26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. If you've ever found yourself scratching your head over whether that metal door on your distribution cabinet really needs a grounding wire, you're not alone. In factories, construction sites, and even commercial buildings, this question pops up all the time. Your boss might insist on it, while your. Grounding and bonding limit overvoltages, stabilize the voltage to the ground during regular functioning, and ease the proper operation of circuit breakers and fuses. Ground wires reduce the risk of injury and damage from faulty equipment. Equipment grounding: everybody's favorite topic.