NM in a commercial setting.

[rc/retired]

Section 320.23 In Accessible Attics

I'm confused. 320 is for type AC cable.
Other than 334.12(A)(2), where's NM-B cable required to be protected in an attic?

Ron

 

[darkov]

It could be installed if building is type III , IV or V construction. Look at the approved plans it shall be stated there.
It has to be protected by 15 min. thermal barrier and that would be 1/2 in gypsum board ( hard ceiling).
As such lay in acoustical ceiling does not qualify as a thermal barrier unless is fire rated.

 

[Little Bill]

If you install NM cable in an attic you have to provide protection against damage. If you install MC cable you don't.

The OP's question DOES NOT ask about protection, it's asking about if NM is allowed in a "stick" built, non-dwelling, structure in the attic. My answer was that it was allowed if it wasn't a dropped ceiling.

I repeat what I said, NM is not permitted above a dropped ceiling in a non-dwelling.

334.12 Uses Not Permitted.
(A) Types NM, NMC, and NMS. Types NM, NMC, and NMS
cables shall not be permitted as follows:
(1) In any dwelling or structure not specifically permitted in
334.10(1), (2), (3), and (5)
(2) Exposed within a dropped or suspended ceiling cavity in
other than one- and two-family and multifamily dwellings

 

[mtnelect]

The OP's question DOES NOT ask about protection, it's asking about if NM is allowed in a "stick" built, non-dwelling, structure in the attic. My answer was that it was allowed if it wasn't a dropped ceiling.

I repeat what I said, NM is not permitted above a dropped ceiling in a non-dwelling.

I checked NFPA 500 under the Day Care / Electrical and it referred back to NFPA 70. So, I stand corrected on NM in attics.

I thank everyone on their patience and comments! ...

 

[James L]

You can't have NM cable above a dropped ceiling in a non-dwelling.

One slight sticking point.

The code says "within" a suspended ceiling
You wrote "above" a dropped ceiling.

I would contend that those are not the same thing.

If you have a stick framed building which does NOT have a suspended ceiling, there isn't any part of that stick framing that could be considered as pertaining to the restiction "within" a suspended ceiling.

So now add a suspended ceiling UNDER that stick framing, and the stick framing is distinct from it. Everything above the eyelets is above the suspended ceiling, certainly not within it

 

[Little Bill]

One slight sticking point.

The code says "within" a suspended ceiling
You wrote "above" a dropped ceiling.

I would contend that those are not the same thing.

If you have a stick framed building which does NOT have a suspended ceiling, there isn't any part of that stick framing that could be considered as pertaining to the restiction "within" a suspended ceiling.

So now add a suspended ceiling UNDER that stick framing, and the stick framing is distinct from it. Everything above the eyelets is above the suspended ceiling, certainly not within it

I would counter with this.
How can you be "within" a dropped ceiling cavity without being "above" the dropped ceiling?

 

[James L]

I would counter with this.
How can you be "within" a dropped ceiling cavity without being "above" the dropped ceiling?

Same as how you can be within a tree house without being above the tree house, within a car without being above it, within a bathtub without being above it.....probably a million others

 

[Seven-Delta-FortyOne]

Last commercial building I did, Inspectigator said it needed a fire rated cover on both sides.

So I could run NM in the walls that had drywall on both sides.

I had to switch to BX or EMT for the crawl space, attic, and of course all the exposed.

However, I’ve done remodels in dozens of commercial buildings where there was miles of Romex in the attics.

When I worked for a GC before going on my own, we wired commercial one story office buildings with NM as well.

So I’m wondering if the inspector on my last one overstated it a bit to include the attic. And maybe the crawl space too, I don’t know.

 

[Little Bill]

Same as how you can be within a tree house without being above the tree house, within a car without being above it, within a bathtub without being above it.....probably a million others

Not a very good analogy. If you're in the ceiling cavity, you are above the dropped/suspended ceiling.
Now if you had a hard ceiling above the dropped ceiling, and you had NM in the attic of the hard ceiling, then the rule wouldn't apply in that case. But you also wouldn't be in the dropped ceiling cavity.

 

[James L]

Not a very good analogy. If you're in the ceiling cavity, you are above the dropped/suspended ceiling.
Now if you had a hard ceiling above the dropped ceiling, and you had NM in the attic of the hard ceiling, then the rule wouldn't apply in that case. But you also wouldn't be in the dropped ceiling cavity.

My point is that there is a structure which stands, completely independent of any components required for a suspended ceiling.

If you don't have a suspended ceiling, that Lumber is still up there. The addition of a suspended ceiling is just that - an addition which stands distinct from the structure that it hangs from

It would be no different from hanging shelves off of those trusses. You have an area within the shelving, then you would have an area above shelving. Two completely distinct areas

 

[Little Bill]

My point is that there is a structure which stands, completely independent of any components required for a suspended ceiling.

If you don't have a suspended ceiling, that Lumber is still up there. The addition of a suspended ceiling is just that - an addition which stands distinct from the structure that it hangs from

It would be no different from hanging shelves off of those trusses. You have an area within the shelving, then you would have an area above shelving. Two completely distinct areas

I'll just leave it here as we aren't making any progress.
Only other thing I would say is to run some NM in a non-dwelling, above, or within the cavity, of a suspended ceiling, and see how inspection goes. I'm not talking about above any hard ceiling that might be there, just directly above the dropped ceiling.

 

[LarryFine]

One slight sticking point.

The code says "within" a suspended ceiling
You wrote "above" a dropped ceiling.

I would contend that those are not the same thing.

If you have a stick framed building which does NOT have a suspended ceiling, there isn't any part of that stick framing that could be considered as pertaining to the restiction "within" a suspended ceiling.

So now add a suspended ceiling UNDER that stick framing, and the stick framing is distinct from it. Everything above the eyelets is above the suspended ceiling, certainly not within it

So, by "within," do you mean inside the thickness of the ceiling tiles?

 

[James L]

So, by "within," do you mean inside the thickness of the ceiling tiles?

No, I mean within the ceiling space.
From the eyelets down to the T-grid, and inside the perimeter of the wall angle.

That's the only way "within" can be properly understood.