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Discussion Starter · #1 ·
Hey guys I have a couple runs of 1 1/4" emt and I am trying to properly size the junction boxes to each room. I was looking at rule 12-3034 (5) and using table 22. I know I could just look at the run and take a guess at the box size I just want to do it properly and was wondering if I use table 22 for a larger junction box. Like a 6x6 or 8x8? Thanks for the help
 

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In cases of junction boxes used for making connections from pulled wire runs to bx cables in rooms, I always like to go at least 10 x 10, unless there are very few bx cables.

If you go by the code, you can stuff a 6x6 by 4 inch deep box with an unwieldy amount of wires and connections. Here's my calculations:

6 in x 6 in x 4 in gives us a volume of 144 cubic inches.

Converting to mL (144 divided by 0.061) gives us 2,360 mL.

Now, if you have all 12 gauge, you can calculate the box fill for connecting one two wire bx to conductors from a conduit. That would be the same space as 5 conductors, given the two marrettes.

That number is 143.5 mL. So, dividing that into 2,360 mL gives us the space, by code, to bring sixteen 12/2 bx cables into the box, if the box is the end of the run and does not have any conductors running through it.

In my experience, it is too much of a pain to keep all of those joints neat and tidy in that small of a box. That's why I always go 10 x 10 or 12 x 12 if I can. Just for grins, a 12 x 12 can have up to 65 12/2 bx cables terminated in it. Just too much if you ask me.

TL:dr At least 10x10 makes it much easier to keep things neat, despite most likely being overkill as far as code goes.
 

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This is why I hate 6x6 boxes, it's the smallest almost box shape you can get. Unless you're putting extension rings on 4 11/16 boxes but I won't go there. The worst is a contactor in a 6x6 with extra connections inside. Hack!

I agree with 10x10 minimum. If you're gonna cut corners on a job fine but at least put a 10x10 for the main box, it's only a couple of bucks more then an 8x8!
 

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Discussion Starter · #8 ·
In cases of junction boxes used for making connections from pulled wire runs to bx cables in rooms, I always like to go at least 10 x 10, unless there are very few bx cables.

If you go by the code, you can stuff a 6x6 by 4 inch deep box with an unwieldy amount of wires and connections. Here's my calculations:

6 in x 6 in x 4 in gives us a volume of 144 cubic inches.

Converting to mL (144 divided by 0.061) gives us 2,360 mL.

Now, if you have all 12 gauge, you can calculate the box fill for connecting one two wire bx to conductors from a conduit. That would be the same space as 5 conductors, given the two marrettes.

That number is 143.5 mL. So, dividing that into 2,360 mL gives us the space, by code, to bring sixteen 12/2 bx cables into the box, if the box is the end of the run and does not have any conductors running through it.

In my experience, it is too much of a pain to keep all of those joints neat and tidy in that small of a box. That's why I always go 10 x 10 or 12 x 12 if I can. Just for grins, a 12 x 12 can have up to 65 12/2 bx cables terminated in it. Just too much if you ask me.

TL:dr At least 10x10 makes it much easier to keep things neat, despite most likely being overkill as far as code goes.
Ya I figured it out like that. Ya you can put alot of #12s in a 6x6
 
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