26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. 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. Whether you're a seasoned pro or just starting out, this comprehensive guide will give you practical. 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 DESIGN THEORY. Protective grounds must be installed so all phases of lines or cable are visibly and effectively bonded together in a multi-phase. The IEC (International Electrotechnical Commission) and BS 7671 (British Standard for Electrical Installations) both provide essential requirements for electrical installations, including those for fuse boards like garage unit, consumer unit and distribution board. While the IEC 60364 standard.