# box fill for metal 42 cu in box

Discussion in 'Electrical Forum discussion & Blog' started by Antonio4791, Jul 6, 2011.

1. ### Antonio4791New Member

Joined:
Jul 26, 2010
Location:
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.

2. ### BobL43DIY Senior Member

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Mar 25, 2011
Occupation:
Retired Industrial Automation controls/tech s
Location:
Long Island, NY
This one interests me as well

4. ### jwelectricElectrical Contractor/Instructor

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Jun 14, 2007
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Instructor
Location:
North Carolina

5. ### hjModerator & Master PlumberStaff Member

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Aug 31, 2004
Occupation:
Plumber
Location:
Cave Creek, Arizona
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.

6. ### jbfan74Electrical Contractor

Joined:
Jun 14, 2007
Occupation:
Electrical Contractor
Location:
Newnan, GA
You could have used one ground wire from the panel, but the math is correct, just like Mike said.

7. ### Antonio4791New Member

Joined:
Jul 26, 2010
Location:
thanks

Thanks guys. I'll continue with my plan.

Now I will have everything on dedicated circuits.

8. ### Jim PortElectrical Contractor

Joined:
Aug 22, 2009
Occupation:
Electrical Contractor
Location:
Maryland
The NEC allowance for #14 is 2 CI, for #12 2.25 CI.