Looking for a little clarity on using type 2 SPD protection in a sub main distribution board and the need to export a 16mm2 earthing conductor from the main earthing terminal. the idea fits regulations 534.4.8 and 534.4.10, but for me the idea does not spring from the regs. Looking at GN1, pages 61 to 65 and at table 3.13 doesn't seem to give me much clarity. I'm missing something obvious. It leads me to think that a relatively small supply to an adjacent garage or garden workshop may require SPD protection at the destination and consideration given to running 16mm2 CPC.
Any clarity gratefully received or just point out the obvious.
