Type NM cable temp. rating

[electricman2]

What is the temperature rating of the conductors in type NM cable? Seems like I heard somewhere that it is 90C. I have a fixture that requires 90C conductors and I need to know if I can run NM cable to it.

 

[pierre]

Re: Type NM cable temp. rating

If the NM cable you are using is new, not from stock that has been sitting on a shelf , The conductors are rated for 90C and you can use it for the fixtures. 334.80

Pierre

 

[tonyi]

Re: Type NM cable temp. rating

Originally posted by electricman2:
What is the temperature rating of the conductors in type NM cable? Seems like I heard somewhere that it is 90C. I have a fixture that requires 90C conductors and I need to know if I can run NM cable to it.

Older "NM", [thicker sheath, thick conductor insulation] is 60 degrees insulations.

"NM-B" is 90 degree insulations

The "B" is what indicates 90 degree insulations vs 60.

 

[Guest]

Re: Type NM cable temp. rating

That might lead us to infer that there is:

NM=60
NM-A=75
NM-B=90
NM-C=wet
NM-S=hybrid

 

[electricman2]

Re: Type NM cable temp. rating

Thanks for all the responses.

 

[tom baker]

Re: Type NM cable temp. rating

While the rating of the conductors is 90 C the overall ampacity is based on the cable jacket or 60 deg C, see section 334.84

 

[Guest]

Re: Type NM cable temp. rating

Good catch!

 

[iwire]

Re: Type NM cable temp. rating

It is 90C as far as using it near ballasts and in fixture box's.

It is 90C when you have to do ampacity adjustments.

But when done with any ampacity adjustments as Tom has said you still can not use it above the 60C rating.

All new NM has 90C conductors, article 334 only addresses NM, NMC and NMS.

[ October 14, 2003, 04:37 AM: Message edited by: iwire ]