RICK BOYD

When I buy NM I can only find NM-B
but can't find it listed in the book .
I don't see it in 310-16, so what's it's ampacity? I know, but I want it in print
one supplier said it was NM with 90'F conductors but I can't find it in writing.
I like to read it cuz
I don't believe anything I am told and only half of what I see.

Rick

ps: when I tell the salesman I want 12-2 nm
he always says "do you want that with ground"
and I say NO and he says "we don't have it without ground"
and I say "DUH"

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I know you understand
what you thought I said
but what you heard
is not what I meant

BEAMEUP

look in 334

Bob Badger

Article 334 covers all types of NM, in regards to temperature rating look at 334.80.

You can use 90 C as a starting point for derating but in no case may you exceed the 60 C rating.

RICK BOYD

Ok ,but what I find at the store is NM-B whether it is southwire or romex brand and that is not in the book, but I do see 334.8 and they referance NM , NMC and NMS but not NM-B

QUOTE=Bob Badger;137162]Article 334 covers all types of NM, in regards to temperature rating look at 334.80.

You can use 90 C as a starting point for derating but in no case may you exceed the 60 C rating.[/quote]

__________________
I know you understand
what you thought I said
but what you heard
is not what I meant

Chris Kennedy

Its in the book.

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Bulldozers and Dirt

River Boy

Years ago there was just NM or, non-metallic 60 C romex. Then sometime in the early 80s the NEC decided that NM needed to have a higher insulation rating for attics so they started putting 90 C THHN in the romex sheath and called it NM-B, as opposed to the old stuff which they temporarily named NM-A to differentiate between the two. They left a window of time for all the old stock, (NM-A) to be used up. When an inspector looks at a romex sheath and sees NM-B he knows he is looking at 90 C wire.

Briancraig81

I'm not trying to HiJack but can someone tell me what your supposed to do when your hanging a new fixture that say's use only 90 C conductors and what your connecting it is 60?

I asked my old boss this a few years back and he told me that they changed the temp rating back in the 80's (Which is what you guys are saying) and for me to just hang the fixture and not worry about it. He did tell me to always leave the fiberglass insulation on a fixture because it helps with the temp rating.

Can someone set me straight on this?, Thanks.

Dennis Alwon

Most people don't worry about it but you can take a piece of #10 THHN insulation and sleeve it over the old 60C insulation. We do this alot when the old knob and tube is cracked beyond repair.

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4 Out Of 3 People Have Trouble With Fractions

Bob Badger

Code wise you can not hang the fixture,


I think most people do.

NolaTigaBait

I've done this as well. I'm surprised Dennis would do this.

Dennis Alwon

Wow- I didn't realize I set the standard so high.

I look at it this way- what's a better install. If I can replace the wire I will but if we are between floors etc I find my solution to be the better of the two evils. The existing old fixture is probably a bigger hazard than the new fixture would create. So---- the lesser of the 2 evils is a good solution esp. with the higher temp. insulation.

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4 Out Of 3 People Have Trouble With Fractions

InPhase277

Using some of the fiberglass high temp sleeves used in electric heaters and ranges over the old wires may be a good solution.