334.10(3) requirement

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bphgravity

Senior Member
Location
Florida
This issue was discussed on another topic, and now I have a similar issue.

I have a commercial building (Type V unprotected) with an open truss ceiling and an insulated drop ceiling. There is no drywall or other finish between the drop and the roof assembly.

Can NM cable be used in the area above the drop in the open truss area (not in the drop area itself) and comply with 334.10(3)?

Do insulated ceiling tiles provide a "15 minute finish rating"? (The drop is not a fire rated assembly)
 

kbsparky

Senior Member
Location
Delmarva, USA
NOT in our area. Unless you have some sort of fire-rated ceiling on the bottom of those trusses, effectively separating the "attic" space from the "living" space.

We had a similar building here, with wood-truss construction. Since they installed a barrier under those trusses, the space above them was fair game when it came to installing type NM cable. Any walls that met up with the "attic" area could also be wired with NM feeders brought down from the attic.

The wiring contained in the area above the suspended ceiling, and the adjoining walls had to be installed in EMT conduit, or MC cable to comply with the NEC.

Funny thing, this so-called requirement. It is one of those "political" rules that should be abolished, and really has nothing to do with actual safety, IMHO.
 

volt102

Senior Member
Location
New Hampshire
kbsparky said:
NOT in our area. Unless you have some sort of fire-rated ceiling on the bottom of those trusses, effectively separating the "attic" space from the "living" space.

Is the attic accessible?
Effectively seperating them into to seperate buildings with only a fire rated ceiling?

Jim
 

bphgravity

Senior Member
Location
Florida
Thanks for the comments. I have the issue figured out. The ceiling tile installation is not a listed assembly and only has a flame spread/smoke developed rating. The 15 minute rating is simply not there so NM can't be installed.

I would like to better understand the reason for this requirement.
 

bphgravity

Senior Member
Location
Florida
No, the cables are still accessible by removing the tiles. The cables simply need to be concealed within the space between roof and the ceiling. Accessibility is not issue.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
Concern i assume is in case of fire.Depending on occupancy this may or maynot be an issue.My thinking says if all are not out in under 5 minutes we have a problem.
 

volt102

Senior Member
Location
New Hampshire
Accessibility is the issue?

This space between the roof and the ceiling, it is accessible. (You had said that these are open truss ceilings) If I can access that attic, then it does not meet the requirement of having to be concealed.

Jim
 

sandsnow

Senior Member
Finish rating is often confused with fire resistive rating. Although related, they are two different tests.

Simply it is the time it takes the non-fire side to reach 250'F under test conditions. Smoke and flame spread as Bryan said is not an indicator.

Finish ratings are not used in conjunction with ceiling tile. They are used in conjunction with material such as plywood or drywall mounted to wood framing members.

See these links:

http://www.awc.org/Publications/dca/dca4/DCA4.htm
click on Use and Application.

http://www.nema.org/stds/fieldreps/faqs.cfm#outlet
click on Outlet Boxes
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Hypothetically, if the ceiling tile did meet the 15 min. rating, then would the NM cable be allowed?

I'm not sure the word "ceiling" in 334.10(3) was meant to include the entire attic space. If that is correct, the NM still wouldn't be concealed in a "ceiling". So I am inclined to agree with Volt102 that the NM has to be concealed from the attic. (But IMO it doesn't matter if the attic is accessible or not).

Steve
 

volt102

Senior Member
Location
New Hampshire
The code states that cables shall be concealed. Then it states that it must be done within walls, floors, ceilings.

Concealed. Rendered inaccessible by the structure or finish of the building.

Romex cannot be installed exposed in other then a residential setting...

So once again, if it is accessible(in the whole ceiling, above the drop and in the attic that requires a scuttle) it is not code compliant in the situation decribed by the OP...

Jim
 

bphgravity

Senior Member
Location
Florida
Ahh, I see what you are saying Jim. Very interesting.

I have only been looking at this from the viewpoint of the interior space. I am under the impression that if the envelope or membrane of that interior area has the required rating on the floor, walls, and ceiling, NM is permitted on the other side of that membrane or envelope.

There is where the building codes don't read the same as the NEC. The NEC seems to be coming from the perspective that exposed and concealed are opposite in that exposed is accessible and concealed is not. Where as the building code doesn't care what the rating of the attic space is as it is not "finished".

So, based on the language used in the NEC, I can't tell if the concern is with how accessible the NM cables OR is the concern with a fire spreading into a concealed location from the other side of a finished area??????
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
So......if the bottom of the trusses were covered with drywall giving a 15 min. rating, and the NM was installed below that drywall, the NM would be concealed from the attic space.

And lets also say the ceiling tile has a 15 min. rating (I don't know if you can even get a rated ceiling tile system, but say you can.) Then the NM still isn't allowed because the ceiling tile does not conceal the NM cable. It may hide it from view, but since the cable is still accessible, it is not concealed.

Anyone agree or disagree?

Steve
 

sandsnow

Senior Member
It would have to be concealed above the drywall ceiling in "other" structures. 334.10(3)

Above a suspened ceiling you cannot have an "open run". Whatever "open run" means? I assume you could protect with guard strips, but at that point why bother.
So as long as you can convince the inspector or AHJ that you don't have an "open run" and the tile has 15 minute finish rating, then you are ok. Hypothetically speaking.

I have not run into anyone proposing to run NM in other than dwelling yet. So, I have really not had to address the issue. Most interpretations I've read, say that NM is not allowed above suspended ceiling period.

I can drop a ceiling using steel or wood framing members. I can also suspend a ceiling using metal framing members. In both cases drywall is used as a finish material. I do not think that the intent was to prohibit NM above those instances, but I could be mistaken
 

radiopet

Senior Member
Location
Spotsylvania, VA
Hey all,

I think the revision to the 2002 Code namely 334.12(A)(1) made it clear that if the area above the ceiling in a other than one and two family or multifamily dwelling is accessible ( below or above ) it is considered open and NM is not allowed.

So to me.....the idea is IF you can access the area above the ceiling either from below or above AFTER the construction and finish of the design....that IF you can get to it freely even with an access and so on...it would be considered a " Open Run of Cable " and 334.12(A)(1) would not allow it...even if NM is approved for a "V" class consruction.

Again...if the ceiling is normal gypsum board and no access above down TO the wiring as well....I would consider it concealed and not a problem...a simple change by the designer can effect this.....like changing from a gypsum to a dropped ceiling...would violate the ability to use NM in this case....because the tiles are removeable .....and likewise changing from a dropped ceiling to a finished gypsum would then allow it's use.....provided again no access to the space from above or below the finished area....

just my views on it....:)
 
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