DNO allowance for tails protection from their fuse is commonly 3M. - 3M is deemed AFAICT to extent through any in-line isolator, whether or not that isolator is property of DNO or is consumer fitted part. (The latter is not spelled out by DNO SSEPD who just state the 3M tails figure without further qualification).
If said isolator begins to sprout additional complexity such as MCB and SPD as a shunt addition, my interpretation (Definitions, part 2) is that it still doesn’t yet qualify as a consumer unit, hence the 3M rule could be said to still run straight through it as far as the farthest CU.
- Any thoughts?
