nm cable in suspended ceilings

[bulldog]

I was looking at job bid and it showed nm cable in an suspended ceiling. The building is commercial. I read that nm cable can only be used in single and multifamily units with a suspended ceiling. Is their something aI am missing?

 

[ryan_618]

Re: nm cable in suspended ceilings

You are not missing anything. NM cable cannot be used in the suspended ceiling you speak of.

 

[earlydean]

Re: nm cable in suspended ceilings

334.12(A)(1)

 

[jimwalker]

Re: nm cable in suspended ceilings

It was in 96 and i believe 99
We wired an office building using nm in walls and above the sus ceiling, even to feed the lay in 2 x 4 fixtures

 

[delfa]

Re: nm cable in suspended ceilings

We have been using NM cable to wire offices if the occupancy rating, between fire walls, was below a certain number. I forget what that magic number came out to. It's been passing inspection. Are we doing it wrong?

 

[jimwalker]

Re: nm cable in suspended ceilings

In our case we were still on 99 and the inspector wasn't too happy but had to take it.He also cautioned us that when 2002 kicked in it wouldn't be ok.So depends on what your running on.I for one don't understand how nm can be fine in a house or even multifamily but dangerous in an office building that no one is sleeping in or even occupying for more than maybe 50 hours a week.
Doing this bothered me but wasn't my choice.

[ December 25, 2003, 01:12 PM: Message edited by: jimwalker ]

 

[ryan_618]

Re: nm cable in suspended ceilings

Delfa: The NM article has changed dramatically in the past few years. I would not be comfortable asnwering your question without knowing which code you are on. More info please?

 

[pierre]

Re: nm cable in suspended ceilings

Jim
There were smoke tests performed and the results were reviewed by the CMPs. I believe the 2002 version permits this type of installation in dwellings as opposed to other than dwellings because of the time it will take to exit a commercial building as well as the number of occupants of the commercial compared to a dwelling during a fire. Panic of the larger number of persons can be contagious.
Dwellings are generally smaller and easier to exit than commercial type buildings. JMO

Pierre

 

[jimwalker]

Re: nm cable in suspended ceilings

PIERRE i am partially in agreement.I know the code is bottom line, but there are often some very old firetrap buildings that have poor families packing 2 bedroom units with 20 persons and some of these are 3rd floor with 1 exit.If NM is not safe above suspended ceilings in an office with maybe only 6 employees that are awake ,why allow it were 20 might be asleep.
The idea of NM in homes has bothered me for years.There are far safer wiring methods for homes but not used because of cost.

 

[pierre]

Re: nm cable in suspended ceilings

Jim
I understand your concern and I believe most here have the same concern, but your issue is a building code issue, the number of persons in a dwelling unit are usually much less than in an office environment. Also the INS would be involved with 20 or more to an apartment, we have some of the same problems where I live.

Pierre

 

[jimwalker]

Re: nm cable in suspended ceilings

Delfa if your AHJ is still using 99 NEC your still ok other than the # of peeps.Watch out when they adopt 02

 

[peter d]

Re: nm cable in suspended ceilings

The idea of NM in homes has bothered me for years.There are far safer wiring methods for homes but not used because of cost.

Huh? Am is missing something here? What is unsafe about NM cable?

 

[iwire]

Re: nm cable in suspended ceilings

Originally posted by jimwalker:
The idea of NM in homes has bothered me for years.There are far safer wiring methods for homes but not used because of cost.

Would you like to try to back that up with some facts?

Of course you own house must be wired with RMC right?

 

[roger]

Re: nm cable in suspended ceilings

There is probably more NM in place in this nation than all other wiring methods combined, and percentage wise, there are probably less fires truly associated with it.


This was even true before we were given the "godsend" AFCI to protect us from parallel arcs. :roll:


Roger

[ December 26, 2003, 08:55 PM: Message edited by: roger ]

 

[ryan_618]

Re: nm cable in suspended ceilings

I find it interesting that this post has evolved from suspended ceilings to safety of NM cable. The two are closely related when you read the 2002 ROP's. Notice that the provision for prohibiting NM in suspended ceilings is a "trade-off" for the use of it in buildings greater than three stories. The fact of the matter is, the 2002 NEC is less restrictive than the 99 in use permitted/uses not permitted.

I think if you were ask the CMP of article 334/336 and the NFPA, they would say that type NM cable has a pretty good track record.

I see nothing wrong with it when installed to the minimum code/standards.

 

[roger]

Re: nm cable in suspended ceilings

Ryan, you are absolutly right in that it was a trade off to the metalic cable and conduit industry. Nothing more, nothing less IMO.

Roger

 

[iwire]

Re: nm cable in suspended ceilings

Originally posted by ryan_618:
Notice that the provision for prohibiting NM in suspended ceilings is a "trade-off" for the use of it in buildings greater than three stories.

Originally posted by roger:
Ryan, you are absolutely right in that it was a trade off to the metallic cable and conduit industry. Nothing more, nothing less IMO.

I was going to point this out but I did not have the facts.

It is sad that it was a trade off and had little, if anything to due with a real safety issue.

I can be happy to live in MA where NM is still allowed in suspended ceilings, even though 95% of the time I run MC.

[ December 27, 2003, 06:52 AM: Message edited by: iwire ]

 

[electricmanscott]

Re: nm cable in suspended ceilings

The idea of NM in homes has bothered me for years.There are far safer wiring methods for homes but not used because of cost.

Jim enlighten us please.

[ December 27, 2003, 11:12 AM: Message edited by: electricmanscott ]

 

[jimwalker]

Re: nm cable in suspended ceilings

Would think that thhn in EMT would have far less likely hood of getting damage by staples ,screws,or getting pulled against steel truss plates .And if they did the chance of a fire or shock would be greatly reduced.If NM was as good as EMT then we would allow it in offices.

 

[ryan_618]

Re: nm cable in suspended ceilings

Jim: It is allowed in offices. Read "uses permitted" and "uses not permitted".