UK house, all sockets upstairs have 3 sets of cables connecting

Question

I was planning on adding a spur from a socket in my house (in the UK). On removing the socket I would have liked to spur from there are 3 sets of cables connected to it (3 live, 3 neutural, 3 earth) as such it looks like a ring main with an existing spur.

On checking the other sockets upstairs in an attempt to find where the spur is going, all but one socket have 3 sets of wires connected except one (the hallway socket) which has the usual 2 sets for a ring main.

The house is c1930 and would have been wired at a later date. Wiring is pre 2004 using Red/Black for Live/Neutural. Cables look to be 2.5mm2 and the MCB's are 32a so appear to be ring main rather than radial.

Any ideas on how the sockets are wired as this doesn't look like a standard ring main as the third set of wires for each socket don't appear to be going to a spur.

We have seperate MCB's for each floor and there aren't enough sockets downstairs for these to all be spurs going down.

Any help and ideas are much appreciated. I'll hold off on the original spur idea as it doesn't seem as plain cut as I hoped.

Answer 1

It certainly doesn't sound like standard ring main wiring. It could have been done by an amateur (like, sadly, a lot of domestic wiring) or they could be spurs to sockets that were never fitted or that you can't see because they're hidden away or used for fixed outlets like towel rails, fans, wall mounted TVs, run into the roof space for aerial boosters, etc. etc. Or they may have used extra segments of cable to join sockets together in some weird scheme to beef up the ring if there are long runs between sockets and they were worried about voltage drop.

The first thing would be to switch off the MCB and check every electrical item in the house to see if anything goes off that you don't expect, which might be enough to explain what's on the end of some or all of these spurs. How many cables originate from the MCB?

But the only way to be fully sure would be to disconnect the whole lot, including from the MCB, and use a meter to identify the two ends of each segment of cable. Once you've established which segments make up the ring you can see which ones are spurs and try to find what's on the end of each one. A genuinely unused spur could be left disconnected and your own spur connected in its place.

Answer 2

Have you looked at the sockets downstairs?

One cheap (and nasty) approach to wiring houses with solid downstairs floors was to put the upstairs sockets on a ring (or maybe two rings), and then take spurs from the upstairs sockets to supply the downstairs ones.