1

I used a box to splice wires when moving conduit during basement renovations. I'm in Chicagoland area and use 1/2" EMT. I spliced 4 circuits back together in a 4 x 4 x 2-1/8 box with cover. The circuits are 2 15A and 2 20A circuits, which are 4 12 gauge and 4 14 gauge wires.

My box fill calculations are: No continuous wires, so there are 8 12 gauge and 8 14 gauge wires entering box. 8 x 2.25 + 8 x 2 = 34 cu. in. The box capacity is 30.3 cu. in. with flat cover plate

Is this correct? If so, can this be remedied with a 7.3 cu in mud ring and blank plastic cover plate?

2 Answers 2

2

The mud ring sounds like it would work as long as the cu inch is listed, but now you're stuck using a plastic cover. You could use a box extender with a regular 4x4 cover -

box extender

The one above is a Garvin BEX-450, a 1/2" extender for a 4" box, but there are many many variants available.

0
1

Yes, you can use a mud ring and blank steel cover. They make those, even if your local purveyor does not have them.

If a receptacle might be useful there, you can use a 1-gang domed mud ring intended for a receptacle, and fit one. You'll pay the cubic-inch cost of a yoke: 2 wires (4.5 ci).

They also make extension boxes in a variety of styles, my stock in trade is one that simply gives you another 1.5" of 4x4 box. I use them all the time, as they have the same cubic inches as a straight 4x4x1.5" box - easy to remember.

Although when I expect to do that many splices, I aim for 4-11/16 (aka 120mm) square boxes, typically 2-1/8" deep by default for 42 ci, though they also make deeper ones. These are much cheaper at real electrical supply houses than the big-box stores (which is ironic, since it is a big box).

1
  • Thanks, this solution would be cheaper and quicker, however, the 1/2" solution works better for me in this case as it's lower profile.
    – Mark_B
    Oct 30, 2018 at 19:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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