History of 334.12 prohibition of NM above suspended ceilings in commercial space?

[kwired]

The restrictions of various non metallic cables has to do with flame spread, fuel load, and other stuff.

This article explains it.

https://www.gpo.gov/fdsys/pkg/GOVPU...VPUB-C13-53eabf2edd0f56d0736d57c2160b67a4.pdf

Didn't go to your link, but does it make sense this is deemed safe for our homes where we sleep at night but is banned or at least restricted in usage because of smoke producing characteristics, flame spread, etc. in other places where people are typically alert while present??

 

[jumper]

Didn't go to your link, but does it make sense this is deemed safe for our homes where we sleep at night but is banned or at least restricted in usage because of smoke producing characteristics, flame spread, etc. in other places where people are typically alert while present??

I do not have a clue.

I just knew a little bit of that info and had that link, prolly from Don also.

IIRC, he is a fireman or something and could answer better than I.

 

[shortcircuit2]

Romex is just a step above extension cords IMO and the outer sheath provides little protection to the conductors.

At least with MC Cable you have an outer metallic sheath that provides abit more physical protection.

I'm not a supporter of the Mass amendment to use Romex above suspended ceilings and I wish they would remove the amendment. How many of us have opened a dropceiling in an older building here in Mass and said OMG...look at this rats nest of Romex. Its ugly up there.

City of Chicago got it right...no Romex available in Box Stores around there.

 

[RICK NAPIER]

I believe NJ amended the Code to remove 334.12(A)(2) in its entirety.

-Hal

It was removed but be careful since 334.10(3) was not changed so unless it's a fire rated assembly you still can't use it in other than a dwelling.
334.10 Uses Permitted. Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following, except as prohibited in 334.12:
(3) Other structures permitted to be of Types III, IV, and V construction. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material
that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.

 

[roger]

I sleep well even knowing my home is wired with NM. If you look at the trillions of (or more) circuits wired in NM verses the number of fires actually (not falsely reported on the news) started by bad NM or it's installation it is an extremely safe wiring method.

Roger

 

[kwired]

I sleep well even knowing my home is wired with NM. If you look at the trillions of (or more) circuits wired in NM verses the number of fires actually (not falsely reported on the news) started by bad NM or it's installation it is an extremely safe wiring method.

Roger

I sleep fine in my home myself, I wired it new and know what was done and was done before AFCI was required and that doesn't even bother me, but could easily have concerns for shoddy work on any other wiring method as well.

But the question was why is it safe in our homes but not so safe in other places?

 

[norcal]

Would be interesting to see statistics from other countries VS the US on places of assembly & the wiring methods employed, when I was in Germany noticed the wiring in a lot of places was not much above flexible cord in terms of construction & even was used in a church.

 

[kwired]

Would be interesting to see statistics from other countries VS the US on places of assembly & the wiring methods employed, when I was in Germany noticed the wiring in a lot of places was not much above flexible cord in terms of construction & even was used in a church.

They also use (not sure the requirements though) RCD protective devices, we eventually got stuck with AFCI's, there are many that feel the RCD is overall better approach.

 

[peter d]

The NM cable restriction above "commercial" suspended ceilings is an absolute joke, at least in my state. Why, you ask? Because above that same suspended ceiling is a network of PVC drain and PEX pipes and sometimes CPVC fire protection depending on the occupancy. If it's really about "smoke load" that would all be banned as well. These gross inconsistencies are why the NEC lacks so much credibility in so many areas.

 

[peter d]

Romex is just a step above extension cords IMO and the outer sheath provides little protection to the conductors.

It's still a safe and functional wiring method. There are literally hundreds of thousands of commercial buildings wired with NM cable in New England (not just Mass.) with zero problems related to NM cable. Once upon a time every Stop and Shop supermarket was wired with NM cable before the code changed. Oh, the horror. :roll:

At least with MC Cable you have an outer metallic sheath that provides abit more physical protection.

Why this obsession with physical protection? If it's 20' up run in bar joists, nothing is going to damage it.

I'm not a supporter of the Mass amendment to use Romex above suspended ceilings and I wish they would remove the amendment. How many of us have opened a dropceiling in an older building here in Mass and said OMG...look at this rats nest of Romex. Its ugly up there.

And you've never seen a rats nest of MC cable? :huh: I see MC cable horrors constantly. You really think changing the code will make a difference? :lol::lol: Wiring method is irrelevant, these kinds of messes get created from poor installation practice, not the kind of cable in use.

City of Chicago got it right...no Romex available in Box Stores around there.

Lol, ok.

 

[giovanni0502]

I think it is a valuable rule. As an inspector I go to a lot of fires, both commercial and residential. It is common to watch the fire inspector track the start of the fire to a romex staple nailed too hard. Now whether it is from initial installation, combined with building movement, or someone hung something from romex or hit it carrying something (these are often started in the basement) it is proof that while NM is cheap and fast, it is not durable. I don’t think the rule pertains 100% to plenum and smoke considerations. I think durability and safety are also a factor. Putting NM cable in a drop ceiling in a commercial building absolutely subjects it to more risk for pulling on it from electricians moving troffers, other tradesman working in the ceiling, and maintenance men doing daily repairs. Also lets be honest, pride is a tool that not everyone carries. I see daily how guys sling MC as the crow flies, run ugly conduit runs, and place j-boxes in obscure places just because it is faster and “they see no reason to waste time making everything pretty”. Therefore, rules like this, in my line of work, are beneficial.


