ECN Forum
Posted By: gfretwell What is NMC? - 06/15/05 05:40 PM
Since we a talking about obscure wiring methods is anyone using NMC?
When I started looking at the wire manufacturers they shunt me off to UF.

My wild guess is that NMC is NM with a plastic wrapper instead of the paper so it would not wick up water but that is just a guess. I can honestly say I have never seen it and none of the supply houses I have visited stock it.
Posted By: Ryan_J Re: What is NMC? - 06/15/05 09:13 PM
I also have never seen it. I have never seen NM-S either.
Posted By: Larry Fine Re: What is NMC? - 06/16/05 04:35 PM
I believe the "C" designation refers to corrosive environments.

[This message has been edited by Larry Fine (edited 06-16-2005).]
Posted By: nwelectric Re: What is NMC? - 06/16/05 11:54 PM
The C refers to the temperature rating of the cable.

Frank
Posted By: wa2ise Re: What is NMC? - 06/17/05 02:49 AM
Years ago back in college, homework done, had a few hours to kill poking around in the engineering library. Found a book on electrical wiring codes (don't remember which book, it even might have been from Europe) and thumbed thru it. One wiring method described was "Mineral Insulated Cable". If I recall correctly it consisted of a metal pipe and two (or more) conductors. Insulation was some sort of high temperature material, which didn't like moisture. You needed special connectors (compression?) and white and black insulating tubing to slip over the wires so you could wire things up in a box (wires were bare away from the mineral insulation in the pipe). Also sealent to keep moisture out. Maybe similar to what is done with heating coils on electric cooktops?

Is this something that is obsolete, or is likely found in nuclear power plants or other exotic environments? Maybe a steel mill?
Posted By: renosteinke Re: What is NMC? - 06/17/05 04:08 AM
wa2wise, please see the non-US forum for a discussion of "pyrotex."
Posted By: gfretwell Re: What is NMC? - 06/17/05 05:48 AM
Bob teased the home inspectors with this the other day.
http://www.sesco-ge.com/pd_pyrotenax.htm
Posted By: kale Re: What is NMC? - 06/17/05 09:48 PM
NM Non-metallic sheathed cable, braid or plastic covered. For dry use, 60°C.

NM-B Non-metallic sheathed cable, plastic covered. For dry use, 90°C.

NMC Non-metallic sheathed cable, plastic or neoprene covered. Wet or dry use, 60°C, and corrosive applications.

According to NEMA, "Types NMC and NMS are not commercially available, but type UF-B can be substituted for NMC. Type NMS is a construction consisting of NM-B and data/communications cables."


[This message has been edited by kale (edited 06-17-2005).]
Posted By: iwire Re: What is NMC? - 06/17/05 10:07 PM
wa2ise regarding MI cable.

Quote
Is this something that is obsolete, or is likely found in nuclear power plants or other exotic environments? Maybe a steel mill?

Not obsolete in the least.

It is commonly installed as feeders for emergency circuits.

I saw a good video of it under test, it survived a couple of hours directly in a large (huge) flame all the while it was still conducting power just fine.

Here is a photo of MI in a Hospital.

[Linked Image from nachi.org]

And here is a close up of the connectors

[Linked Image from nachi.org]

This is single conductor MI that is why you see it in groups of four phases A, B, C, and N.

The brass plate is needed to comply with 300.20(B).
Posted By: Ryan_J Re: What is NMC? - 06/17/05 10:30 PM
Great pics Bob! I'm going to have to save those for some presentations. [Linked Image]
Posted By: iwire Re: What is NMC? - 06/17/05 10:38 PM
Thanks Ryan, I am sad to say this particular job is not our work.

I was in this room for some other work and had to grab some pics.

Some of these feeders run hundreds of feet through suspended ceilings and where installed while the hospital was already up and running.

