box fill for metal 42 cu in box

Hi all,

I'm adding 4 new circuits to my main panel for a kitchen remodel. To get the new wires from the panel into my house, I added a new conduit from the panel which enters into my crawl space. The new conduit goes to a junction box. I will have 4 hots, 4 neutrals and 4 grounds coming into this box, via the conduit (1 inch EMT). Going out of the junction box I will have 4 romex cables (going to the 4 new circuits).

I have a 42 cubic inch metal box. There is nothing in the box other than spliced wire and wire nuts. I think this should be OK. Here is my calculation:

I have 8 hots, 8 neutrals and 8 grounds in the box. The grounds as a whole count as one conductor. The 8 hots and 8 neutrals add to 16 conductors. That's a total of 17 conductors. To my knowledge each 12 awg wire counts as 2.25 cu inch. So I have 17 x 2.25 = 38.25. So I think I should be fine. Can someone confirm this.

This one interests me as well

Antonio4791 said:

I have 8 hots, 8 neutrals and 8 grounds in the box. The grounds as a whole count as one conductor. The 8 hots and 8 neutrals add to 16 conductors. That's a total of 17 conductors. To my knowledge each 12 awg wire counts as 2.25 cu inch. So I have 17 x 2.25 = 38.25. So I think I should be fine. Can someone confirm this.

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Your math is correct.

My chart calls a # 12 = 2.62 cu.in. which would make you a bit undersized, but in the real world it probably does not make a big difference.

You could have used one ground wire from the panel, but the math is correct, just like Mike said.

thanks

Thanks guys. I'll continue with my plan.

Now I will have everything on dedicated circuits.

hj said:

My chart calls a # 12 = 2.62 cu.in. which would make you a bit undersized, but in the real world it probably does not make a big difference.

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The NEC allowance for #14 is 2 CI, for #12 2.25 CI.