Who knows what type nm romex is and type nm-b romex is?

[garylivewireMA]

I hope to find that you all know the answer to this VERY IMPORTANT QUESTION. I find that a lot5 of guys do NOT know this answer. Do you?? Please let me know Gary

 

[bjp_ne_elec]

It's has to do with the temperature rating of the insulation. The NM-B has a higher rating.

 

[celtic]

It's has to do with the temperature rating of the insulation. The NM-B has a higher rating.

How do you know that?
Care to share a reference with the rest of the class?

 

[bjp_ne_elec]

334.112 and FPN. Older Romex that was labeled just NM did not have the 90 degree C rating.

 

[allenwayne]

I`ll venture to say that type nm is listed as moisture resistant while nm-b is not.Southwire list the nm-b as being used in a dry location only, while the FPN says nm is listed as moisture resistant.

 

[bjp_ne_elec]

Doing a search, to try to find out more - and I do remember reading this same info at other references - but here's something I just found.

See the third or fourth Q&A:

http://members.tripod.com/~masterslic/QA.html

I can't find this specifically on like the Southwire site, but I'll find something firmer, just give me a little more time.

Thanks,

Brett

 

[celtic]

NM-B is variant B of NM....

 

[bjp_ne_elec]

Celtic - that's correct - but the search is on to verify that it also means that it has a 90 degree C rating. Don't even think you can get just plain NM any more. The explaination I remember is that they had to go to this, as there were issues with some light fixtures - most needing the 90 degree rating on the insulation.

Brett

 

[bill addiss]

The 1984 NEC required the temperature rating of Type NM Cable to be increased from 60?C to 90?C, to take into account the increased use of thermal insulation in dwellings. The 90?C cable is identified as Type NM-B. NM cable manufactured prior to the 1984 NEC is rated at 60?C and is identified as Type NM.

from:

http://www.nema.org/stds/eng-bulletins/upload/Bull92.pdf


Bill

 

[bjp_ne_elec]

Thanks Bill - I just wanted to have a valid reference. It was in memory, but always nice to site the official ruling.

Thanks

BRett

 

[tom baker]

Next Questions:
What is the complete title for Article 334?
What is NM-C and NM-S
What NEC article is associated with NM-S?
Will the title of article 334 change in the 2008 NEC and why?

 

[cpal]

NMS is a hy brid cable including building wire (power and lighting ) as well as control, voice and data, (cat 5 coax for exampel) I've only handled the type with twisted pair in it same sheat as the insulated conductors.


It was introduced in the 90's (I think) when the smart house technoligy appeard to be an up and coming issue. I have yet to see it installed. Although there is a lot of the multi cable single sheath cable with coax ,cat 5 and voice going in for home entertainment centers.

I guess the other article would be 725 and chapter 8 but I'm not sure where your going with the question,

 

[ryan_618]

The other Article would be 780, although it will be gone in 2008.

The title might change in 2008 because of this, depending on whether or not they delete all references to NM-S.

 

[ryan_618]

NM-C is corrosion resitant.

 

[ptonsparky]

NMC was used in dairy, livestock, bldgs etc - corrosion resistant. It has been a long time since I have seen any.

 

[tom baker]

My point is we only see Art 334 as "Romex".
The company that made NM-s went out of business. It was great idea, the device would signal the panel to turn on the circuit via the signaling cable.
And the 2008 will be shorter by a page or so.
Not sure about the title, would make sense to remove the NMS if the article is gone.

 

[Bea]

Even though it may have a 90 degree rating 334.80 states it must not exceed the 60 degree rating when determining the circuit.

 

[bjp_ne_elec]

Great point Bea.

 

[mdshunk]

Isn't type UF cable dual labeled as type NM-C? I don't have a piece handy to look at, but for some reason that sticks in my mind.

EDIT.. I just went out and checked a piece of UF. It also is marked NMC-B, whatever that means. I guess it's NMC with 90 degree conductors.