Around here PNB is quite common. Several years ago at the early stages of concerns about PME and EV chargepoints, I questioned the need for PME mitigation measures on PNB systems. I was told by a NIE engineer that it was mandatory for the customer to treat PNB exactly as per the requirements for PME.
Anyway, for most troops, I don't think too much effort will go into a definite determination, much like the assessment of maximum demand or the rating of the protective device acting at the origin!
Nice to see a clearly labelled earthing arrangement there. Also a clear visual indication that the after diversity maximum demand is slightly higher than the rating of that main switch in the wylex board !
Actually, I took the photo because there was burning at the line at the top of the Wylex board. I was going to use it in class as an example of why piggybacking can be less than a good idea, but it also leads nicely into the A4 changes.
