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Shallow electrical boxes?


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#1 miamicanes

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Posted 06 September 2008 - 09:44 AM

Does anybody know where I can get shallow (1.25" or less from front surface to rear surface) electrical boxes... ideally, ones that at least respect the spirit and intent of NEC, if not its absolute letter?

Here's my problem: the wall is a party wall. As far as I can tell, it looks like the builder did something like this:

* build a wall from concrete blocks, put rebar in the holes, and fill them with grout (runny concrete)

* glue or screw the outlet and switch boxes to the exterior of that wall

* apply another inch or so of thick, plaster-like concrete (or shotcrete) to each side of the wall, leaving the boxes half-embedded in the newly-applied concrete layer

How did I come to that conclusion? Well, for one thing, I looked. I scraped away some of the insulation, and noticed that the concrete wall behind it is smooth, not rough like normal concrete blocks. It also appears to be continuous, and envelopes the existing outlet boxes. I know that under at least the current building code, penetrating the party wall itself for things like pipes and wires is taboo, and I'm pretty sure that even back in 1982, the building code required that the houses on either side of it be at least nominally independent of it. Among other things, that would explain why the ribs in the concrete suspended slabs that form the second floor and roof seem to run from front to back rather than from side to side.

Anyway, the problem is that the current outlets are partly embedded in concrete, and I don't have the means of replicating that. If I scrape away the foam, I have about 1.25 inches for the entire outlet box, from rear to front exterior surface. I've found shallow plastic boxes at Home Depot, but there are at least two problems:

* They're only single-gang. I need at least double-gang, and I'd prefer to get triple-gang with double-gang front plate to give me more room alongside the outlets and compensate for the lack of depth.

* They're plastic. As I understand it, you aren't allowed to terminate a metal conduit pipe at a plastic box... only romex or aluminum flex. Presumably, the rationale is that if you see a solid metal conduit leading away, you should be able to assume there's another metal box at the other end, and if I wanted to put one or more plastic boxes between two existing metal ones, I'd officially have to eliminate ALL of the metal conduit between those two boxes and replace it with romex or aluminum flex. I'll probably end up having to do this anyway, but if I can stick with metal boxes, I'd just as soon keep it that way.

So... is there an online source for shallow metal boxes? Or at least plastic ones? Is this something that any decent electrical supply store should carry, even if Home Depot & Lowe's doesn't?

#2 upstatemike

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Posted 06 September 2008 - 10:14 AM

Does anybody know where I can get shallow (1.25" or less from front surface to rear surface) electrical boxes... ideally, ones that at least respect the spirit and intent of NEC, if not its absolute letter?

Here's my problem: the wall is a party wall. As far as I can tell, it looks like the builder did something like this:

* build a wall from concrete blocks, put rebar in the holes, and fill them with grout (runny concrete)

* glue or screw the outlet and switch boxes to the exterior of that wall

* apply another inch or so of thick, plaster-like concrete (or shotcrete) to each side of the wall, leaving the boxes half-embedded in the newly-applied concrete layer

How did I come to that conclusion? Well, for one thing, I looked. I scraped away some of the insulation, and noticed that the concrete wall behind it is smooth, not rough like normal concrete blocks. It also appears to be continuous, and envelopes the existing outlet boxes. I know that under at least the current building code, penetrating the party wall itself for things like pipes and wires is taboo, and I'm pretty sure that even back in 1982, the building code required that the houses on either side of it be at least nominally independent of it. Among other things, that would explain why the ribs in the concrete suspended slabs that form the second floor and roof seem to run from front to back rather than from side to side.

Anyway, the problem is that the current outlets are partly embedded in concrete, and I don't have the means of replicating that. If I scrape away the foam, I have about 1.25 inches for the entire outlet box, from rear to front exterior surface. I've found shallow plastic boxes at Home Depot, but there are at least two problems:

* They're only single-gang. I need at least double-gang, and I'd prefer to get triple-gang with double-gang front plate to give me more room alongside the outlets and compensate for the lack of depth.

* They're plastic. As I understand it, you aren't allowed to terminate a metal conduit pipe at a plastic box... only romex or aluminum flex. Presumably, the rationale is that if you see a solid metal conduit leading away, you should be able to assume there's another metal box at the other end, and if I wanted to put one or more plastic boxes between two existing metal ones, I'd officially have to eliminate ALL of the metal conduit between those two boxes and replace it with romex or aluminum flex. I'll probably end up having to do this anyway, but if I can stick with metal boxes, I'd just as soon keep it that way.

So... is there an online source for shallow metal boxes? Or at least plastic ones? Is this something that any decent electrical supply store should carry, even if Home Depot & Lowe's doesn't?


You might be able to find a metal wiremold box that shallow. They make adapters to legally connect them to thinwall conduit. I'm not sure if it would be appropriate for your application though.

#3 Steve

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Posted 06 September 2008 - 10:27 AM

Raco makes the 185 which is 1.25" and is metal, Carlon makes the regular blue plastic B108R-UPC or other also 1.25.

You should be able to get them at an electrical supply house or online for sure.

Edit: Sorry, the Carlon is just single gang. The Raco is dual gang.

Edited by Steve, 06 September 2008 - 10:32 AM.


#4 miamicanes

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Posted 06 September 2008 - 11:18 AM

AWESOME! The '185 is exactly what I was looking for! Thanks! :blink:

#5 Photon

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Posted 06 September 2008 - 11:26 AM

An electrical supply house that supports the pros will likely have what you need as well as the answers to some of the code questions like is conduit even required under currend code.

Around here there is a limit to how many outlets you can wire to a single circuit. You might ask them about that if you shop where the pros shop.

#6 miamicanes

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Posted 06 September 2008 - 01:52 PM

Around here there is a limit to how many outlets you can wire to a single circuit. You might ask them about that if you shop where the pros shop.

Ah, yes. The wonderful governmental logic that says you can't put in more outlets, but it's OK to plug power strips into power strips plugged into multi-outlet adapters instead. :blink:




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