ampacity of the conductor

[Johndo12345]

Hi Mike.
According to 310.15, the ampacity of a conductor is calculated to carry
current CONTINUOUSLY without getting damage, so why do I have to multiply
125% to the ampacity of the continuous load when I size the wire for my
branch circuit.

Thank you.

 

[charlie b]

Good question. :happyyes: Wish I had a good answer. :happysad: Best I can offer is that it might be because the terminations are not able to handle the same current continuously without overheating.

Welcome to the forum.

 

[mbrooke]

Circuit breaker crowded together in a panel board trap heat which can lower their trip curve.

 

[infinity]

Circuit breaker crowded together in a panel board trap heat which can lower their trip curve.

Yup, that's why equipment that is designed to operate at 100% continuous is listed for continuous operation. {210.19(A)(1)Exception}

 

[kwired]

Yup, that's why equipment that is designed to operate at 100% continuous is listed for continuous operation. {210.19(A)(1)Exception}

+1