Commercial office

[hhsting]

I have type IIIB construction one story commercial office that is wired nm cable. Code does not allow nm am i correct?

 

[rc/retired]

Code does allow it. 334.10

 

[LarryFine]

Except above suspended ceilings.

In new work, I usually mount a J-box on the NM that I poked out of the wall during rough-in, and run MC from there.

In existing work, I sometimes drop NM to the outlet as above, and sometimes drop the MC all the way to the outlet.

 

[david]

I have type IIIB construction one story commercial office that is wired nm cable. Code does not allow nm am i correct?


It must be concealed 334.15 would not apply NMC cable cannot not be exposed in your application

 

[don_resqcapt19]

It is covered by 334.10(3), if the building code required that type of construction.

The use of NM is not based on the actual construction of the building, but based on what construction the building code would permit. If you have a Type I or II building, you can still use NM if the building code would have permitted a different Type of building construction.

 

[Dennis Alwon]

It is covered by 334.10(3), if the building code required that type of construction.

The use of NM is not based on the actual construction of the building, but based on what construction the building code would permit. If you have a Type I or II building, you can still use NM if the building code would have permitted a different Type of building construction.

I did not know that. Thank you

I always read the "permitted to be" to be how it was on the permit. haha

 

[James L]

Except above suspended ceilings.

"Within" suspended ceilings. It's technical, because "within" the suspended ceiling means between the grid and the eyelets where the wires are fastened.

I wired a whole business park in NM, not one stitch of MC. I ran above trusses, which are "above" the suspended ceilings, not "within" the ceilings.

Then I dropped straight down to inside the walls, and that got technical too.

The walls are not "within" the ceiling, either. The perimeter of the ceiling is where the wall angle sits against the wall. There's 4-3/4" of space between two ceilings if there's a sheetrocked wall between them.

 

[david]

"Within" suspended ceilings. It's technical, because "within" the suspended ceiling means between the grid and the eyelets where the wires are fastened.

I wired a whole business park in NM, not one stitch of MC. I ran above trusses, which are "above" the suspended ceilings, not "within" the ceilings.

Then I dropped straight down to inside the walls, and that got technical too.

The walls are not "within" the ceiling, either. The perimeter of the ceiling is where the wall angle sits against the wall. There's 4-3/4" of space between two ceilings if there's a sheetrocked wall between them.

How is what your describing not in an un-cancelled area. Cancelled (not exposed) the area out-side of the cancelled space 15 min. fire protection. Not in an accessible area to protect against physical damage.

Cancelled in walls floors or ceilings, ceiling joist, floor joist and studs are different than roof rafters.

The area must provide concealment of the NM cables

 

[electrofelon]

"Within" suspended ceilings. It's technical, because "within" the suspended ceiling means between the grid and the eyelets where the wires are fastened.

I wired a whole business park in NM, not one stitch of MC. I ran above trusses, which are "above" the suspended ceilings, not "within" the ceilings.

Then I dropped straight down to inside the walls, and that got technical too.

The walls are not "within" the ceiling, either. The perimeter of the ceiling is where the wall angle sits against the wall. There's 4-3/4" of space between two ceilings if there's a sheetrocked wall between them.

Interesting take. Never considered that, but not sure I am convinced. Actually the NEC does not use the word "within" it uses "in". Plus you have 334.10(3) which would require being "concealed" with a 15 minute rating.

 

[LarryFine]

"Within" suspended ceilings. It's technical, because "within" the suspended ceiling means between the grid and the eyelets where the wires are fastened.

So, your take is that the space tops out where the support attachments are?

What would you say if a new ceiling grid was hung from an old ceiling grid?

 

[James L]

Interesting take. Never considered that, but not sure I am convinced. Actually the NEC does not use the word "within" it uses "in". Plus you have 334.10(3) which would require being "concealed" with a 15 minute rating.

It specifically says "within"

 

[James L]

So, your take is that the space tops out where the support attachments are?

What would you say if a new ceiling grid was hung from an old ceiling grid?

above a grid ceiling is another grid ceiling?
NM cannot be "within" either

 

[James L]

334.10(3) which would require being "concealed" with a 15 minute rating.

I think there's an intent there, that NM be concealed and not exposed. Because it specifically mentions ceilings, it clearly does not have grid ceilings in view

 

[david]

keep in mind the 15 min rating is to keep a potential fire source concealed from unconcealed areas to slow down the fire spread, Many suspended ceilings can be rated for 15 min. But now you have to deal with access to the cables for potential physical damage to NM cable that is why suspended ceilings have removable panels to allow access to what's exposed above them

 

[James L]

keep in mind the 15 min rating is to keep a potential fire source concealed from unconcealed areas to slow down the fire spread, Many suspended ceilings can be rated for 15 min. But now you have to deal with access to the cables for potential physical damage to NM cable that is why suspended ceilings have removable panels to allow access to what's exposed above them

Most grid ceilings are at least 1hr rated.
I get the physical damage part. But if there are trusses above, it's next to impossible to find tiles up there. Guys slide them onto the next tile or take them out.

 

[electrofelon]

It specifically says "within"

Interesting, they changed it in 2017 or 2020. 2014 says "in"