What is the minimum size grounding electrode conductor required for a 400-ampere feeder supplying a panelboard with a largest ungrounded conductor of 600 kcmil aluminum?

To determine the minimum size grounding electrode conductor required for a 400-ampere feeder, it's crucial to refer to the National Electrical Code (NEC). The NEC outlines specific requirements based on the size of the largest ungrounded conductor and the current-carrying capacity of the feeder.

In this case, the largest ungrounded conductor is 600 kcmil aluminum. For a feeder of this size, the NEC tables provide guidelines for required grounding electrode conductor sizes based on the feeder's ampacity.

When assessing the choices, the grounding electrode conductor size for a 600 kcmil aluminum conductor falls in the category where a 1/0 AWG copper conductor meets the necessary requirements for a 400-ampere feeder. The choice of 1/0 AWG copper specifies that it is appropriate to adequately ground the system without compromising safety or performance.

In summary, a 1/0 AWG copper grounding electrode conductor is sufficient, as it aligns with the NEC requirements for the given feeder size and ampacity, ensuring effective grounding for safety.