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. For example, for High And Low Voltage Distribution Cabinets, the distribution box needs to be grounded regardless of size. The grounding "bus" (grounding bus, PE bus) in the box is directly connected to the power ground wire or grounding system; 2. 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. Whether you're a seasoned pro or just starting out, this comprehensive guide will give you practical. Here are the steps on how to ground a power distribution box: 1. Usage: Use this extension box with no extra radiation (voltage) as exists on regular extension boxes. Make sure all tools are intact to prevent accidents during the grounding.