Are there any places at all where NM can be run in Commercial Bldgs? I looked it up but not sure where if at all they are saying you can. I never have never seen it run.

Forgetting local amendments and customs the NEC does not prohibit the use of NM in commercial spaces. It does prohibit NM from the space above a suspended ceiling in a non-dwelling unit.

The NEC limits the use of NM by building type. That is the type of construction not by the use of the building. (For the most part)

Here in my area you will find many commercial buildings wired with NM. It is used for 480 as well as 120.

We also have a local amendment which allows the use of NM above the suspended ceiling of non-dwelling units.

[This message has been edited by iwire (edited 05-04-2006).]

So you can use it in any commercial building except for above a drop ceiling? Why wouldn't more contractors use NM then?

I see it everywhere I go in the C store world, last code update class I had the head State inspector was allowing it above suspended ceilings also. Not sure if the they amended the code or he just allows though??

No, you can use it in buildings that are type III, IV or V construction. You can't use it in type I or II.

walrus, there was a state amendment to that part of 334 to allow the use of NM above a dropped ceiling

Ryan- You are right about the Class I & II Construction if you use the '05 code but under the '02 you could use it in Class I & II construction because it was not specifically prohibited in the '02.

[This message has been edited by George Little (edited 05-04-2006).]

George, I'm not following you. Type of construction was a change to the 2002 NEC, not the 2005.

Ryan- You are correct in that the type of construction wording came in in the '02. BUT- The wording only said that Class III, IV and V construction permitted NM cable with no floor limitation. This was challenged at our State Appeal board and it was decided that since it was not shown as "Uses not Permitted" that it would be allowed in all types of construction. In the '05 code they nailed it by the wording in 334.12(A)(1). Jeff Sargent and a few other noteables were involved with the State decision. I think the code panel goofed in '02 and they corrected it in '05. The problem is making a "Uses Permitted" all inclusive and there in lies the loop hole.
I don't know if you knew it or not but Michigan has for at least 25 years allowed NM cable with no limitations on structure type or floor height. There track record is in tact and they are not burning down any high rise buildings due to NM cable. So until they see a convincing arguement to disallow NM cable, we will be using it by amending out wording that would prohibit it's use.

D** Typo's

[This message has been edited by George Little (edited 05-05-2006).]

How is type lll, lV, or V different than l or ll.

Type I and II have a higher fire resistant rating. There is a table in the '02 NEC as I recall, that give the fire rating and materials permitted for each Type of construction. Type I being the most fire resistant.

In a nutshell...

Types I and II are noncombustible (steel and concrete only). Type III is a limited amount of wood (such as masonry walls and wood trusses). Type IV is heavy timber (nearly nonexistent in most of the country). Type V is wood.

See Annex E in the back of the NEC.

When you do the math it turn out that when you factor in the labor and material for the wiring of a building the cost difference is about 20% less for NM cable. Now when it's a midrise or highrise building that's a fair piece of change. Also, NM cable is not usually the cause of fires. If NM cable causes fires more than other wiring methods maybe we shouldn't be wiring our homes with it. That's where we sleep DUH??

George Little,
That just material cost, what about the less time to in stall it too.

I'm not sure how many stories are required for a building to be considered a high rise, but under the IBC the tallest building that can be built using type III, IV, or V construction would be 5 stories. With a sprinkler system, that would increase to 6 stories. That is for an office building. With merchantile or residential occupancies, the limit would be 4 stories with a sprinkler increase to 5 stories. Those figures are for type III and IV. The limits for type V are less. Any buildings taller than these limits would need to be type I construction, which would prohibit the use of NM cable.

Other building codes will have story limits for type III, IV, and V construction in the same ball park.

Ryan,

If construction types One and Two are the least combustible why isn't NM cable permitted? I hope this isn't too dumb of a question. I've had difficulty understanding construction types as it applies to permisson to use NM cable since it was adopted by the NEC.

Frank

"One and Two are the least combustible why isn't NM cable permitted?" NM is combustable... In the sense of fire fuel and travel, and smoke load of a fire. Is my understanding of it... The NEC is written by the NFPA....

Do a little experiment:
Take a piece of NM, and a piece of MC 2' long, staple them to a wall verticaly, and apply a torch to them at the bottom. The one that wins the race to the top looses.

IMO the old "3 story rule" was much easier to interpet: (pre 2002 from the 99' NEC)

That was real simple..... 3 stories OK, 4 stories NOT OK. (Around here 4 stories also triggers the madatory installation of sprinklers.)

