Grounding of the units: 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. Understanding how to ground metal electrical box components is not just about following code—it's about protecting your home and family. This guide provides clear, step-by-step instructions for beginners. 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. This pathway diverts fault. In this comprehensive guide, we're going to demystify the process of how to ground a metal box. These locations are usually marked with grounding symbols for easy cable crimping.