Earthing

[John Rumm]

It may be that your meter tails were only 16mm^2 - they quite often downgrade main fuses in that circumstance.

[John Rumm]

A 5 ohm earth is a danger on a normal domestic ring circuit - you may not get enough fault current to clear a fault on a 32A MCB.

[js.b1]

No changing the fuse will not alter the Zs.

However the DNO may have a problem getting Ze low enough.

Under TN-C-S both L-N & L-E are the same because they are Combined in the cutout. A high Ze on TN-C-S may mean a L-N fault disconnect time is slow on a 100A fuse (never mind voltage drop at full load), and as a result they may want to reduce the main fuse rating. Having the correct sized meter tails becomes particularly important if fault disconnect time is beyond that expected.

DNO do reduce the cutout fuse when TN-C-S Ze is above 0.35ohm and some are. A DNO can simply withdraw their earth provision on safety grounds under ESQW2002 or downgrade the service fuse rating to that originally supplied when the initial connection was made.

That was the argument made to me by SP. He could have been talking out of his buttocks, but that is my distinctive competency usually (particularly after plastering, I want something you peel off a roll like pastry).