Attach a ground wire from one of the threaded studs (A) at the bottom of the housing, to the mounting plate (B). If the distribution box is poorly grounded, it may cause electrical system leakage, short circuit and other faults, and even cause electric shock accidents. 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. Bottom line: That door is part of the enclosure. Skip. There are several factors that make substation grounding absolutely necessary. This helps to reduce the potential difference that exists between. 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. During fault conditions, low impedance results in high fault current flow, causing overcurrent protective. Outdoor low-voltage power distribution boxes (hereinafter referred to as "distribution boxes") are low-voltage distribution equipment used in 380/220V power supply systems to receive and distribute electrical energy.