26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. 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. Grounding of the units: Attach a ground wire from one of. Choose the right box based on environment (indoor/outdoor), load capacity, and durability. Check for proper IP/NEMA ratings and material quality. Ensure safe placement: install in dry, accessible areas with good ventilation and at appropriate height (typically ~1. So how should the distribution box be grounded? 1. The grounding "bus" (grounding bus, PE bus) in the box is directly connected to the power ground wire or grounding system; 2.