0

Can I put seven 12/2 cables in one 4 x 4 x 2-1/8 square metal junction box? According to some box fill calculators, this may be a tad too many wires for this junction box. However, I'm hoping I'm wrong. Other wise I may have to use two junction boxes.

Adding context: This junction box will serve 4 new closet lights and new light switches, along with an existing bathroom vanity light and switch and 4 existing recessed led lights (on one switch). Along with the power source line in, it is a total of seven 12/2 cables.

1
  • 1
    perhaps daisy chain some of the closet lights
    – Jasen
    Dec 28, 2022 at 11:55

1 Answer 1

4

12 AWG = 2.25" x 15 (14 conductors plus 1 for all the grounds) = 33.75"

In NEC 2020 (not adopted everywhere yet), every 4 grounds count as 1:

12 AWG = 2.25" x 16 (14 conductors plus 2 for all the grounds) = 36.00"

4" square 2.125" deep box I found listed as 30.3", which is less than 33.75". So it won't work.

Add a domed cover for another 7", total 37.3", and you are OK even with NEC 2020.

You can also use a 4.6875" (4-11/16") x 2.125" box sized at 42". That gives you room to spare - enough for one more cable.

I found a great PDF of box dimensions - not everything listed on Home Depot or other retail sites includes cubic inches.

1
  • 3
    The NEC 2020 rule is that grounds are 4 for the price of 1. So that would be 2 grounds. A domed cover may add enough cubic inches to make a difference. Dec 28, 2022 at 7:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.