Electrical – Splicing wires in a big box

electricalwiring

I need to splice several Romex wires in my house. Can I use an electrical box the size of a breaker box (empty)to bring several circuits in for splicing? The box would be within a few feet of the breaker box and is needed because some of the old circuits as well as some new ones have to be joined. This is on a remodel and about 1/3 of the wires are not being replaced, but need to be spliced with new wires. The old Romex cables are of current code, just a bit too short to make it to the breaker box that is about 4' away

Best Answer

Yes, that's fine. I do it myself. I bought some 10x10x6 boxes for splicing some wires that had been cut short by copper thieves, and also to house relays for some lights.

You can also connect the box(es) to the service panel by lengths of EMT conduit (which is exactly what I do). This takes care of grounding. You are only allowed 4 circuits per conduit (unless the conduit is <24" long), so in the case of my big 6x10x10 box, I ran 4-6 conduits between box and panel.

For simpler jobs, my preference is to run a 1/2" or 3/4" conduit to either a 4" or 4-11/16" square junction box (much cheaper at the electrical supply than the big-box store). Then I bring 4 circuits into each box. For the last hop from box to panel I use stranded THWN-2 individual wires, which is easier to work with and is legal in conduit. (the reason not to use stranded THWN everywhere is it's hard to attach to receptacle/switch screws, until you get the knack).

These boxes are also nice places to mount GFCI deadface or receptacles if you want to protect a whole circuit, but don't want to spend $40 for a GFCI breaker.

You need 4-1/2 cubic inches per pair of non-ground wires spliced. So one 120V circuit needs 9 cubic inches, and a 120/240 split phase circuit needs 13.5 c.i. You also need one 2.25 cubic inch allowance which covers all ground wires. I use 4-11/16" boxes (or 4" square boxes with extension boxes) for the necessary cubic inches; (42 c.i. and 22+22 c.i. respectively).