26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. Each DISTRIBUTION BOX and controller must be grounded. 148 (Grounding Conductor): Requires metallic junction boxes—and by extension, cabinet doors—to bond to ground using a designated grounding screw or clip. 28 (Box Materials): Metal boxes (like your cabinet) must be reliably grounded and. of all overhead line distribution equipment is always grounded and bonded to cont all be consider as a priority, if not available, then 70 mm2 copper conducto r normal soil condit soil without much difficulty. The grounding system provides a low-impedance path for fault current and limits the voltage rise on the normally non-current-carrying metallic components of the electrical distribution system. Attach ground bus to the wall, at 30 inches above the floor, with standoff insulators.