Wiring in trench

[clausb]

We are providing consulting/engineering services for an industrial client for a new facility. They want to run the power from the electrical room out to the production lines and throughout the production lines in a "trench" system. We have figured out that what they are talking about is a fairly large trench formed into the concrete floor with cable tray(s) in it and a metal cover. We have never come across this before, but the client insists they have seen it and it is what they want. We can come up with MANY reasons not to do this but they cannot be convinced that this is not a normal way to power production equipment. For the most part the production process is dry so water/moisture in the trench will not be a normal thing. Our concerns are how dirty the inside of the trench will get, fork truck traffic over the trench, how to get the wiring out of the trench to control panels and production equipment, how to make the bends in the cable tray (the sweep of a 90 degree bend will make the trench huge).

We have done code review and cannot find any reason to say that it violates code.

Does anyone out there have any experience in this type of application? Have ideas or recommendations for us? We have extensive experience in industrial facilities, but have never come across installations like this.

 

[charlie]

The closest I have seen is the wiring in our substation yards. We have a buried concrete trough that is flush with the crushed stone and have lift off pieces of concrete that covers the trough. All of the medium voltage is in duct lines and the high voltage is overhead. I am sure that this doesn't help with your question but it sounds similar. :smile:

 

[don_resqcapt19]

I have seen this in a number of industrial applications. In some of them they just racked the cables in the trench without the tray.

 

[augie47]

Inspected such installations using Art 390 as a guide.

 

[Cow]

Our company did a concrete in-floor gutter once in an electrical room. It's right up against the wall so the MCC straddles it and you chase the wires under it. Probably 12" wide and 18" deep. This gutter wrapped two of the walls around the room, where the MCC stopped, aluminum diamondplate covers the rest of the gutter. If disconnects etc. were set a ways above the diamondplate, pipe runs down the wall and through a slot cut for it so you're still able to slide the treadplate off the gutter. You can use bridle rings or j-hooks hung off the side of the gutter wall to hold your wires too.