Host of ElectricianLIVE.com
- McKinney, Texas
- Master Electrician & Director of Codes and Standards
That would be awesome!
I guess I am wondering what is holding NM back to 60*C when it could in theory handle 75*C. Type AC cable can run at 75*C when not in thermal insulation, and my understanding MC is regardless.
Well that I am not old enough to answer my friend...lol...I know that the 60C has been in the NEC a long time and while we do have studies to show the affects of Type NM Cable installed in thermal insulation to warrant an adjustment I would guess the roots of the 60C stem from UL 719 and the STP's that worked on that during it's development.
If time permits I am sure I can research the answer to that question. However as it stands now the main limiting factor is the UL 719 which of course led to the language in 334.80.
I do believe their are some proposals coming up (UL not NEC) to mandate a temperature rating on the sheathing of Type NM..but I can tell you based on the material it will be equivalent to or exceed that of the 60C...just based on the 30mils thickness and compounds...but i will look into it for you my friend and post what I determine.