Attach a ground wire from one of the threaded studs (A) at the bottom of the housing, to the mounting plate (B). The ground resistance between all system parts shall be <. Power from factory ground must be installed by a qualified electrician. 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. The voltage, system arrangement, loads connected, and continuity of.