NMB

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Re: NMB

Sam, you sure are up late aren't you?

Roger
 
Re: NMB

Oh man, Bob didn't notice yet.

Yeah, The work I have right now is unimportant enough that I can stick in the corner and ignore it until I decide I have a whole weeks worth.

It's slow this time of year for me. Built in vacation. ;)
 
Re: NMB

Yes.

334.112 is part of the Construction Specifications of the cable.

It requires the cable be produced with 90 C insulated conductors.

334.80 is in the Installation section of the NM article.

334.80 requires us to treat NM as 60 C but permits us to use the 90 C rating for derating purposes as long as after derating we come in under the 60 C rating.
 
Re: NMB

Ok, fair enough.

Except I got caught in this derating term too, you mean correction factor?
 
Re: NMB

Originally posted by physis:
Ok, fair enough.

Except I got caught in this derating term too, you mean correction factor?
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Yes, no, maybe :D you can find the word derating a number of times in the code.

As an example look half way into 334.80 and you will see 'derating'.

I take derating as a way to describe the use of Table 310.15(B)(2)(a) Adjustment Factors and / or Table 310.16 Correction Factors.
 
Re: NMB

You didn't want to pick on me.

(This comment really requires the Jerry Sienfeld voice of disapproval). Are you familiar with it?
 
Re: NMB

Well, I got called on it. So I should just have you explain it for me. You're the best Bob, anyway, here's the guys e-mai%$#%* &*^ $##$*.

:D
 
Re: NMB

i wrote it earlier and i will write it again the -b means the non metallic sheathed cable comes with a bare or insulated ground. nm is a flat 2 conductor cable. nm-b is a 3 conductor cable
 
Re: NMB

Originally posted by crankshaft:
the -b means the non metallic sheathed cable comes with a bare or insulated ground. nm is a flat 2 conductor cable. nm-b is a 3 conductor cable
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Crankshaft I am sure that is what someone told you. However please follow this link that Roger posted.

Southwire

Southwire makes NM, I am sure they know what the B means.

Here is what Southwire (A manufacturer of NM) has to say.

The "B" denotes that individual conductor insulation is rated 90?C; however, ampacity is limited to that for a 60?C conductor (see NEC Section 336-26, 1999 edition). Thermoplastic (PVC) conductor insulation-nylon jacketed, with overall PVC cable jacket.
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The B has nothing to do with bare, insulated, round, flat or number of conductors.
 
Re: NMB

Ambient air is the normal high temp for the area. I usually assume that outdoors (here in the South) to be 40 degrees C and indoor to be 30 degrees C (we like our air conditioning)
When Romex first came out it was labeled NM and had 60 degree insulation, then came NM-A with 75 degree insulation then NM-B with 90 degree insulation. You still need to use the 60 degree column for ampacity though.
 
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