Extra wires in back of socket pattress?

Discussion in 'Electricians' Talk' started by James84, Nov 5, 2020.

  1. James84

    James84 New Member

    Afternoon,

    In the process of redecorating my daugters bedroom and the next phase is to get someone in to do some electrical work. The room has 2 single sockets which I wanted to change to doubles and I also want a spurr off one.

    Opened them up and found that each socket has 2 live, 2 neutral and 1 earth as I would expect but in the back there is also an extra live and neaural wire that feeds into the back of the pattress box and straight back out again. What is this and why is it there? Just want to check before I go out and buy extra plug sockets for the job.

    Thanks,
    J
     

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  2. Bob Rathbone

    Bob Rathbone Screwfix Select

    This is a loop in conduit system where one run of 20mm conduit visits all of the socket outlets, it looks like a radial circuit from the conduit POV, but 4 wires 2 red, 2 black are run from the ccu to the last outlet, lets call the one pair of red & black circuit 'A' and the other pair circuit 'B'. At the first outlet pair 'A' are pulled into a loop for the socket, at the next outlet pair 'B' are pulled out, and so on to the end. This ensures that the outlets are evenly distributed around the ring.
     
  3. James84

    James84 New Member

    Evening Bob,

    Thanks for taking the time to reply, must admit I seem to be a little more confused than I was originally (but thats not hard). From the above, I'm picking up a couple of buzz words. I note you mention both radial and ring, so what circuit do I have, a ring or radial? Based on my limited understanding, my 2 in and 2 out signified a ring, but it was this loop in the bacl that confused me.

    Bottom line, can this wiring still be used to spurr off in the normal manner? Basically, am I ok to buy the stuff needed in advance of getting the electricion round? I do have a socket in the hall that is a spurr from another room. This particular socket has the loop in the back like above but 3 live and 3 neutral wires coming out.

    Thanks,
    J
     
  4. Bazza

    Bazza Screwfix Select

    This isnt going to as easy as it first appeared!
    You only have a single back box there. To change it to a double you would need a double box
    BUT
    that single box is firmly part of the conduit system and it will be the devil's job to remove the single and swop it for a double. It may be easier to sink a separate single back box next to the existing and connect it as a spur.

    Or use a "convertasocket" - this is a double socket that fits on a single box. They look cack (IMO) but do the job.

    Well..it might be a ring, or it could be a radial circuit with that socket just not being at the end. Only testing will reveal.

    I think that your best option is
    1. not to buy anything
    2. get an electrician to decide how this can be tackled

    Finally, (I'm sorry) the layout indicates an elderly installation. New sockets must be RCD-protected.
    Elderly installations did not include RCD-protection when they were installed. So you need to check if the consumer unit/fuseboard has been updated to provide RCD-protection.
     
  5. The Happy Builder

    The Happy Builder Screwfix Select

    If that’s a installation with conduit, what is securing the galvanised steel back box to the conduit?
     
  6. Bazza

    Bazza Screwfix Select

    The conduit is!
     
  7. The Happy Builder

    The Happy Builder Screwfix Select

  8. The Happy Builder

    The Happy Builder Screwfix Select


    With what?
     
  9. James84

    James84 New Member

    "This isnt going to as easy as it first appeared!" - God dammit, you ruined my evening!!

    Thank you all for your replies, will get a sparky out to have a look. I do have a modern (or what i would call modern) CCU, was installed in 2013 so thats something!
     
  10. Alan sherriff

    Alan sherriff Active Member

     
  11. Alan sherriff

    Alan sherriff Active Member

    As an apprentice we called it wire one miss one very common method of wiring ring finals
     
  12. Severntrent

    Severntrent Screwfix Select

    Interesting James, as I understand it from Bobs description, basically imagine you have 2 twin and earth cables running from CCU up your conduits and passing through each back box right to the last back box. Alternate cables are cut at the next box as you work towards the last one and the socket connected. Obviously forget about it being twin and earth as its wired up in single cables but it hopefully gives you the gist of the arrangement. No doubt I will be corrected if this simple explanation is off the mark.

    As for making it into a double socket I would have no problem with cutting the side of 1 box off with a multi tasker, similarly with a new single box and fixing the new bit in place so a double back box is formed. I doubt whether an electrician would have the patience and dare I say skill to do it. No doubt they will also tell you what reg this breechs and that you are not allowed to play with the electrics, or gas,or windows, etc etc
     
  13. James84

    James84 New Member

    Interesting, so are we saying that we have the wires running all they way to the last plug in the socket before doubling back on themselves and connecting up? Superbly put together and professional illustraion attached!
     

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  14. candoabitofmoststuff

    candoabitofmoststuff Screwfix Select

    No... not quite right...
    The cables go through all the points, but along the route alternate sockets are connected... As Alan Sherriff said "wire one, miss one"

    Try again with your diagram!

    Cando
     
  15. James84

    James84 New Member

    How about this one? So does this mean i definitley have a ring circuit or could this still be a radial circuit?

    J
     

    Attached Files:

  16. Bazza

    Bazza Screwfix Select

    The conduit is fixed to the back box. This can be through several methods including a threaded bush. This sort of thing
    1ABC5B6B-6643-4C8F-BF4C-58FCAA5B5EDD.jpeg
    Sometimes the bush is an integral part of the back box. In the end the box and steel conduit are securely fixed together. The conduit is then cemented into the wall. The box needs no other fixings.

    Also, in this type of installation, the conduit is the earth. Its very secure connection to the back box provides the earth for the socket. If you look at the OP’s picture, you’ll see the earth (sleeved in green) connected from the back box to the socket’s earth. There is no separate earth wire run through the conduit.
     
  17. The Happy Builder

    The Happy Builder Screwfix Select

    If it’s conduit it should be attached to the back box with a bush, all you need to do is cut out around the existing box to free it up and make room for the new double box, then undo the bush, fit the new box and refit the bush.

    Screwfix sell a special spanner, but it can be done without one.

    https://www.screwfix.com/p/c-k-conduit-bush-wrench/5686K
     
  18. Bazza

    Bazza Screwfix Select

    Bearing in mind that the OP would need to cut the looped conductors and reconnect them. And properly maintain the earth for the conduit both to the socket and on to the second conduit.
     
  19. The Happy Builder

    The Happy Builder Screwfix Select

    And patch the plaster.
     
  20. James84

    James84 New Member

    Plastering is something I can do, that job won't kill me ;)
     

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