The metal box of the distribution box, the electrical installation board, and the metal base and casing of the electrical appliances in the box must be grounded. The protective neutral wire should be reliably connected through the terminal board. Avoid installing in a humid and corrosive environment to prevent equipment damage. Unless installed in a complete metallic raceway, each branch circuit shall contain a. 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. In factories, construction sites, and even commercial buildings, this question pops up all the time.