Low Temperature Adjustment

[Dennis Alwon]

If the ambient temperature is 59° with #3 copper 90C wiring then can I actually load my conductor to 112 amps and use a 125 amp breaker.

#3 at 75C is 100-- 100 * 1.12 (temp correction) = 112 amps or do I have to use the correction at the 90 C and never be over the 75C at 100 amps.

 

[david luchini]

If the ambient temperature is 59° with #3 copper 90C wiring then can I actually load my conductor to 112 amps and use a 125 amp breaker.

#3 at 75C is 100-- 100 * 1.12 (temp correction) = 112 amps or do I have to use the correction at the 90 C and never be over the 75C at 100 amps.

You can load the #3 to 115 amps and use a 125A breaker (assuming your not using any continuous loads which may require a larger conductor.)

 

[Dennis Alwon]

You can load the #3 to 115 amps and use a 125A breaker (assuming your not using any continuous loads which may require a larger conductor.)

That is what I thought but I think you mean 112 amp load. No?

 

[david luchini]

That is what I thought but I think you mean 112 amp load. No?

The 75deg correction factor for 59deg F ambient is 1.15.

You could apply the 90deg correction factor to the 90deg ampacity 115A x 1.12= 129A, but I don't believe that 110.14(C)(1)(b)(2) will allow the conductor to be used beyond the 75deg ampacity, which is 115 amps at 59deg F.

 

[tortuga]

The 75deg correction factor for 59deg F ambient is 1.15.

You could apply the 90deg correction factor to the 90deg ampacity 115A x 1.12= 129A, but I don't believe that 110.14(C)(1)(b)(2) will allow the conductor to be used beyond the 75deg ampacity, which is 115 amps at 59deg F.

I am getting Déjà vu.