Practical advice on adding a socket to ring main

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well obviously if it were a 4mm to start with, hopefully they would stop and think, and use the same cable.

In other posts we have heard that if you can satisfy yourself that the cable will not be overloaded, you can use 2.5mm (e.g if its not in a kitchen or util)
 
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well obviously if it were a 4mm to start with, hopefully they would stop and think, and use the same cable.
You did say "I wonder if sparks in the real world use 4mm in this way" so hopefully they should be past the "stop and think" stage.

In other posts we have heard that if you can satisfy yourself that the cable will not be overloaded, you can use 2.5mm (e.g if its not in a kitchen or util)
Have we?

How do you do that with four (two double) sockets?
 
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In other posts we have heard that if you can satisfy yourself that the cable will not be overloaded, you can use 2.5mm (e.g if its not in a kitchen or util)
I'm not sure what you're talking about there. It would never be acceptable to use 2.5mm² cable for a 32A radial sockets circuit.

Are you perhaps thinking of the fact (as EFLI often points out) that if one can convince oneself that a particular load (say, an oven) is "unlikely to result in an overload" then one does not necessarily have to have overload protection at all (only fault protection)? However,m that clearly can only apply to a hard-wired load (whose characteristics are known), not to a sockets circuit (into which 'anything' could be plugged 9n).

Kind Regards, John
 
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1) To extend a ring the best method I have found is use a quad grid plate (same size as double socket) and fit two grid sockets, it means you lose the switch, but you then have a socket to terminate both sides of ring so you can take a cable from each socket to extend the ring.
2) Should it prove not to be a ring, same plate can be made into a socket and fuse connection unit plus either switch or blank.
3) To extend a ring my first thing is plug in the loop impedance meter and record the readings, this means I don't have to open consumer unit after to test, as I now know what loop impedance I can expect, there are other methods. I will also consider if the readings show likely two much cable already.
4) With power isolated, and I mean isolated not simply turned off at the MCB, I can then remove socket and test, checking the line, neutral and earth are not connected assuming everything turned off or unplugged, and I have continuity between lines, neutrals, and earths showing connected in a ring, if a suspect home I will record and compare with readings at CU to ensure no fig of 8, but that is rare.
5) Add extra sockets.
6) Retest the loop impedance figures if a wire has come off when refitting the socket I will see a sharp rise in the loop impedance.
7) Make out the minor works certificate, not only does this show others I am satisfied with work, but acts a a check list so I don't miss doing any tests.

Since you likely don't have a loop impedance tester you need to modify method, either you take a chance that when you replaced last socket nothing popped out, or you test at the CU. However there is always power in the CU so that involves some danger, you need to assess the risk.

Although a multi meter has an ohms range, measuring 0.35 Ω is rather hit and miss, should have 250 mA flowing to measure, you will not get that with a multi-meter, same for the insulation tests, should use 500 volt, with 9 volt of a multi-meter again better than nothing but you may miss things. Although the EZ150 plug in tester has a loop test, it is not good enough to use the short cut method I use in testing still a ring.

However fitting a FCU and fused spur the increase allowed with the loop impedance means unlikely to exceed the limit, if not already RCD protected you can use a RCD FCU, so with the reduced ability to test, the fused spur is likely a much safer method to add more sockets.

Even in my own house I have not tested and inspected as much as I should, and found I have two independent faults on the final ring, I need to lift floor boards and get other access, so I have simply fitted a 20A MCB instead of the 32A MCB until I have assess to find the fault. How I got two independent faults I don't know, not seen rodents, but it has happened, so I need to fix it. Lucky I do have the meters, and whole house RCD protected.
 
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True, but the OP was clear that he wanted the new sockets above the existing one (and 'maybe offset to right or left').

Kind Regards, John
So it depends how far offset, doesn't it. Your reply implied that it could not be more than the width of a socket.
 
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As the walls are dot and dab glue permitting can't I just fish the cable in the void and chase out for the back box rather than open the wall up?
What is the typical thickness of a splodge of adhesive?

What is the surface of the wall behind the boards like?
 
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So it depends how far offset, doesn't it. Your reply implied that it could not be more than the width of a socket.
Well, it can't can it? (it fact, it needs to be a bit less than 'the width of a socket). There has to be at least some 'overlap' between the existing socket and one of the new ones above it, in order for a (vertical) cable between the two to be within a safe zone throughout its length, doesn't there? The second new socket would then have to have either a vertical or horizontal 'overlap' with the first new one - but, with that provisio, could be as 'offset' as one wanted.

... or have I misunderstood what you are saying?

Kind Regards, John
 
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Well, it can't can it? (it fact, it needs to be a bit less than 'the width of a socket). There has to be at least some 'overlap' between the existing socket and one of the new ones above it, in order for a (vertical) cable between the two to be within a safe zone throughout its length, doesn't there? The second new socket would then have to have either a vertical or horizontal 'overlap' with the first new one - but, with that provisio, could be as 'offset' as one wanted.

... or have I misunderstood what you are saying?

Kind Regards, John

Your assumptions are correct the offset would be about half a socket to the left of the existing one and the second socket would be horizontal to the new raised socket.

If I do decide to go down the ring main option can I run a new cable from the new socket to the next socket along to complete the ring through the back box of the original socket? I suspect the answer is no as I have never seen this but I stand to be corrected.

Thanks
 
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Your assumptions are correct the offset would be about half a socket to the left of the existing one and the second socket would be horizontal to the new raised socket.
Thanks for confirming.
If I do decide to go down the ring main option can I run a new cable from the new socket to the next socket along to complete the ring through the back box of the original socket? I suspect the answer is no as I have never seen this but I stand to be corrected.
If I understand you correctly, then that is precisely what I suggested, and is fine provided there is room in the existing socket's back box for the necessary connections. I'll see if I can produce a sketch for you.

However, as has been said, a single 4mm² 'spur' to both new sockets would probably be the simplest method.

Kind Regards, John
 
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You can replace the existing double socket with a pair of singles in a dual box and then run two cable up to the new sockets.

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