Wiring for Wet Metal Walls

[Little Bill]

An electrician friend asked me to help with wiring an addition to a building. It is a slaughter house and the area will have metal walls but could be subject to wash down.
Some questions:
Would the wiring have to be wet rated if not exposed but behind a metal wall. The wall, as I understand it, is just corrugated metal panels. Not sure if there will be any sealant at the seams or not.

Builder asked that the receptacles be "adjustable". Not adjustable in the normal fashion as in adj boxes that can be run in/out, but he wants them to be able to be moved to hit a flat spot on the metal panels and not on a ribbed section.
How would you do something like this?
Only thing I could think of was to leave wiring in the wall and cut-in boxes where flat spots were. Problem with that is the boxes would have no support to speak of. A pop-in box wouldn't hold very tight on this metal. Any ideas on how to leave the boxes & wiring to mount when the panels are in? Or other ideas about this?

 

[infinity]

A old work style metal box would work if riveted to the metal through the holes on the ears of the box.

 

[Little Bill]

That might work. Do they make a 2G or larger box like that in case there is a need for them?

 

[Fred B]

That might work. Do they make a 2G or larger box like that in case there is a need for them?

That box is gangeble, just take side screw and side off 2 or more boxes and join them together.

 

[Dsg319]

An electrician friend asked me to help with wiring an addition to a building. It is a slaughter house and the area will have metal walls but could be subject to wash down.
Some questions:
Would the wiring have to be wet rated if not exposed but behind a metal wall. The wall, as I understand it, is just corrugated metal panels. Not sure if there will be any sealant at the seams or not.

Builder asked that the receptacles be "adjustable". Not adjustable in the normal fashion as in adj boxes that can be run in/out, but he wants them to be able to be moved to hit a flat spot on the metal panels and not on a ribbed section.
How would you do something like this?
Only thing I could think of was to leave wiring in the wall and cut-in boxes where flat spots were. Problem with that is the boxes would have no support to speak of. A pop-in box wouldn't hold very tight on this metal. Any ideas on how to leave the boxes & wiring to mount when the panels are in? Or other ideas about this?

I just recently helped on a rough in on a wash bay building(tin walls) wooden studs. We romexed inside the studs and our putting Red dot boxes and bubble covers.

Since fastening to the tin wouldn’t be very reliable, we had carpenters build a frame to mount the devices on between the studs and just left enough wire (slack) near the device to move left or right to land on the flat spot of the tin once they put it up.

 

[Little Bill]

That box is gangeble, just take side screw and side off 2 or more boxes and join them together.

I didn't notice the box was gangable. I've used them but not in a case like this job.

 

[Little Bill]

I just recently helped on a rough in on a wash bay building(tin walls) wooden studs. We romexed inside the studs and our putting Red dot boxes and bubble covers.

Since fastening to the tin wouldn’t be very reliable, we had carpenters build a frame to mount the devices on between the studs and just left enough wire (slack) near the device to move left or right to land on the flat spot of the tin once they put it up.

Did the carpenters cut out the panels where the boxes would be?

 

[Dsg319]

Did the carpenters cut out the panels where the boxes would be?

Yeah they were going too. Another reason they framed up for our devices between the studs was because with the red dot boxes and bubble cover they hang wayyy out. So they was able to recess the box some.

 

[infinity]

Did the carpenters cut out the panels where the boxes would be?

Maybe, we have a punch that cuts a rectangle out the perfect size for the box. It works just like a round KO punch so we can cut our own in metal.

 

[Little Bill]

Thanks guys, that gives us something to start planning with. Would NM cable be allowed behind the metal wall, it also will have metal studs? I ask because of both the water spray and the metal studs.

 

[Todd0x1]

Caddy makes a horizontal mounting bar that goes between the studs with a sliding clip the box attaches to. Box slides left and right until you latch the mounting clip. The bar is TGSB series and the clip is TSGLDR1. They're only a couple bucks a piece.

Heres the instruction sheet

https://www.erico.com/catalog/literature/CFS421_C.pdf

 

[ElectricMatt]

Thanks guys, that gives us something to start planning with. Would NM cable be allowed behind the metal wall, it also will have metal studs? I ask because of both the water spray and the metal studs.

Just some advice from someone who works daily in a wash down environment. Do not use NM cable. Run conduit to an accessible location because you will have plugs, and wiring degrading at a much faster rate than normal conditions. I would not recess the plugs, I would do cord drops with a wet rated receptacle. (Hubbell has a pretty good selection with good quality)

If the owner insists on recess as where his builder is going to start installing the metal panel from. Then you can measure to fall in the flats and not the rib. If it is typical R-Panel you are looking at 12” on center of each rib.

Personal experience here, you cannot control water, you can do your best to manage it. Ultimately it will get into everything over time and is very destructive.


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