most commonly available enclosures. That left us with volume in that box for 230 #10's (disregarding anything else). My point was even though 230 #10's in a 12 x 12 x 4 is in compliance with NEC - it might be kind of crowded unless they are simply straight through pulls, and to take that into consideration. Otherwise his enclosure is likely not going to be filled to the max allowed with smaller conductors simply because of the size needed as a result of having large conductors and larger raceways involved.

He said he has 12 1 inch a, 1.25 inch and a 2 inch, presumably double that when considering what leaves the box. I don't think you could get all those in as small of a box I mentioned, at least not in one side and out another as he kind of described it as a "reset for number of bends" so probably all in one side all out another side - giving you even more volume in the box used.

 

[infinity]

I see the problem of the minimum conductor per cubic inch method for smaller than #4 does not take into account the conductors that are #4 and larger. The NEC provides no guidance on how to address those larger conductor in the same box as the smaller conductors.