26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. In outdoor or industrial electrical environments, the metal casing of the ip65 stainless steel enclosure must form a complete conductive circuit. Each DISTRIBUTION BOX and controller must be grounded. 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. The equipotential bonding of its metal casing is the underlying logic that ensures the reliable operation of the system. Think of it this way: That distribution box in your facility? It's not just a metal container – it's the. As for your title question: yes, it's sufficient to ground an outlet only to its box -- if, and only if, the box itself is properly grounded. To add to Greg's answer, it's important to note when and where you can ground to the box.