What is the minimum size required for a grounding electrode conductor in an ungrounded DC system?

The minimum size required for a grounding electrode conductor in an ungrounded DC system is specified in Section 250.166 of the National Electrical Code (NEC). This section outlines the sizing requirements for grounding conductors based on the size of the service-entrance conductors. Understanding this section is critical because it provides guidelines that ensure safety and protection of electrical systems by minimizing the risk of overcurrent and ensuring proper grounding.

Section 250.166 specifically details how the size of the grounding electrode conductor is determined based on the maximum size of the ungrounded conductors. This ensures that the grounding system can handle potential fault currents effectively, which is particularly important in preventing damage and maintaining safety in ungrounded systems.

Although local codes (as mentioned in the first choice) may also set standards, Section 250.166 serves as a foundational reference within the NEC that is adopted in many jurisdictions, making it the correct choice for determining the grounding electrode conductor size in this context.