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[kwired]

I think it is a valuable rule. As an inspector I go to a lot of fires, both commercial and residential. It is common to watch the fire inspector track the start of the fire to a romex staple nailed too hard. Now whether it is from initial installation, combined with building movement, or someone hung something from romex or hit it carrying something (these are often started in the basement) it is proof that while NM is cheap and fast, it is not durable.

Unless conductor insulation gets damaged, that probably doesn't start a fire. When I see fires that started in wiring usually involves overheated termination points.

I don’t think the rule pertains 100% to plenum and smoke considerations. I think durability and safety are also a factor. Putting NM cable in a drop ceiling in a commercial building absolutely subjects it to more risk for pulling on it from electricians moving troffers, other tradesman working in the ceiling, and maintenance men doing daily repairs.

Why you have so much activity going on in these ceilings, especially moving of troffers? Most of the troffers I see get installed and never get touched for years other then to relamp or change ballast - and they don't ordinarily get "moved" to do those tasks.

Also lets be honest, pride is a tool that not everyone carries. I see daily how guys sling MC as the crow flies, run ugly conduit runs, and place j-boxes in obscure places just because it is faster and “they see no reason to waste time making everything pretty”. Therefore, rules like this, in my line of work, are beneficial.


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Those things do make some differences at times. If running something through ceiling after ceiling has been finished, you very well may see lower quality work then you see for things that were installed before ceiling was installed. Nice neat raceway installs for what was put in before ceiling was dropped - that new circuit installed 3 years later is in MC cable, maybe not secured quite as often as it should be, and run "as the crow flies" to it's destination.

 

[peter d]

I think it is a valuable rule. As an inspector I go to a lot of fires, both commercial and residential. It is common to watch the fire inspector track the start of the fire to a romex staple nailed too hard. Now whether it is from initial installation, combined with building movement, or someone hung something from romex or hit it carrying something (these are often started in the basement) it is proof that while NM is cheap and fast, it is not durable. I don’t think the rule pertains 100% to plenum and smoke considerations. I think durability and safety are also a factor. Putting NM cable in a drop ceiling in a commercial building absolutely subjects it to more risk for pulling on it from electricians moving troffers, other tradesman working in the ceiling, and maintenance men doing daily repairs. Also lets be honest, pride is a tool that not everyone carries. I see daily how guys sling MC as the crow flies, run ugly conduit runs, and place j-boxes in obscure places just because it is faster and “they see no reason to waste time making everything pretty”. Therefore, rules like this, in my line of work, are beneficial.

I live in the land of "NM cable in commercial buildings" aka New England and I simply don't see any evidence to support what you describe. I firmly believe that very few fires are actually caused by faulty premises wiring.

 

[romex jockey]

Don G would be better with the stats.

My own experiences standing next to fire chiefs ,looking into a smoking cellar hole claiming it 'had to be 'lectrical, cuz no one wuz home' have tainted me....

~RJ~

 

[texie]

Romex is just a step above extension cords IMO and the outer sheath provides little protection to the conductors.

At least with MC Cable you have an outer metallic sheath that provides abit more physical protection.

I'm not a supporter of the Mass amendment to use Romex above suspended ceilings and I wish they would remove the amendment. How many of us have opened a dropceiling in an older building here in Mass and said OMG...look at this rats nest of Romex. Its ugly up there.

City of Chicago got it right...no Romex available in Box Stores around there.

Well, I'm not really a big fan of NM wiring methods but there is not anything inherently wrong with it and it has its place. But I can assure you the age old prohibition of it in Chicago Land has nothing to do with safety.

 

[kwired]

I live in the land of "NM cable in commercial buildings" aka New England and I simply don't see any evidence to support what you describe. I firmly believe that very few fires are actually caused by faulty premises wiring.

Depends on what "faulty" means I guess. I don't think you find NM cable suddenly bursting into flames, you almost never see it even melt down other then within first few inches of a weak connection. Use 12 AWG for a circuit that draws near 50 amps - even other methods are likely to experience some overheating issues. Still seems there is a good chance of a connection being the potential fire starting point over just starting in the middle of a run.

 

[david]

What i do here from tenants in commercial spaces is, I had to hire an electrician because i was told i couldn't use romex.

If nothing else it keeps everyone who can turn a light switch on thinking they could do it them selves

 

[roger]

I firmly believe that very few fires are actually caused by faulty premises wiring.

And I agree.

Roger

 

[kwired]

What i do here from tenants in commercial spaces is, I had to hire an electrician because i was told i couldn't use romex.

If nothing else it keeps everyone who can turn a light switch on thinking they could do it them selves

NM cable or otherwise, and even up to 20 years ago, some of those same people have occasionally mentioned to me before: "I though you couldn't use 14 gauge wire anymore?" My bet is they were the type that runs 12 AWG on 20 amp circuits, but ran 14 AWG for switch loops on those circuits, were told they can't do that at some point and interpreted it as 14 AWG is prohibited for everything.

 

[peter d]

Depends on what "faulty" means I guess. I don't think you find NM cable suddenly bursting into flames, you almost never see it even melt down other then within first few inches of a weak connection. Use 12 AWG for a circuit that draws near 50 amps - even other methods are likely to experience some overheating issues. Still seems there is a good chance of a connection being the potential fire starting point over just starting in the middle of a run.

I concur, but again I believe even those instances that cause an actual fire to be quite rare. Usually a lose connection of some sort will make itself known, which in my world is one of four things 99% of the time - faulty wire nut splice, faulty backstab, faulty connection to bus bar, and faulty breaker to bus stab connection. In the case of splices, usually the damage is contained to the junction box.