It had to be a real pain in the rear, this stuff bends about as easy as a solid copper bar.
Posted By: Trumpy Re: What is NMC? - 06/17/05 11:23 PM
Yeah we had a bit of a discussion on it here .
Them pictures are flash, Bob.
However, I've never seen Pyro bundled together like that before under saddles.
That could be a problem if the cables vibrate against each other.
I was always told to saddle them individually.
I did quite a bit of work with this stuff during my apprenticeship as an Electrician.
Anyone that thinks that this stuff is easy to work with needs to see a doctor. [Linked Image]
Posted By: iwire Re: What is NMC? - 06/17/05 11:35 PM
Evening Mike, or is it mourning for you?

Quote
I was always told to saddle them individually

That could be interpreted as a NEC violation unless the saddles where non-magnetic.

NEC
Quote
300.20(B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.

Have you ever found the separate saddles warm or hot where used individually?

Bob
Posted By: Trumpy Re: What is NMC? - 06/18/05 12:11 AM
Gidday Bob,
Yes, I see what you mean, Eddy currents can be a worry.
Non-ferrous (Brass normally) saddles are usually used here.
BTW, it's Saturday afternoon here. [Linked Image] [Linked Image]
Posted By: renosteinke Re: What is NMC? - 06/18/05 12:49 AM
Thanks, Kale, for the info. What was your source? It probably has lots of other things I don't know in it!
Posted By: shortcircuit Re: What is NMC? - 06/18/05 12:50 AM
I found this during my barn wiring method research...

"In the early 1930s when farms were being wired in great numbers, the only type of nonmetalic cable then made(now known as Type NM)was generally used in the wiring of farm buildings including barns.

It gradually became clear that the usual high humidity and corrosive conditions in barns caused quick rotting of the cable. The outer fabric jacket and the fillers in the cable acted as wicks, drawing moisture into the inside of the cable. With this deterioration came the danger of shortcircuits or shocks and fires.

It became necessary to rewire many farm buildings after only a few years because of the short life of the cable.

This led to the development of what was first called "barn cable",and which has now been standardized as Type NMC nonmetalic-sheathed cable. Later, underground feeder cable Type UF was developed.This too is suitable for wherever Type NMC(or Type NM) is otherwise used."

Seems that Type NMC nonmetalic cable was developed for barns and when UF was invented, it became the cable of choice leading to manufacturers of cable dropping it from production...

shortcircuit
Posted By: kale Re: What is NMC? - 06/23/05 06:05 PM
reno:
The NM info comes from a little booklet I have from Essex Wire. The closest online resource I have found is at: http://www.essexep.com/electrical/techinfo/glossary.htm#n

The NEMA (National Electrical Manufacturers Assoc.) info is used without permission from the www.nema.org website. Search for RV 2-2005.



[This message has been edited by kale (edited 06-23-2005).]
Posted By: Joe Tedesco Re: What is NMC? - 06/23/05 07:20 PM
See 334.2 Definition: 2005 NEC

Type NMC. Insulated conductors enclosed within an overall, corrosion resistant, nonmetallic jacket.


When someone finds this please post a picture or a link.
Posted By: gfretwell Re: What is NMC? - 06/24/05 12:38 AM
My bet still is that it is garden variety plastic NM with a plastic wrapper like MC instead of the kraft paper.
Posted By: DougW Re: What is NMC? - 06/25/05 04:14 PM
gfretwell, you're pretty close.

I had some in the basement from Dad's supplies.

It was virtually identical to the construction of UF, but it was a little more flexible, and had the uniform tan MN color we've come to know and love.

ETA: I remember finding lead jacketed wire serving my old outside porch light that dated back to the 1930's...

<minor hijack> anybody think the industry will standardize on the jacket color codes that are being sold by various makers?

IIRC, orange = 12 AWG, Yellow = 14 AWG ? <hijack>

[This message has been edited by DougW (edited 06-25-2005).]
Posted By: gfretwell Re: What is NMC? - 06/25/05 04:50 PM
orange 10
yellow 12
white 14
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