The minimum size of each of the copper conductors connected between the ground bar and each service pipe is ___ AWG.

The minimum size of each of the copper conductors connected between the ground bar and each service pipe is 2 AWG. This specification aligns with the National Electrical Code (NEC) requirements which outline the size of grounding conductors to ensure adequate safety and performance in electrical systems.

Using a 2 AWG copper conductor provides sufficient capacity to carry fault current effectively, thereby maintaining safety in the event of a fault. The conductor's size is important as it directly affects its ability to handle potential overcurrents without overheating and ensures that it can effectively connect the grounding system to the service equipment, thereby reducing the risk of electrical shock or fire.

Larger sizes, like 4 AWG, 2/0, and 3/0, exceed the minimum requirement for most typical residential or commercial installations where 2 AWG is sufficient to meet the safety thresholds established in the NEC. In other scenarios, such as for grounding of larger installations or specific environmental conditions, larger conductors may be required, but as a standard minimum for the specified application, 2 AWG is correct.