Light circuit cabling

Discussion in 'Electricians' Talk' started by Joel Cramoysan, Aug 8, 2022.

  1. Joel Cramoysan

    Joel Cramoysan New Member

    Hi guys,

    First time poster. Apologies for the long post but have tried to be as thorough as possible!

    I am no stranger to electrics but I work on a boat so am unfamiliar with UK domestic wiring and circuits.

    I'm wanting to replace a 2 gang switch with a smart switch. Only one of the circuits (hallway) is switched (controlled from two places if I've understood the definition correctly). The other circuit is for the outdoor light by the front door and is only controlled from this switch.

    I have red, blue, yellow and earth.

    First off I'm trying to figure out if I have a neutral as that will dictate what type of switch I buy. According to old convention, red is live (confirmed), blue should be neutral and yellow is "other" - I'm guessing that's the load wires?

    However, yellow and blue all have brown sleeves which I'm inclined to think is indicative of something else - perhaps to do with the switched circuit?

    Measuring red to earth is 240V at all times (confirmed live). However it is for some reason jumped across into what appears to be an empty terminal labelled common.

    Blue to earth is approx 4V when lights are off, 240V when only hallway light is on, 6V when only outside light is on. So blue is not neutral??


    Yellow on the right in the picture - to earth with lights off = 33V?? With outside light on = 240V. With hallway light on = 36V??

    Yellow on the left - to earth with lights off = 5V. With hallway light on = 240V. With outside light on = 6V

    So I think I've confirmed yellow cables go to the lights? But some strange voltages on the right one.

    Overall the more I think about it, the more confused I get! Could someone please help by telling me what each of the cables are actually for, whether the voltages I'm getting make sense, and how I would translate this into a smart switch?

    Thanks in advance!

    20220808_113659.jpg 20220808_113728.jpg
     
  2. Hans_25

    Hans_25 Screwfix Select

    I'm rusty, but think one of those switches is a two way switch. All are lives from what I can see, brown sleeve indicates a live (either perm or switched live).

    So no don't think you have a neutral there as all cables are live.
     
  3. terrymac

    terrymac Screwfix Select

    They are strappers for the two way , and all line conductors. No neutrals.
     
  4. Joel Cramoysan

    Joel Cramoysan New Member

    Cheers guys, appreciate the response.

    No neutrals is good to know!

    @terrymac, what are strappers? Terminology I'm not familiar with!

    Any ideas on the voltage readings, particularly 33V / 36V?

    So why are blue together and yellow separate?
     
  5. terrymac

    terrymac Screwfix Select

    Strappers are the 3 line conductors that go between the two switches in a two way lighting set up.
    The lower voltages present are likely induced voltages.
     
  6. Joel Cramoysan

    Joel Cramoysan New Member

    Hi Terry,

    Please do bare with me if I'm being thick here...

    But from my testing, one yellow is live when the outdoor light is on, and the other is live when the landing light is on. Also the outdoor light is definitely not two way, only the one switch.

    And then blues are connected together from different cables but only live when the landing light is on...

    I'm really struggling to picture it in my head... Would you mind doing a really dicky basic line diagram please?? I know I'm asking a lot...
     
  7. terrymac

    terrymac Screwfix Select

    The wiring is a little odd to be frank. Are both switches on the same circuit breaker (or fuse )at the consumer unit
    ( Or fuseborad) ?
     
  8. chesterw

    chesterw Well-Known Member

    Bottom switch - the reds are permanent live (including a strapper), the yellow with brown sleeve is switchline
    Upper switch - the two blues - one is a strapper and the other is the switch line, the yellow is another strapper
     
  9. Joel Cramoysan

    Joel Cramoysan New Member

    Glad it's not just me that finds it odd! Haha.

    Yes both circuits are fed from the same CB.
     
  10. Joel Cramoysan

    Joel Cramoysan New Member

    Hi @chesterw, thanks for the reply!

    OK I'm getting even more confused now haha.

    Why is there two yellow cables, both with brown sleeves, doing different jobs? From my measurements it seems yellow is outgoing live to the light??

    I'm so used to the wiring on my boat now where everything is phase and neutral which makes it so much easier... Where even is the neutral, on the other side of the light?

    To be absolutely frank, the more I think about it the less I understand it. Why is there even 3 cables? Live in to one side of the switch, outgoing live to light bulb on the other side would do it wouldn't it?

    If anyone has the time and can make sense, I'd really appreciate a basic wiring diagram...
     
  11. Joel Cramoysan

    Joel Cramoysan New Member

    Yeh I guess there must be! Hallway is 3 LED spot lights with no easy access to find something up above.

    So in general then, using my hallway as an example, there will be a live into a switch, then the outgoing side of the switch (switched live) goes to the first light. Then you'd have a live cable jumped from first light to the second light and on to the 3rd one... With a neutral taken off the other side of each light back to a JB somewhere??

    And then back to my 2 gang switch... Would you say the yellow with sleeves are the switched lives - one to hallway circuit and one to outdoor light?
     
  12. chesterw

    chesterw Well-Known Member

    There is nothing odd about this wiring, it is quite normal and everyday, and anybody with basic electrical knowledge should be able to draw it and understand it
     
  13. terrymac

    terrymac Screwfix Select

    You have two 3 core and earth cables.
    One goes from the switch in your pic ,to the other ( remote ) switch for hall light.
    The other 3 core& earth goes to the hall ceiling lights rose/ connections.
    The 3 line conductors are ..
    Permanent line.
    Switched line for hall light.
    Switched line for outside light.
    At this point the switched line to outside light ,together with a neutral,would be fed to the outside light.
    Edit. I deleted my previous post that you quoted ,as its a bit misleading. Hopefully above is clearer.
     
    Joel Cramoysan likes this.
  14. Ind spark

    Ind spark Screwfix Select

    Hope this helps, I need to get a life;)
     

    Attached Files:

  15. Joel Cramoysan

    Joel Cramoysan New Member

    Hey Ind Spark, thanks for taking the time! Unfortunately the last word on B Yellow is missing - "common to common L..."?

    It does help but I'm still not 100% there and it's melting my brain...

    For the outside light, we have a permanent live (red), then switched live (blue) and neutral (yellow)?

    Also I've just noticed that the yellow core of the cable you have labelled as B is connected into a terminal which is labelled common if that changes anything?
     
  16. terrymac

    terrymac Screwfix Select

    The yellow in A is connected to the outside light switch !!
     
    Joel Cramoysan likes this.
  17. Joel Cramoysan

    Joel Cramoysan New Member

    Thanks @terrymac for continuing to help... Are you able to attribute colours of cores to your description please? Using the numbers in this pic...

    20220808_113659.jpg

    I feel like I'm almost there and this should cement it...
     
  18. Bazza-spark

    Bazza-spark Screwfix Select

    This diagram shows both upstairs and downstairs lights as 2 way, however yours is only the upstairs, but essentially this illustrates what you have.

    upload_2022-8-8_16-13-3.png

    In this case your blues are represented by the grey cables
    Your reds by the brown cables and
    your yellow by the black cable.
     
    Last edited: Aug 8, 2022
    Ind spark likes this.
  19. terrymac

    terrymac Screwfix Select

    Bazza ,the op has a hall light ( two way) ,and an outside light ( one way).I suspect your diagram may confuse him greatly...
    Nice as it is !!
     
    Hans_25 likes this.
  20. Ind spark

    Ind spark Screwfix Select

    Sorry all, yes yellow to outside light.

    I assume it's been done this way as to have only 1 cable at the outside light, there will be some connections in the hall light.

    Don't they have 2 way switching on boats:p
     

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