When considering service entrance conductors of 4/0 AWG, what is the smallest main bonding jumper permissible?

For the scenario described involving service entrance conductors of 4/0 AWG, the minimum size for the main bonding jumper can be determined by referencing the National Electrical Code (NEC) guidelines. According to NEC Table 250.102(C)(1), the size of the main bonding jumper must be based on the size of the service-entrance conductors.

For conductors sized at 4/0 AWG, the NEC requires that the minimum size for the main bonding jumper is 2 AWG copper or 1 AWG aluminum. The choice marked as “B” corresponds to 2 AWG copper, which aligns with the NEC requirements for establishing proper grounding and bonding practices within electrical systems.

The function of the main bonding jumper is critical in ensuring that all conductive parts of the service equipment are properly connected to the grounding system. This connection helps to facilitate the safe operation of electrical systems, allowing fault currents to return to the ground safely and effectively, thereby minimizing the risk of electrical hazards.

Hence, the answer reflecting 2 AWG as the minimum size for the main bonding jumper is indeed the correct one, adhering to the electrical standards that promote safety and functionality in electrical installations.