romex rated 90 degrees?

[Cleveland Apprentice]

I've always thought NM cable was rated at 60 degrees, but heard some are manufactured at 90 degree rating. I'm not sure if this is true and thinking Colonial is one of the manufacturers. Anyone else heard of this?

Also, when derating romex in general, why do we derate at the 90 degree column if the cable is rated at 60 degree? Thanks.

 

[raider1]

The conductors within the NM cable are required to be rated at 90 Degrees C so we can use the 90 degree column of 310.16 for ampacity adjustments provided that the final ampacity does not exceed what is listed in the 60 degree column.

Chris

 

[Cleveland Apprentice]

So all conductors are required to be rated at 90 deg column as long as you don't exceed ampacity of 60 or 75 deg? 90 deg column I take it as strictly for derating purposes only?

 

[raider1]

So all conductors are required to be rated at 90 deg column as long as you don't exceed ampacity of 60 or 75 deg?

Not necessarily, for example THWN is only rated at 75 degrees C when used in a wet location. THWN-2 is rated for 90 degrees for either wet or dry locations.

90 deg column I take it as strictly for derating purposes only?

You are correct.

Chris

 

[Cleveland Apprentice]

Thanks, got better understanding now.

 

[squaredan]

hey Cleveland I have posted this link before and I think it will help you understand better about T310.16 and all.. Check out his site it might be worth purchasing this DVD, not trying to push his stuff but it did help for me...

http://www.youtube.com/user/MikeHoltNEC#p/u/12/WL81zOzNagM

also look at 334.80

Dan

 

[Cleveland Apprentice]

Thanks squaredan!