NMB

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Re: NMB

I will not mince words, what I will say and be clear about it....... is that derating in residential does not exist , at least in common practice of what little I have seen .

Is it different where you reside?????
 
Re: NMB

The question is:

Using Table 310.16, assuming an ambient temerature of 114?-122? F in an insulated attic, it seems that hot to me, should we be using a correction factor of

.58 X 25 per the 60? C column for 14.5 amps for 12 AWG NMB

or

.82 X 30 per the 90? C column for 24.6 amps for 12 AWG NMB (of course the *)

Or is there somewhere else you might find NM of type B, C, or S aside from the cable table? (cable table :D )
 
Re: NMB

ARTICLE 334 Nonmetallic-Sheathed Cable: Types NM, NMC, and NMS

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.
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Re: NMB

I don't mean to be difficult with you Bob, (I suppose you already know what that means) but I'm not buying it.

Rush Limbaugh says "words mean stuff", I say "letters mean stuff". :)

[ January 14, 2005, 04:47 AM: Message edited by: physis ]
 
Re: NMB

That's wierd, It took me about 30 seconds to post that and my machine is showing 3 minutes between us.
 
Re: NMB

Originally posted by physis:
Rush Limbaugh says "words mean stuff", I say "letters mean stuff". :D

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Your right, the 'B' does mean something, it means it is NM cable modified with 90 C conductors. :cool:

Plain NM had 60 C conductors.
 
Re: NMB

Yes the - makes all the difference. :p

How about this?

334.112 Insulation.
The insulated power conductors shall be one of the types listed in Table 310.13 that is suitable for branch circuit wiring or one that is identified for use in these cables. Conductor insulation shall be rated at 90?C (194?F).

FPN:Types NM, NMC, and NMS cable identified by the markings NM-B, NMC-B, and NMS-B meet this requirement.
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Read the fine print note.

Notice NM-B, NMC-B and NMS-B.
 
Re: NMB

Without my starting off on that now, I'll just ask you.

Does that say NM must be -B?

Edit: stupid extra letter had to be removed.

[ January 14, 2005, 05:00 AM: Message edited by: physis ]
 
Re: NMB

Originally posted by physis:
Does that say NM must be -B?
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Well no, as you do not see the -B in the code section only in the FPN.

The code section states the conductors must have 90 C insulation.

As a favor the FPN tells us a cable with -B will have those 90 C conductors.

So if you can find a cable without the -B and has 90 C condutors (and you can prove that) you would be all set. :D
 
Re: NMB

Alright wise guy, does it say NM must be 90? C?

And then say we must treaet it as 60? C?

:D
 
Re: NMB

Originally posted by physis:
Alright wise guy, does it say NM must be 90? C?

And then say we must treaet it as 60? C?

:D
Click to expand...
Sure, now we are right back to 334.80 which I posted a little while ago.
 
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