As mentioned in my "soundproofing and AV cabinet in the chimney" thread
I'm relocating the mains and aerial boxes from the party wall, and while
doing so adding some extra sockets to the ring.
At the weekend I was ready to remove the final old socket and insert my
loop of extra sockets, so I'd isolated the CU, did a check L->L, N->N
and E->E around my new loop which was OK, then I did a similar check
around the existing ring at the point I would join into it ... live and
neutral OK, but oh dear, no continuity round the earth!
Spent bloody hours over the weekend (in bursts of a few hours so the
fridge/freezer wasn't off for too long at a time) with temporary shorts
between E/L or E/N at various points to trace where the circuit went,
and whether the fault was up or downstream of those points, checking
junction boxes under under floorboards which I knew were there, finding
one I didn't know existed, remembering sockets that were behind
wardrobes that haven't been used for years etc, what a ball-ache.
Finally today traced it to the cable on the ring that's between one
socket in the back bedroom and another socket in the front bedroom on
the same wall, cable goes down wall, under floor, back up wall, it's
plastered over, can't see if there's metal capping over it, but I
imagine so, similar cables in other original parts of the house are,
I've never done any work along the route of the cable, and can't see
where any previous owners have either.
There's a convenient loose floorboard (I presume from when the central
heating was added) about midway between the sockets, where I can poke a
torch and a mirror on a stick down, no damage to the cable where it's
visible, so I conclude it has probably been like it since the house was
built in ~1976.
Getting access to the cable at either end is a bit of a problem at the
moment, back bedroom is chock-full of stuff while I'm working on many
other parts of the house at once, front bedroom there's a large wardrobe
in front of the socket which I can barely move, and there's nowhere to
move it to at the moment.
So for /now/
I have put it all back as it was, knowing that every socket
is earthed, some from one direction, some from the other. There's
nothing which is a "high powered" appliance on this ring (I put a second
ring in just for the kitchen and garage a few years ago) in fact it's
probably only the fridge and boiler which aren't double insulated
I suppose I could deliberately split the ring at one of the junctions,
and replace the 32A MCB with a 20A MCB and call it a radial instead of a
ring (that just happens to have the CU at its centre).
Not having a trained monkey to assist with going round with the
multimeter while adding/removing shorts made it a slow job, in fact I
thought it might be worthwhile knocking up a battery powered box to
toggle a set of relays in a sequence, so you could wire it in and it
would give e.g. one brief short from L/E followed by two longer shorts
from L/N to cut down the number of trips up and down the stairs and
squeezing behind furniture etc, does a similar testing device exist?