Localy NM is limited as follows with ammendments to the 2002 CEC/NEC:

So if you have (like often is the case here) commercial on the lower floors, and residential above. It would be MC and pipe on the commercial and common areas of that space, and possibly NM in the residential, depending on the other limits. The commercial portion of the building is one building type, the residential portion another. So often the buildings are concrete, steel studs, sprinklers and fire rated envelopes of the space. Often a concrete deck on top of it, then a wooden structure built on top of that for the residential portion.

I suppose one could build an airplane out of beer cans- but that's not really what the cans were intended for.

In a like manner, Romex was never intended for use in anything but the most simple of installations, such as homes were in the '30's.
(That's right- Romex dates from the '30's).

Let's keep in mind the DIS-advantages of using Romex:

- You're stuck with the provided colors. This becomes an issue with switch legs;

- You're stuck with the provided quantity of wires (so you get to carry multiple rolls);

- You're stuck with one wire size per cable. If your final location is one where you need different sizes, you get to pull multiple cables;

- You're limited to two cables (circuits) per connector; when entering a panel from the ends, you quickly run out of places to pu those connectors; and,

- Every cable has its' own ground wire. Panels get crowded pretty quickly!

I'm not trying to 'bash' the stuff; it's just that on the typical commercial or industrial job, I see nothing but MORE work using it rather than pipe.

Sure, running pipe takes more tools than a stapler and a pair of snips- but you are able to pull additional wires later (even replace a junction with a sub-panel if you desire), and get additional protection as well.

So types 111, 1V & V - NM is permitted? Meaning if there is wood construction NM is ok residential or commercial?

Read carefully what the clause in Uses Not Permitted says: "(1) In Type I or II construction unless permitted to be Types III, IV, or V construction." (Emphasis added.)

So to answer the question of why you can use NM in a wooden building, but not in a building built from things that don't burn, is this: When the building is required to built from highly fire-resistive materials, you cannot use NM. If the building is not required to be highly fire-resistive (even though it may be built from fire-resistive materials), then (in many cases) NM is OK. The idea is that there is a hierarchy of how critical a building is, and critical buildings must be built so they won't burn down, and so that the electrical system is as safe as practical.

(I note that it appears that our homes, our bedrooms, are in the "let the danged thing catch fire and burn down" category . )



[This message has been edited by SolarPowered (edited 05-17-2006).]

Well I certianly agree with the comments made by Reno about the use of pipe and wire for commercial and industrial wiring and with SolarPower that we can wire a Class I & II building with NM cable under the conditions mentioned. I do have a problem with the mind set that NM cable is a dangerous wiring method. The plus side of using NM cable are left out of this thread and that's a mistake. NM cable is not the cause of fires any more than any other wiring method. If it were a dangerous wiring method I think we would not sleep well at night in our homes. I'm sure Reno's home is in NM cable instead of pipe and wire, also SolarPowered probably has NM cable in his home. Unless one lives in the Chicago area they probably have NM cable in their homes. The cost is also a factor with NM, MC or AC cables. The primary reason for using a cable wiring method would be the savings on labor and material. Cable wiring methods are not dangerous!! I've been told that this amounts to about a 20% savings. That's not chump change when you are talking a huge project and the cost of labor and material today. IMHO

Edited due to typos, du to not awake yet

[This message has been edited by George Little (edited 05-17-2006).]

It would seem to me masonry and metal would be non-combustionable and you could use romex?

I think they are going the other way. If a type 1 and 2 building is very fireproof they don't want to compromise that with what some think is an inferior wiring method.
I tend to agree with George on this when he says NM is a pretty safe way to wire things but old traditions die hard.
I do believe wire in pipe is a lot easier to modify and they modify commercial a lot more than your average home so they have reasons beyond safety in mind when they select EMT.

I checked with the city inspec here in AZ and they said no NM in commercial, its all metal in commercial buildings. That my be their own code. The code book doesn't make it real clear to me. So I'll do everything in conduit like the city wants.

In my experience the AHJ decides the issue. Period.

Normally, ALL commercial is non-Romex.

Who is to say that a subsequent tenant won't use a soft lid even if Romex is above?

Residential is treated so differently because the owners/tenants live there and can find the escape instintively.

Commercial is treated to such a different standard because experience shows that when fire occurs most there do not know what is the best escape.

A perfect example would be the Rhode Island night club tragedy wherein escape routes all over the club were not used because none of the patrons knew that they were within x feet of an exit. Everyone tried to get out through the original entry. This is a pattern common to all commercial fires. That is why the bar is set so high in commercial.

The bar is set even higher in utility and chemical plants. The NEC is a slacker compared to the standards demanded there. This time the issue is pure economics. Assets, not people, must be saved. They are too costly to lose.