More help. Ways to mount exterior receptacle

[rev1]

Thanks to all here, I've got my load center (breaker box) mounted and a few runs of conduit for some inside receptacles and the overhead door openers. Now I need to install an outdoor receptacle. I've read some threads here and have decided to surface mount a weatherproof box and in-use cover. What I need help on is how to securely mount the weatherproof box to the steel siding. This is a all metal building, no studs. Do I drill a 3/4 or 1" hole in siding and use a plywood backing on the inside (also with a 3/4 or 1" hole for the conduit to pass thru)? If so, do I need to attach the plywood to the inside or will the weatherproof box screwed to the siding and the plywood be sufficient?
Is there a better way?

 

[Alchymist]

2X6 inside, drill hole through for pipe ******. Matching hole through siding. Assemble with a box inside and outside back to back. Pipe ****** long enough to just enter both boxes, secure with standard electrical nut (the thin serrated one). Couple screws in the outside box through the siding into the 2X. Inside run wire by whatever method you're using to the inside box, jumpers to the outside outlet. I usually put a GFCI in the inside box and feed the outside outlet from it. I also run a bead of silicone caulk around the top and sides of the outside box to keep water from getting between box and siding.

 

[Charles (in GA)]

I used 3/4 plywood in three places on the inside of my steel building. I have the typical fiberglass/vinyl backed insulation on the inside that is captured between the sheets and the girts/purlins. I took the plywood and rounded the corners with a very wide radius, and then used a router to round the edges, again with a wide radius, so it would not dig into the insulation and cut it. One place I used it was mounting the meter socket on the outside of the building, the other was mounting the chimney support for the used oil heater.

Charles

In the lower right image below, you can see the white painted plywood behind the panel and switch boxes.

 

[rev1]

Charles, I also have the insulation. Does trapping the insulation between the plywood and the sheet metal cause whatever is being mounted (in my case the outdoor receptacle) to be unstable? Or does it tighten down enough to compress the insulation to keep it from being soft?

 

[Mustang51js]

Just use zip scews or 6/32 screws with nuts on the back,silicone around the box which should be done no matter what way you mount it. You can pipe it or use bx cable to it.

 

[sberry]

I drill a 7/8 hole, stick an emt connector thru from the inside, put a gob of silicone on the back of box, have a helper or if by myself line it over the hole and zip a couple sheet screws thru the box in to the siding to keep it from rotating till the goo sets, spin, thread connector in to the box, pinches the sheet to it. I see Mustang beat me to it, same version.