Replacing single socket with double - attaching box to wall.

[Harry Bloomfield]

Thanks for this. How would I determine the sizes of the cables?

As I suggested above. 2.5mm will be one single copper core strand, 4mm will have seven strands. Often the sheath will also have the size moulded on it to, or at least a type number.

 

[conny]

Hi Harry,

Based on my detective work (and with the help of a tester pen and socket tester from Screwfix) I’ve determined the following:

The two sockets in the study are on different circuits. Socket #1 at my wife’s desk is the one that has 2 sets of wires in it. It’s connected to MCB #7 in the CU, which is 32A and seems to be the ring circuit. Socket #2 at my desk is connected to MCB #1, which is a 16A MCB. The only other socket I can see connected to this MCB is in our guest room, on the other side of the house but in the same position on the wall (back wall, under the window in the corner).

I don’t know which of these two sockets is first in the spur, but I suppose opening it up would allow me to see how many wires there are.

If you are sure the socket by your desk and the one in the guest room are the only ones connected to MCB #1 then take the face off one of them. If it has 2 cables, then check the other one. One of them will have 2 and one of them will have 1. The single cable is the end one and the 2 cable is the first one. Changing both sockets, (the one by your desk and the one by your wifes desk will make no difference whatsoever. Just remember when you are doing them that they are on different circuits so check they are completely isolated before working on each of them.

Thanks for this. How would I determine the sizes of the cables?

Look at Harrys post above, (#85). Odds on, if it is a single copper wire it will be 2.5mm, if it's stranded it will be 4.0mm. You should use the same.
I suspect it will be a single as it is protected by a 16A MCB. If it was 4.0mm stranded it should be protected by a 20A MCB.
As suggested very early on, if the cables seem a bit short, leave the current back box in situ, connect a 6" length of the correct cable to the back of your new double socket. Using wago's, you can now use the original back box as a joint box. Use the 4 corner fixing holes in your new surface mount box to screw it to the wall through the plasterwork surrounding the old box still in the wall.
If there is a tiny gap showing, simply run a bead of decorators' white mastic along the edge of the surface box. It will blend in with the surface box and not be noticeable.
Have faith in your abilities. (Oh, and don't forget the earth sleeving. It's only coppers for a small roll).

 

[EFLImpudence]

We don't do diameters Sam - 2.5 square millimetres (2.5mm²) and 4 square millimetres (4mm²) cross-sectional area.


I must say you lot are not making it easy for Sam.

 

[Harry Bloomfield]

The two sockets in the study are on different circuits. Socket #1 at my wife’s desk is the one that has 2 sets of wires in it. It’s connected to MCB #7 in the CU, which is 32A and seems to be the ring circuit. Socket #2 at my desk is connected to MCB #1, which is a 16A MCB.

That is an unusual set up, normally, all sockets in a room would be on the same circuit, unless there is a good reason for them not to be. No matter, follow the good advice you have already been given and ignore the trolling.

 

[Nope]

That is an unusual set up, normally, all sockets in a room would be on the same circuit, unless there is a good reason for them not to be. No matter, follow the good advice you have already been given and ignore the trolling.

Thanks Harry. I have certainly been given a lot of helpful advice - trolls notwithstanding!

 

[Murdochcat]

That is an unusual set up, normally, all sockets in a room would be on the same circuit, unless there is a good reason for them not to be.

more rubbish.

there are countless properties in the UK with more than 1 circuit in rooms. The most 1 counted once was 4. Properties change over time and practicalities of changes often trumps best practice

having the idea sockets in a room are always on the same circuit is just misleading to say the very least.

 

[SUNRAY]

That is an unusual set up, normally, all sockets in a room would be on the same circuit, unless there is a good reason for them not to be. No matter, follow the good advice you have already been given and ignore the trolling.

This is fairly typical of reconfigured electric heating circuits, especially E7 tariff systems where each room has a heater point and a socket circuit (ring final), also depending on the age of the wiring system many houses started with a radial and one single socket in each room Might have even a BS546 15A! and adding a Ring final may have been easier than extending the radials.

 

[Nope]

Ok everyone. I’ve been looking at all the information available to me and I think I’m going to have another go at this. I have ordered a metre of 2.5mm T+E and another metre of 4mm. I have 2 and 3 core Wago connectors that I will use to join the wires.

Here is my plan of action:
1. Flick off MCB protecting the socket I want to work on then test with socket tester to verify it is not live.
2. Unscrew socket faceplate
3. Unscrew and inspect existing wires
4. Feed existing wires through back of new surface pattress.
6. Attach surface pattress to wall.
7. Extend length of existing wires if needed using Wago connectors and a length of 2.5 or 4mm depending on existing wire size.
8. Connect up faceplate
9. Screw faceplate to pattress
10. Flip MCB back on.
11. Plug in socket tester
12. Breathe!!

Mrs SamH82 needs the study today so I’ll let her work away but I’ll give it a go tomorrow or on Sunday.

Wish me luck!

 

[Harry Bloomfield]

1. Flick off MCB protecting the socket I want to work on then test with socket tester to verify it is not live.

Small reduction in risk, but sometimes it can be safer to isolate the entire supply, on the chance that someone has borrowed a neutral, from the circuit you are working on.

 

[Nope]

Small reduction in risk, but sometimes it can be safer to isolate the entire supply, on the chance that someone has borrowed a neutral, from the circuit you are working on.

Thanks Harry. That did occur to me after I’d posted this. To be safe I’ll hit the main switch then.

 

[LeeJC]

Full isolation is going to be the absolute safest method, although it’s still good practise to confirm dead.
Your plan is sound and sorry to harp on but again make sure those screws in the back of the socket are tight.
If you’ve got 2 cables then tighten down on them, if you find a single then I believe good practise is to double over the conductor.

Good luck mate.

 

[Nope]

Full isolation is going to be the absolute safest method, although it’s still good practise to confirm dead.

Thanks for that. As I said to Harry it did occur to me after posting that I should switch everything off, so I will do! As for “confirming dead”, I have a socket tester and no contact pen tester from Screwfix so I’ll use these before turning off power and once again after turning off. I’m always naturally quite paranoid/anxious about working with electricity - call it survival instinct!

Your plan is sound and sorry to harp on but again make sure those screws in the back of the socket are tight.

I don’t think you’re “harping on” - you’re trying to help me make sure it’s done properly, which I appreciate. Your advice and that of others has helped me create a useful checklist.

If you’ve got 2 cables then tighten down on them, if you find a single then I believe good practise is to double over the conductor.

Thanks, I’ve seen this done in existing switches that I’ve been replacing so I’ll be sure to do it myself.

Good luck mate.

Thank you!

 

[LeeJC]

Oh another thing

On the Wago box there are details/measurement for the length of stripped conductor required for the connector. It ensures you’ve got the insulation inside the body of the wago.

That really is it from me now

Honest.

 

[Nope]

Oh another thing

On the Wago box there are details/measurement for the length of stripped conductor required for the connector. It ensures you’ve got the insulation inside the body of the wago.

That really is it from me now

Honest.

Thanks Lee. You have been extremely helpful.

 

[Nope]

And the job is done!!!

The socket by my wife’s desk (with the flowery wallpaper) was the one on the ring, so I just used a three core Wago and a length of 2.5mm T+E to extend the wires.

The socket by my desk (painted wall) has only one set of wires in it. Given what I know about my house wiring that’s the first one on the radial connected to MCB #1.

Used the socket tester to test it and got 2 greens and a steady tone, so all good!!!

What’s my next DIY Electrical project?