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Lighting question

Former Community Member
Former Community Member
So today I wanted to add another switch in a house.


The extra switch would need to now include an intermediate due to it being already 2wY.


now when I took the switches off, one switch the common has just a single sheath core, the L1 and L2 are a 2 core cable L1 being Red and L2 being black.

This is exactly the same in the other switch.


I thought this must mean there is a JB somewhere ? In the light fitting there is 3 T&E, and 1 single cable which goes into the lamp live! 


I just can’t understand how this could be wired? 


Any ideas?
  • 0

    I'm pretty sure there will be a Joint Box (JB) hiding somewhere under the floor or in the walls.



    More likely the single core permanent L has just been 'borrowed' from another nearby switch (on the same circuit if it's been done nicely) - saves a few of metres of cable over taking it from the rose. No JBs required.


       - Andy.
  • 0
    All the other questions were to try and determine the likelihood of the live having been taken from a different circuit to the one the neutral is connected to at the light, it is possible that may be why there is more than one lighting circuit all on the same RCD.


    Turn all the lighting circuits off whilst you are working and check there’s nothing live in the switch box when you are working.


     Andy Betteridge
  • 0
    Is it a two plate system?
  • 0

    Is it a two plate system?



    Partly - it sounds more like a bit of a hybrid between 2-plate and 3-plate. The ceiling roses appear to have been provided with perm L & N - 3-plate style, but this particular switch may well have been looped from another switch 2-plate style. I recall our house being re-wired using just such a 'style' in the late 1970s. If it was really done properly the single cores (Ls at least) carried a c.p.c. too.


    Not to be recommended these days of course - unless done very carefully the EMI resulting from single core cables carrying unbalanced currents around large areas isn't ideal.


       - Andy.


  • 0

    AJJewsbury:




    Is it a two plate system?



    Partly - it sounds more like a bit of a hybrid between 2-plate and 3-plate. The ceiling roses appear to have been provided with perm L & N - 3-plate style, but this particular switch may well have been looped from another switch 2-plate style. I recall our house being re-wired using just such a 'style' in the late 1970s. If it was really done properly the single cores (Ls at least) carried a c.p.c. too.


    Not to be recommended these days of course - unless done very carefully the EMI resulting from single core cables carrying unbalanced currents around large areas isn't ideal.


       - Andy.


    I was also thinking... live / feed, one end... switch line the other, with intermediates in between... all you need is a pair of strappers... would be interesting to see it!

     




     

  • 0
    Sounds like a bog standard Loop in at ceiling rose jobby. The singles (or single and earth?) to C might be from a JB somewhere converting T & E to Singles or, as said, might be pinched of other switches. So the 3 x T & E might be loop in, loop out and switch or it might be loop in and two loops out i.e. a "tree circuit". You could take strappers from existing switch or a JB and, if 1 gang switches existing, you might swap one for an intermediate.Two lighting MCBs  on one RCD does point to possible "borrowed N" it was quite common in the day (I never liked it meeself).

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