For a 3-phase, 120/208-volt, 4-wire system with service entrance copper conductors of 750 kcmil, what is the minimum size of the copper grounding electrode conductor to a metal water pipe?

In a 3-phase, 120/208-volt, 4-wire system, the minimum size of the copper grounding electrode conductor is determined by the size of the service entrance conductors and the type of grounding system in use. The National Electrical Code (NEC) provides guidelines for these calculations.

For service entrance conductors of 750 kcmil, you would look to NEC requirements, particularly in Table 250.66, which outlines the necessary grounding electrode conductor size based on the size of the largest ungrounded service conductor.

According to the NEC, when the service entrance conductors for a system are 750 kcmil, the copper grounding electrode conductor to a metal water pipe should be sized accordingly. For copper conductors, the minimum size grounding electrode conductor required is typically 2 AWG when related to larger service sizes.

This sizing ensures that in the event of a fault condition, the grounding system can effectively carry fault currents and help protect both the equipment and personnel from electrical shock or damage. Proper grounding is crucial for the safety and efficacy of the electrical system, and thus, following the established code and requirements is important in electrical installations.