Each DISTRIBUTION BOX and controller must be grounded. 26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. Grounding of the units: Attach a ground wire from one of. Today, we're diving deep into the world of distribution box grounding, breaking down the standards, and shining a light on those sneaky mistakes that even experienced electricians sometimes make. This helps to reduce the potential difference that exists between conductive parts and the earth. The fixing method should be firm and reliable to avoid movement or tilting of the box due to vibration or collision. Preparation: First, you need to prepare some necessary tools, including grounding wire, grounding rod, voltmeter, insulating gloves and insulating tools.