Is it true that Table 250.66 is only used for sizing grounding electrode conductors for AC services?

Table 250.66 in the National Electrical Code (NEC) is not limited to AC services; it is applicable to both alternating current (AC) and direct current (DC) systems. This table provides essential information for sizing grounding electrode conductors based on the size of the largest ungrounded service-entrance conductor or equivalent.

The purpose of grounding electrode conductors is to ensure that faults are cleared effectively and safely by providing a low-resistance path to ground, which can apply to both residential and commercial installations. Therefore, stating that Table 250.66 is used only for AC services is misleading, as its provisions are relevant across various types of services, including DC configurations when applicable. This broad applicability underscores the importance of grounding methods for various electrical systems, not just limited to AC.