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#98129 05/17/06 02:39 AM
Joined: Jul 2004
Posts: 625
S
Member
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 [Linked Image]. )



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

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#98130 05/17/06 08:52 AM
Joined: Jan 2004
Posts: 1,507
G
Member
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 [Linked Image]

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


George Little
#98131 05/17/06 11:04 AM
Joined: Aug 2001
Posts: 545
A
aldav53 Offline OP
Member
It would seem to me masonry and metal would be non-combustionable and you could use romex?


The Golden Rule - "The man with the gold makes the rule"
#98132 05/17/06 01:40 PM
Joined: Jul 2004
Posts: 9,923
Likes: 32
G
Member
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.


Greg Fretwell
#98133 05/17/06 03:48 PM
Joined: Aug 2001
Posts: 545
A
aldav53 Offline OP
Member
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.


The Golden Rule - "The man with the gold makes the rule"
#98134 06/09/06 02:28 AM
Joined: Jun 2004
Posts: 1,273
T
Member
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.


Tesla
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