Jpflex
Electrician big leagues
- Location
- Victorville
- Occupation
- Electrician commercial and residential
There seems to be a conflict of rules for conductors terminating on devices. 110.14 C 1 states:
“The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor or devic.”
Therefore, if my single phase 100 ampere panel has a main breaker listing a terminating temperature only at 75 degrees celcius, I would use #3 THHW wire rated with 90 degree Celsius insulation with 115 amperes present.
Then based on my location using the chart for ambient temperature in my location at 100 degrees and 90 degree Celsius rated insulation, I would use NEC chart 310.15 B1 to find my detracting factor of 0.91% which would mean this wire’s maximum ampere rating would be 0.91 x 115 = 104 amperes
Then checking the 75 degree column on NEC chart 310.16 the #3 AWG wire is good for exactly 100 amperes, so I would use this as minimum size wire. (Building load calculation omitted as owner boss selected this load center)
Additionally, 215.2 says to size feeders to the larger of:
1) 125 percent of continuous loads plus 100 percent of non continuous loads or
2) not less than the maximum load to be served after adjustment factors (which is the option we are using)
However, NEC 110.14 C 1 (a) also says:
“14 through 1 AWG shall be used only for conductors rated at 60 degrees Celsius
This would normally contradict the first statement but 3) states conductors with higher temperature rating may be used if the the equipment is listed and identified for use with such conductors
So can I stick with a smaller #3 AWG THHW at 75 degrees wire good for exactly 100 amperes (not considering voltage drop) or
Should I use a # 1 AWG THHW sized for the 60 degree ampacity for 110 amperes
“The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor or devic.”
Therefore, if my single phase 100 ampere panel has a main breaker listing a terminating temperature only at 75 degrees celcius, I would use #3 THHW wire rated with 90 degree Celsius insulation with 115 amperes present.
Then based on my location using the chart for ambient temperature in my location at 100 degrees and 90 degree Celsius rated insulation, I would use NEC chart 310.15 B1 to find my detracting factor of 0.91% which would mean this wire’s maximum ampere rating would be 0.91 x 115 = 104 amperes
Then checking the 75 degree column on NEC chart 310.16 the #3 AWG wire is good for exactly 100 amperes, so I would use this as minimum size wire. (Building load calculation omitted as owner boss selected this load center)
Additionally, 215.2 says to size feeders to the larger of:
1) 125 percent of continuous loads plus 100 percent of non continuous loads or
2) not less than the maximum load to be served after adjustment factors (which is the option we are using)
However, NEC 110.14 C 1 (a) also says:
“14 through 1 AWG shall be used only for conductors rated at 60 degrees Celsius
This would normally contradict the first statement but 3) states conductors with higher temperature rating may be used if the the equipment is listed and identified for use with such conductors
So can I stick with a smaller #3 AWG THHW at 75 degrees wire good for exactly 100 amperes (not considering voltage drop) or
Should I use a # 1 AWG THHW sized for the 60 degree ampacity for 110 amperes
