If a service line is #4 copper or smaller, what should be the size of the grounding electrode conductor?

The correct grounding electrode conductor size for a service line that is #4 copper or smaller is #8 copper. This is based on the applicable electrical codes that dictate the sizing of grounding electrode conductors in relation to the service entrance conductors.

When determining the appropriate size for the grounding electrode conductor, the goal is to ensure adequate safety and performance in the event of an overcurrent or fault condition. For copper conductors, a #6 copper conductor would be required for service lines larger than #4, thus establishing a pathway for fault current that is effective and compliant with code requirements.

In contrast, using a grounding electrode conductor that is #4 copper, #10 copper, or smaller would not meet the necessary requirements for grounding performance; they are not adequately sized for a #4 copper service line. This reinforces the need for proper sizing to guarantee the safety and functionality of the grounding system in residential installations.