I found an obviously overloaded electrical box under a light in my basement. It has six 14/2 wires running into
it. One wire feeds power from the panel and another goes to the light switch. The four others branch out supplying
power elsewhere.
I assumed that I could just fit a lager electrical box but I talked to an electrician who told me that I need to
have the power enter one box and then split it into two other boxes where the power branches off. I am trying to
understand that logic. Just for my own curiosity isn’t a larger box sufficient?
Replies
One big box would satisfy the code. You are looking at 13 wires (6 black, 6 white and all the grounds that count as one) times 2 cu/in per wire. A 2 1/8" deep 4x4 box would work but if you used the larger 4 11/16 box you would have plenty of room to work and you can still get a ring to bring that down to a device sized hole for the light.
Do note that it's often the case that you can't jamb the "legal" number of wires into a box and get the cover on -- it's always good to go larger if you can.
Also note that any "device" in the box (switch or outlet) must be accounted for by subtracting out the appropriate number of cubic inches.
In your case it may be that some of the wires coming in are simply too short, and additional boxes are needed to supply slack in them. Also note that there are only so many knockouts available on a box, and with six wires entering you're likely running short of knockouts that are reasonably well positioned.
A square box typically has 12 KOs around the sides (3x4) and 5 in the back so that will not be an issue. Mounting will block 3 or more of those tho. You might be able to poisition the box an inch or two to one side to make up for a cable that is too short.
This really sounds like a pretty trivial fix if the ceiling is open.
I would go with the 4/ 11/16 box and then you have plenty of room.
The light will be below the box, on the ring, so it will not count on the fill number. The ring can even add an inch or so anyway.
Since you would end up with almost twice the space you need for 6 #14/2 cables, it should not be a problem. You probably do want to "tree" the neutrals. Splice a couple pigtails on to the original one coming in from the line side and splice the rest to those pigtails so you keep it down to 3 or 4 under each nut.
I put a small grounding bus like you use in a panel in the back of these "kludge" boxes to terminate the grounding wires without that wirenut mess. Use the tapped 10-32 hole to mount it. wire in the grounds first and press down all of the wires before you start working on the current carrying condiuctors. You can usually terminate 3 grounds per hole by the listing.