In message ,
ARWadsworth writes

Guess what job I am doing later in the week?

I got a phone call off a bloke complaining the metal backbox in the new
bathroom shaver point that he has fitted lights up his neon
screwdriver. His further tests showed that the same happens in one of
his bedroom lightswitch metal backboxes.


I had something vaguely similar a couple of years back on my fathers
home, 200 miles away from me and in the middle of nowhere, overhead
power lines.. He was getting tingles of anything that should have been
earthed. Kitchen sink, water radiators, metal clad switches etc. It was
"interesting"

A rather fast 200 miles later........

Measuring between live and earth in the CU showed only a couple of
volts.

At the CU there was a rather old earth leakage trip, one where the earth
passed trough a separate unit to a local earth stake and any earth
current caused the trip to break the incoming supply. This had failed
and was happily still supplying the house with power.
( now replaced with something more substantial, looked like a token
gesture and probably once relied more on the lead water pipe, also new
CU with rcd now fitted )

If it had been the old days when he had a lead water pipe then it would
have either blown a fuse or warmed up the water!!

The reason for all of this was that in his green house he had trapped a
cable under a propagating frame and the VERY old rubber cable had
disintegrated inside and the live was short to the earth. There was no
separate earth to the green house it relied on the house earth via the
SWA that connected the two. The couple of volts measured at the CU were
I assume the drop in the SWA.



The moral of this is that
a) equipotential bonding works! Fine in the main house, not so sure
about the green house though with all its water and wet floors.
b) don't trust elderly, 90 year old, fathers to look after their own
electrics. c) there is a God out there looking after gardeners.

It was an interesting experience..................................
--
Bill