What size grounding electrode conductor is generally required for #4 copper service lines?

The appropriate size for a grounding electrode conductor related to a #4 copper service line is governed by the National Electrical Code (NEC), which provides specific guidelines for grounding and bonding to ensure safety. For a #4 AWG (American Wire Gauge) copper service conductor, the NEC specifies that the grounding electrode conductor should typically be a #8 AWG copper wire.

This sizing is based on the need for the grounding system to adequately handle potential fault currents, providing a safe path for these currents to dissipate into the ground. The #8 copper conductor meets the necessary requirements for a service line of #4 size, ensuring efficiency in the grounding system without excessive resistance.

The other choices are either too large or too small compared to the requirements set forth by the NEC, making #8 copper the right choice for providing effective grounding in residential electrical installations.