Attach a ground wire from one of the threaded studs (A) at the bottom of the housing, to the mounting plate (B). The bare wire is connected to one or more long metal bars driven into the ground, or to a wire buried in the foundation, or sometimes to the water supply pipe. Good equipment grounding ensures personnel safety. Most North American distribution systems have a neutral that acts as a return conductor and as an equipment. Four wires are involved in supplying the main panel with power. This practice is essential. On the US market, a 5.