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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.

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  • European standard neutral is blue. Red and black is for DC. So it s DC or wrong colors.
    – user263983
    Dec 28, 2021 at 14:06
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    @user263983 As OP says, this is mains AC wired in old UK colours - red for live, black for neutral - prior to EU harmonisation.
    – Finbarr
    Dec 28, 2021 at 14:51
  • To confirm, this is about the older UK AC colour coding of Red for Live and Black for Neutural. Not sure about other countries but pre-2004 this was the standard wiring colours in the UK. Dec 28, 2021 at 17:36
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    OK so when you service a circuit, you switch off the circuit breaker, right? When you do, does it also kill the room lights or other hard-wired loads? Dec 28, 2021 at 23:06

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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.

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  • Many thanks Finbarr, I'll get the multimeter out in the morning when there's some natural light again and try to source where the possible spurs are going. With the cover on the consumer unit there are 7 2.5mm2 cables coming out. At a guess this would be a ring main for the kitchen, downstairs and upstairs. The odd cable is likely going to the backup heater on the emersion (heated by the boiler with an electric backup). I can also see 2x 1.5mm2 which will be for the lighting circuits and 2x 4mm2 which will be the cooker and electric shower. Dec 28, 2021 at 17:32
  • We purchased the house from the council and are the first private owners so all electrical work "should" have been carried out by the council, which in itself doesn't provide much confidence! We are planning on having a loft conversion done within the next year so will require new circuits and a larger CU. If the wiring is non standard or doubled up to cope with the load then it may be the best time to have the house rewired while we're at it. Dec 28, 2021 at 17:33
  • The only hard wired appliances are a couple of extractor fans (kitchen and bathroom), boiler (most likely on the kitchen ring) and the aformentioned water tank. Fingers crossed it's just unused spurs which can safely be removed. Dec 28, 2021 at 17:33
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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.

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