MC required in a commercial wall?

[AntonLargiader]

Our new commercial space is divided by walls consisting of 12' metal studs with two layers of 5/8" sheetrock on each side. The electricians are installing outlets for the other spaces before the second side of rock is installed, and they are running MC to them. The project manager asked about that and was told that it was due to being commercial (I didn't hear the complete answer).

What would require this wall to have MC cable to the outlets behind all of that sheetrock? It is built as a fire-resistant wall although is not required to be for the current use.

It's mostly curiosity on my part; I am not having those outlets installed in my portion of the space as I prefer conduit. Still, we were all under the impression that the flush outlets would just get NM-B. Everything that we demo'd in that space was NM-B but it was built many code revisions ago.

 

[AntonLargiader]

Actually part of the reason might be that the cable exits the wall section at the ceiling joists. It's 12' off the ground so I would think that would be considered inaccessible other than the run down to the panel, but I'm not an authority on that. And there is the through-the-sheetrock interface to consider. I don't know how they are handling that. In other places the Romex just came through the sheetrock at the top, but again, that was done a long time ago.

 

[theoldwizard1]

If you use NM-b with metal studs, grommets are required at every hole.

 

[Cmreschke]

Romex is suitable for commercial, however with having to purchase bushings for the metal studs and the type of strapping required for use on metal studs, it might just be about the same cost (or close to it). If it's only a small cost difference, might just be their discretion if that's what they had on hand as apposed to going and purchasing extra material. Plus the extra time involved for the romex.

If they charged you for romex and use mc cable then your making out possibly.

 

[zmaxmotorsports]

We don't use Romex on commercial work around here anyway.

 

[LXCam]

It's not required but is permissible as would be pipe and wire. And I haven't seen type NM allowed in anything other than a resi structure in over 30 years. But to be honest I can't really tell you if that's a code aspect or general conditions / specifications requirement without checking a code book.

 

[Norcal]

If there is a suspended ceiling, NM cable is not allowed above them.

 

[tab2]

If there is a suspended ceiling, NM cable is not allowed above them.

That's what it is like here. Nothing in the plenum can be combustible (not sure if that is only with plenum HVAC return or not) and NM sheathing is. It is a red flag to inspectors.

It is only used for temp lights and power and then scrapped at the end of the project. Inspectors usually make us tKe it all out to pass the overhead electrical inspections.