ECN Forum Forums General Topics of the Trade General Discussion Area cold room wiring method

I need to install conduit and receptacles in a large cold room that the fire marshall has classified as Class1 division 2 location. (they store flammable chemicals in this room) The walls of the cold room are lined with 3" foam, my two questions are:

1. how do mount conduit and or boxes to a foamed wall. Do i need to penetrate through the foam and mount to concrete or there are special hardware for foam?

2. I am not very familiar with article 500, is EMT allowed with this location?

Thank you.

Class1 Div 2 requires threaded IMC or RMC, no EMT.

You could put lag shields into the concrete and use conduit hangers on 4 1/2" or 5" hanger bolts ("wood screw thread on one end, machine thread on the other)with a jam nut on the machine thread at the surface of the foam and another nut securing the hanger.

It is an illusion that the walls are pure foam.

In every box I've ever worked the panels arrive as wood framed elements: polyurethane foam as a core with edges of wood and a surface layer of metal -- thin stainless steel approved for food service.

So you use the wood as support -- the foam won't hold any weight to speak of.

If the raceway is overhead you may have to bolt j-hooks clean through to the topside. It all depends on how much weight you have to hang.

It also sounds like you'll be mounting explosion proof jelly jars -- the ones used at refineries. Talk about $$$$.

Tesla,
The walls have foam without any rigid piece. It is foam and covered with foil.
i probably have to anchor to concrete as greg mentioned.

Yes i need explosion proof boxes and rated receptacle. One receptacle with the box is about $400. Yikes.

A seamless cold box...

Amazing.

I'm puzzled....

How did they pull that off?

it is not seamless, it just doesn't have any rigid piece to it. It is not like the regular walk in freezers and similar have sheet metal walls with foam inside but this one is only foam with foil covering.

I saw a flower cooler like that when my wife was in the flower biz. The sheet metal box is mostly for the health inspector from what I see. They need to be able to wash it down.
I did not pay attention to how they hung the lights and they were not dealing with Art 500. This was Miami before Andrew. It may have been festoon lamp bases on an orange cord in those days. ;(

Tesla, those cooler panels are manufactured in a variety of ways. Some brands do not have any formwork in them, relying instead on the folds in the sheet metal at the seams to hold it all together.

I've seen both aluminum and stainless 'skins.' The question we're asked is: How do you mount stuff to it?

I don't like punching all the way through, as that often introduces other issues (like water leaking). For heavy loads, that might be your only option.

Sheet metal screws might work fine for conduit straps, but boxes and fixtures will need more. You might have to hollow out the area behind your holes in order to use toggle bolts.

Anybody think of checking with the mfg??

I can't check with the manufacturer because the room is built on site. Imagine a warehouse with concrete walls and it has foam board glued to the concrete walls. It is more less a room with an oversized AC that keeps the room cold and this cold room is built inside a 30 sqft warehouse that stores corrosive material.

I think i will do all of the conduit work on the outside of this cold room then penetrate into the cold room. That will eliminate the RMC conduit + the associated labor, and .....

Now, the question can i seal my penetrations with Fire putty or caulk?