The minimum size of an equipment grounding conductor for a circuit protected by an automatic overcurrent device rated at 200 amperes should be which size?

The correct answer is based on the requirements set forth in the National Electrical Code (NEC) for sizing equipment grounding conductors. For a circuit protected by an automatic overcurrent device rated at 200 amperes, the NEC provides a specific formula to determine the minimum size of the grounding conductor required to ensure safety and proper functioning of electrical systems.

According to NEC Table 250.122, the minimum size of an equipment grounding conductor increases with the rating of the overcurrent device. For a 200 ampere service, the code specifies that the minimum size for the equipment grounding conductor should be 6 AWG copper. This size ensures adequate conductivity for fault current, helping to prevent potential hazards such as overheating and providing an effective path for ground fault currents to facilitate the operation of protective devices.

The other options, which suggest smaller conductor sizes, do not meet the safety requirements outlined in the code for a 200 amp circuit, thereby failing to provide the necessary protection.