NEC interpretation issue
NEC interpretation issue
(OP)
I want to know if my interpretation of 110.14(C) is correct.
Can I use the 75°C column ampacities for all gauges? (given the fact that I use 75°C or 90°C insulation and my terminals allow for 75°C wires)
I'm 99% certain that I can, but I want to make sure.
I've seen a lot of devices that allow the use of 75°C wires (especially breakers), and this would prove very useful for feeders.
Thanks in advance.
Can I use the 75°C column ampacities for all gauges? (given the fact that I use 75°C or 90°C insulation and my terminals allow for 75°C wires)
I'm 99% certain that I can, but I want to make sure.
I've seen a lot of devices that allow the use of 75°C wires (especially breakers), and this would prove very useful for feeders.
Thanks in advance.






RE: NEC interpretation issue
Based on NEC 2011 110.14(C) and table 310.15(B)(16).
That's my opinion! Your AHJ's opinion (as well as your local code) may vary.
Good on ya,
Goober Dave
RE: NEC interpretation issue
You also have to be aware of the terminations at the other end of the feeder - and any terminations in between.
Also, the circuit breaker rating is based on use of a certain range of wire sizes being used - this is part of the UL rating. So this (minimum requirement must be met regardless of the NEC.
We use 60 deg C rating for all feeders on 100 A circuits and smaller, regardless. Saves a lot of worry.
David Castor
www.cvoes.com
RE: NEC interpretation issue
aeffects: dpc is much more fluent in this area than I am, your question has many more facets than it seems on the surface.
I would also vote for sticking with 60°C wire for under-100A circuits. Lots less iffy.
Good on y'all,
Goober Dave
RE: NEC interpretation issue
RE: NEC interpretation issue
Rafiq Bulsara
http://www.srengineersct.com
RE: NEC interpretation issue
What kind of risk would you be concerned with?
RE: NEC interpretation issue
Rafiq Bulsara
http://www.srengineersct.com
RE: NEC interpretation issue
RE: NEC interpretation issue
My recommended approach is conservative, I'll agree with that.
David Castor
www.cvoes.com
RE: NEC interpretation issue
RE: NEC interpretation issue
Thank you all for your answers :).
RE: NEC interpretation issue
1. If the device rating is under 100 Amps, and the temperature rating is NOT marked, you have to select Ampacity based on 60 degrees C.
2. Most equipment, even if under 100 Amps, is listed for 75 degrees C, so you use the 75 degree C column in the Article 310 Tables.
3. The Ampacity of NM sheathed cable, also known as "Romex", is always based on 60 degrees C.
--> I'm writing this from memory alone, and not citing NEC sections. Somebody please jump on me if I'm wrong.
RE: NEC interpretation issue