310.15(B)(3)(c) and XHHW-2
- Thread starter augie47
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I don't know Gus but it is new in the 2014
kwired
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- NE Nebraska
editorial comment in my E-book version of 2014 after that exception says:
Change from 2011 NEC:
New exception that exempts conductors with thermoset insulation rated at 90°C or higher from this ampacity adjustment.
Do not know why though. You would think that there would still be an ampacity level, just that maybe XHHW-2 is actually good for more then 90 C and they are not willing to admit it yet. As is written there is no temp limit - but only for roof top applications:?
Change from 2011 NEC:
New exception that exempts conductors with thermoset insulation rated at 90°C or higher from this ampacity adjustment.
Do not know why though. You would think that there would still be an ampacity level, just that maybe XHHW-2 is actually good for more then 90 C and they are not willing to admit it yet. As is written there is no temp limit - but only for roof top applications:?
Thanks, Dennis. I was working on materials for my classes and reviewing Mikes video as a guide.
I didn't see it on my 2014 but, since TN is not on 201, the only copy I have is from the ROP report.
Mike's video must have been based on the 2014.
Quite possibly. Don't know about the willingness part, though. The table only goes to 90°C. You have to remember there are listed higher temperature wires that are not recognized by the NEC.
kwired
Electron manager
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- NE Nebraska
But yet for other applications we are supposed to treat it as 90C whether it actually is or not. Other conductors that are rated over 90C are marked accordingly. I do agree 310.15(16) only goes to 90C, but some other tables do go higher so it is not like over 90C is unheard of.
The other Tables only have different conditions of use, not different temperatures. Look at Table 310.104(A). XHHW-2 is limited to a 90°C maximum operating temperature... so if XHHW-2 can withstand a higher temperature, Code has to use imaginative ways to permit it. :happyyes:
kwired
Electron manager
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- NE Nebraska
I guess it is sort of like using 150C conductor but you still need a minimum conductor based on 60 or 75 rating of the supply termination in almost all cases, but it can withstand a 150C ambient on it's way to the load supplied.
The thing that is usually unique in that situation as well as a RTU application is there is usually only one circuit so you don't need to make adjustments because of other circuits in same raceway or cable, it is just ambient temp that is a potential limiting factor.
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