Robin wrote:

On 29/05/2020 12:38, Roger Hayter wrote:
snip

It's slighly interesting. The person who wired my house originally
took equipotential bonding remarkably seriously and throughout the house
(at least in all rooms with any CH pipes or extraneous metal work which
I think was everywhere except the conservatory) he ran a network of
10mm insulated earth wire in parallel with every bit of the socket
wiring plus to every pipe, even ones connected by copper back to the
boiler. If I felt like burning the insulation off I'd have about 10kg
of copper I've ripped out doing other jobs. A consequence was an earth
terminal block in almost every room and the electrician used one of them
which was actually directly connected to the supply earth block, rather
than pulling a new wire in from the supply board to do the one bit of
bonding the original owner forgot, which was the oil feed into the house
- one of very few that was actually required. Though since it goes to
the outside oil tank with no earthing to speak of it therefore creates a
new PME hazard. In the context a label saying this connection is
actually wanted might be sensible, though it would have to say why in
the context of dozens of other pointless earth labels.



Others may know what was behind that. To me it sounds like someone (a)
installing high integrity earthing without understanding what was and
wasn't required or (b) with an awful lot of 10mm green/yellow single to
bill to an unsuspecting client. Any idea when it was done?

About 40 years ago, by the householder. He had other wiring quirks.

--

Roger Hayter