Q. What is the minimum size requirement for branch circuit overcurrent protection?
Find the Answer
A. Branch-circuit overcurrent devices must have a rating of not less than 125% of the continuous loads, plus 100% of the noncontinuous loads [210.20(A)]. Note: See Sec. 210.19(A)(1) for branch-circuit conductor sizing requirements.
Exception: If the assembly and the overcurrent devices are both listed for operation at 100% of their rating, the branch-circuit overcurrent device can be sized at 100% of the continuous load.
It’s important to note that equipment suitable for 100% continuous loading is rarely available in ratings under 400A.
As noted in Sec. 210.20(B), branch-circuit conductors must be protected against overcurrent in accordance with 240.4. In addition, as noted in Sec. 210.20(C), branch-circuit equipment must be protected in accordance with 240.3.