j-box mounting ideas

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SceneryDriver

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Electrical and Automation Designer
We're turning a 20' sea container into a mobile shop for a large upcoming install job overseas (on a ship, actually). I've been tasked with fitting it out electrically.

Unless anyone has better suggestions, I'm planning on welding short sections of half-height Unistrut at the locations where I need to land my breaker panel, disconnect switch, light fixtures, and j-boxes. My goal is to not penetrate the shell of the container, lest I have water infiltration issues.

We will own the container, and there will be other welding going on in the container to get it ready anyway, but I thought I'd solicit other suggestions for device and enclosure mounting. I'd love to skin the inside of the container with plywood, but I'm told that's not an option due to cost issues.


Thanks,

SceneryDriver
 
Without an interior skin, welding would work the best.

Or, possibly spanning interior supports with strut, screwed to the interior supports, but that seems like a possible problem with vibration etc.
 
I've done them 3 different ways:

1. Screw everything down with a dab of weatherproof caulk in each hole.

2. Welded strut like you mentioned, but then you'll have rust issues if you don't properly prep and paint the burned off areas.

3. 3M VHB tape to secure the boxes and conduit to the wall. I also epoxied around the boxes, just to make sure they were good and anchored. This particular container was getting spray foamed on the inside so no one would ever see the VHB tape or epoxy. That was 1.5 years ago and it's still holding just fine.

Since your customer isn't willing to spend a few bucks to line a small 20' container with plywood and the fact it's going on a ship with potential rust issues, I'd recommend option 1. I'd look for a premium weatherproof caulk to seal the screw holes.
 
Lack of skinning it with plywood, it will be much easier and convenient just to mount the electrical equipment to the surface and as mentioned earlier, use good quality caulk.

Ustrut will work if you know exactly where your electrical is going.

(Added) Also how are you going to support and secure conduit?
 
edward said:
Lack of skinning it with plywood, it will be much easier and convenient just to mount the electrical equipment to the surface and as mentioned earlier, use good quality caulk.

Ustrut will work if you know exactly where your electrical is going.

(Added) Also how are you going to support and secure conduit?
Click to expand...

If the walls are single-corrugated, I'll probably have to weld short sections of strut and use strut hangers for the conduit. Kinda dumb, I know.

I do know exactly where the electrical is going, as I'm going to be the poor sparky installing it :)

I'm told there's a good chance the container the customer is sending to us will have double-corrugated walls, so there will actually be hollows in the walls that I can put a Tek-screw into without breaching the waterproof integrity of the container. If that's the case, I'll just use self-tappers for everything.

All in all, it seems like a lot of crap to go through to save the cost of ~12 sheets of plywood. Rust won't be an issue if we weld; we'll treat any burned spots on the outer skin with the proper paint, so that's no big deal.



SceneryDriver
 
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SceneryDriver said:
We're turning a 20' sea container into a mobile shop for a large upcoming install job overseas (on a ship, actually). I've been tasked with fitting it out electrically.

Unless anyone has better suggestions, I'm planning on welding short sections of half-height Unistrut at the locations where I need to land my breaker panel, disconnect switch, light fixtures, and j-boxes. My goal is to not penetrate the shell of the container, lest I have water infiltration issues.

We will own the container, and there will be other welding going on in the container to get it ready anyway, but I thought I'd solicit other suggestions for device and enclosure mounting. I'd love to skin the inside of the container with plywood, but I'm told that's not an option due to cost issues.


Thanks,

SceneryDriver
Click to expand...


You can try attaching to the container surface with weld stud fasteners.
https://www.mcmaster.com/#93865a215/=15ztm1r
 
Can't have 12 sheets of plywood because of cost - but the unistrut may actually cost more.

Or is the strut already in the inventory and something that can be taken for this purpose without being noticed by the bean counters?
 
Buy or rent a stud welder. We use a stud welder to install stuff on large steel beams and columns. For boxes and conduit you can use 1/4" studs. Once it's set up the process is very fast.

arc-process-Converted.jpg
 
infinity said:
Buy or rent a stud welder. We use a stud welder to install stuff on large steel beams and columns. For boxes and conduit you can use 1/4" studs. Once it's set up the process is very fast.

arc-process-Converted.jpg
Click to expand...
That should cost less then 12 sheets of plywood:)
 
Plywood sounds like the most versatile idea but how do you fasten it to the metal, construction adhesive?
 
I thought you might want to see how the shop container turned out. A few pictures:

332.jpg Breaker panel and test points panel.

333.jpg Inside the test points panel. Test points are fused at 1/4A with Class-CC fuses.

337.jpg Incoming power service disconnect. 600V fuses to account for any possible incoming supply voltage to the transformer.

350.jpg 60A 3-phase pin-and-sleeve connectors between main disconnect and breaker panel. This will allow the transformer (if needed) to be swapped, depending on site supply voltage. We lit up the shop with building-supplied 208V 3-ph, so we didn't have the trafo installed. There's a 15kva 3-ph 400V delta ---> 120/208V wye 50Hz transformer showing up tomorrow, for the install on the ship.

338.jpg Incoming power lugs enclosure. Cable gland goes out through the side of the container. Extremely temp power tails temped in.

341.jpg Sections of Unistrut were welded to the container and I attached all the boxes to them.
 
Cow said:
Looks good. I've never seen anyone install "test points" before, cool!
Click to expand...

Pretty standard on lots of portable entertainment industry equipment that has to be connected to "unknown" power. Used to be that you'd just open the disconnect door or pull the panel cover and meter the incoming power, but live work rules make that a no-no these days. Those 1/4A Class-CC fuses are quite fast acting and would (probably) protect your meter if you accidentally had it set to current instead of voltage. At least it won't blow up in your face. :)


SceneryDriver
 
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