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Yet another 2W lighting conundrum (and why I don't like domestics again)

Discussion in 'Electrics UK' started by SUNRAY, 9 Oct 2019.

  1. SUNRAY

    SUNRAY

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    Another simple - just change a light switch job.

    Customer reports a big flash, tripping and lights not working.

    I arrived to find an obvious brand new 2G switch with a big black flash mark and didn't move properly. Customer insists it has not been touched despite some debris below on the otherwise clean carpet.

    I found 5 cables, only No5 having an earth wired with cables 4&5 going off to a couple of 1G switches thus:

    upload_2019-10-9_14-54-2.png
    I noted the connexions and numbered cables as above then removed the faulty 2G switch
    Cable 1 = 40Ω r-bk, 2Ω bk-earth, 43Ω r-earth. (Main switch in fuse board removes earth readings)
    Cable 2 = 120Ω r-bk
    Cable 3 = 41Ω r-bk, 76Ω y-bk, 139Ω r-y
    Cable 4 and switch buzzed out perfectly
    Cable 5 and switch buzzed out ok except grey was open circuit and switch didn't move properly.

    The 2 associated ceiling roses looked like they are from the 60's with untold layers of paint, as is much of the installation.

    And to crown it all there was a power cut.

    I have fixed this and sent a report to the managing agent pointing out the importance of regular reports and the need for updating what's installed.

    Ideas anyone?
     

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    Last edited by a moderator: 9 Oct 2019
  2. securespark

    securespark

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    Perhaps I'm tired, but I don't understand your diagram! Sorry....:(
     
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  3. AndyPRK

    AndyPRK

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    I think the switch that was messed with goes between 4 and 5


    is this the clue then?

    "No5 having an earth wired with cables "

    The earth was connected to the live connections ?
     
  4. AndyPRK

    AndyPRK

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    where do you get cable, that has the colours of cable 3 ?
     
  5. winston1

    winston1

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    You need a Tardis.
     
  6. EFLImpudence

    EFLImpudence

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    I am with Secure.

    What are we looking for?
    Are the stars connections? If so, why not use the switch terminal on the lower circuit?

    Upper looks like a conventional two-way circuit (even though three strappers) with 2 black connected to switched live.
    Lower looks like a conversion two-way circuit with 2 red and 3 red connected to the common strapper.
     
  7. SUNRAY

    SUNRAY

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    Delorean
     
  8. SUNRAY

    SUNRAY

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    Cable 1 buzzed out as the supply and by going round the house found one light switched on, I took this to be 'loop in'.

    checking cable 2 for resistance I found there are 2 additional lights, I took this to be 'loop out'.

    After I took the resistance readings on cable 3, by removing the bulbs relevant to the 2G switch and found the yellow is a 60W bulb for the upper switch and the red is a 100W bulb for the lower switch on a common black neutral.

    As I renewed the switches I found: Red of cable 4 is too short to reach 'lower com' and black of cable 5 is too short to reach 'upper com' to do the 3 strapper method.

    by making it 3 connexions different (and one extra joint) to how I found it, this works:
    Detling 2G 2W switches solution.gif
    I had a 300VA interter with me and managed to function test.
     
  9. JohnD

    JohnD

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    I have some.

    I am not alone.
     
  10. securespark

    securespark

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    I had some red white and blue three core but sadly lost it.
     
  11. SUNRAY

    SUNRAY

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    It used to be one of the regular colour options
    [​IMG]
    Still got a bit installed in my house
    [​IMG]
     
  12. AndyPRK

    AndyPRK

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    Arh yes. We went thru this before.

    I recall the pic which had the white in it
     
  13. securespark

    securespark

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    Say what you like about older wiring, but those dove-tailed ply-backed boxes were very nicely made.
     
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  14. SUNRAY

    SUNRAY

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    And very nicely staying put until an earth is available :whistle:
     
  15. securespark

    securespark

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    Of course!
     
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