UK TN-S Looped supply - earth upgrade. Need to isolate neighbour/refer to DNO?

[pc1966]

Probably the original was 4mm (or imperial equivalent) but bare, so upper temperature limit for adiabatic quite high!

Still, in the increasingly PME world there could well be concerns that segments of TN-S earthing carry neutral currents as well for long periods under open PEN conditions so they might want it sized up a bit?

 

[Msitekkie]

I'm also pretty certain the DNO will be happy with the conductor size.
A long-standing quest for me has been finding a reliable set of time/current curves for BS1361 fuses - there was a graph in the 16th edition, but it was much more conservative than every other one I have found online. (If anyone has recommendations I'd love to know!)

Anyway, with 60A fuse, PFC of 657amps, the old 16th edition graph says it trips in 0.6 seconds. Other graphs have as low as 0.2 seconds.
For an 80A fuse most graphs online say about 1 second.

Bung all that in here : CPC Sizing Tool - https://myelectrical.com/tools/cpc-sizing-calculator
If 0.2 seconds, You get 3mm for copper, 3mm for aluminium and 4mm for steel.
If 1 seconds, you get 3mm for copper, 5mm for aluminium, and 8mm for steel.
Good chance it's ok.

For other reasons above I'd still suggest the DNO should have a look at that, in only to confirm that an approved earth is still connected to next door, and that those clamps have not done any damage.

Thanks again Tim and everyone else. UK Power Networks are booked in to go have a look on 18th Feb. Will be interesting to see what they do.
The unsheathed cable disappears under the floor. If it was the DNO earth wouldn't it be a "sweated" connection to the sheath at the top of the cable where the other clamps are? I'm guessing (as no one else has picked up on the fact it doesn't do that) I'm probably wrong, but interested to get that 1. confirmed if so
& 2. get benefit of other's experience here as to how else it would be connected.

 

[timhoward]

Thanks again Tim and everyone else. UK Power Networks are booked in to go have a look on 18th Feb. Will be interesting to see what they do.
The unsheathed cable disappears under the floor. If it was the DNO earth wouldn't it be a "sweated" connection to the sheath at the top of the cable where the other clamps are? I'm guessing (as no one else has picked up on the fact it doesn't do that) I'm probably wrong, but interested to get that 1. confirmed if so
& 2. get benefit of other's experience here as to how else it would be connected.

It wasn't really possible to see from the photos where the unsheathed cable went.
Various possibilities - it could be sweated on lower down, it could have snapped off and been shoved down the hole by the same person that threw the clamps on, or it could be an or current old water/gas bond.
I think you've done the right thing getting the DNO out. Please do report back!