26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. Here are the steps on how to ground a power distribution box: 1. Make sure all tools are intact to prevent accidents during the grounding. The transition from PVC conduit to a metal electrical box is a common requirement in residential and light commercial wiring projects. Rigid PVC conduit is non-metallic and corrosion-resistant, frequently used to route electrical conductors, but it must terminate into a sturdy metal enclosure that. However, with plastic distribution boxes, the grounding process can be somewhat complicated. Each DISTRIBUTION BOX and controller must be grounded.