In our house, whenever there are receptacles on two sides of the same wall, they are not in the same place. They are never placed back-to-back, even if they are on the same circuit.
Is there a safety reason for this? Why don’t they put them in the same place and use one electrical box that goes completely through the wall?
Janet
Replies
It's in the process.
They used to make through the wall metal boxes. I haven't seen one in a long time. I think the main reason this is not done is that most electrical bids and materials take-offs are done from plans. It's easy just to count the number of single, double, tripple, etc. boxes and bid the job. Then you buy the materials the same way. There's no particular cost saving in using through the wall boxes; it just complicates things for the electrician prior to being on the job site. Quite often low voltage stuff (TV, phone, etc.) uses back to back plaster rings.
There may be a fire code issue. Depending on what the wall is separating, you may have restrictions on penetrations and a box going from one side to the other or even 2 boxes too close together on both sides of a wall. would be a penetration.
Another issue can be box fill. A 3x2x3.5 cu/in box (open, with ears at both ends) would take 2 devices and 5 wires if they were #14 but not #12 and even then it is a tight fit.
I don'y know of anyone who actually makes that box.
Box fill is the reason I'm asking. We've got a dining room switch nearly in the same place as the kitchen switch on the other side of the wall. Their placements overlap.
I'd like to have a dimmer in the dining room, but can't find a dimmer that is shallow enough to fit in the box, which is crammed full of wires. There are four cables entering the box, all spliced together, plus the switch.
In contrast, the electrical box on the kitchen side is nearly empty. It was installed during an add-on, and I can't imagine why they didn't redistribute the wires at that time, or use one of those through-the-wall electrical boxes, or site the kitchen box so the dining room box could be replaced with a deeper one.
Will an electrician be able to combine the boxes?—or will installing a dimmer require plaster work and remodeling?
Janet
No electrician is going to "redistribute" in-place wiring unless he has to touch the wiring for some other reason. There's no profit in it, and there's a non-trivial chance of screwing something up.
Good point. I've been wondering about the economics of homebuilding—but that's for a later post.
Janet
If you can tolerate a drywall punch and paint, they can swap out that box for a bigger one fairly easily. You might only end up with a little bigger cover or a 2 gang (old work) box in that spot.
A 2-gang box would work. I'd probably go that way, except the switch is behind a door that is usually left open. I've decided to move the switch and put in a larger box. More damage to the original plaster, but more convenient access. I just hope the repair doesn't stand out.
Janet
RECEPTACALE LOCATION
Another reason you don't see back to back is that code requires that outlets be located at specific distances and locations. A location in one room may not be the same location in an adjoining room.
Never mind; moot point
I've decided to relocate the box that has too many wires, because the switch is in an inconvenient location. That will take care of two problems, because the electrician can install a larger box while the wall is open.
Janet
Generally, they don't put them back-to-back because they'd bump into each other. And a through-the-wall box would need to be precise in its depth to be flush on both sides.