26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. The correct connection method of Distribution box grounding wire mainly includes the following steps: 1. Grounding of the units: Attach a ground wire from one of. Which means you run a ground wire, typically 4 AWG copper, to the ground bar in the main panel. While traditionally this has been connected to 2 ground rods, in a new building it is recommended, and often required, that it be connected to an Ufer ground, which is basically a ground rod in the. A ground wire is a safety feature that serves as a pathway for electric current to return safely to the ground in the event of a fault. This mechanism helps to prevent electric shocks, equipment damage, and fire hazards.