Electrics

Discussion in 'Getting Started FAQ' started by BEF, Mar 22, 2020.

  1. BEF

    BEF New Member

    Hi, I am not an electrician but a competent DIYer.
    I am about to change a ceiling light fitting back the rose type but the mains cable coming through the ceiling (which is the only cable) is not showing live on my electric screwdriver tester? and yet the light-switch on the wall is definitely showing live? I don't understand what could have happened because the previous spot lamp fitting was working up until the bulbs gave out? Nobody has been in the loft to disturb any wiring... and besides it is boarded over.
     
  2. kevinbaldy

    kevinbaldy Member

    please do not use a electric screwdriver tester to confirm power to /or isolation of a circuit . they should not be trusted .
     
  3. BEF

    BEF New Member

    oh blimey! I never knew that I have used one for many many years! so why are they sold if they are not safe?
    Thanks
     
  4. kevinbaldy

    kevinbaldy Member

  5. terrymac

    terrymac Screwfix Select

    Is the existing light fitting extra low voltage ,run from a transformer ?
     
  6. BEF

    BEF New Member

    no transformer straight from mains
     

    Attached Files:

  7. terrymac

    terrymac Screwfix Select

    Have you connected the pendant to the terminal block to see if the bulb lights ?
    When the last fitting stopped working ,how do you know it was because of bulb failure ?
     
  8. BEF

    BEF New Member

    Not yet that will be my next step thanks. although I still don't get that my electric screwdriver tells me there is power at the switch but not at the ceiling?
     
  9. terrymac

    terrymac Screwfix Select

    Have you tested for voltage on both sides of the switch ?
     
  10. BEF

    BEF New Member

    Yes it only the red live showed voltage
     
  11. terrymac

    terrymac Screwfix Select

    With switch in " on" position ,both conductors should be live ,I.e the incoming to com terminal and the outgoing switched live at L1. Are you saying only one of them is live ? If so the switch is duff.
     
  12. BEF

    BEF New Member

    oh that would make sense then? and it is quite feasible as the light switch has had a very hard knock recently....
    I will check this out too thanks you for your help!
     
  13. terrymac

    terrymac Screwfix Select

    Do Let us know how you get on.
     
  14. FlyByNight

    FlyByNight Screwfix Select

    Also, you need to be earthed for it to work. Standing on a fibreglass or wooden ladder (or even a chair) will stop a neon screwdriver from working!

    At least you know the screwdriver works!
     
  15. BEF

    BEF New Member

    Hi, this is the first chance I have had to get back to this - please can you look at the wiring to the switch for me? I don't quite follow the this set-up the 3 black cables are capped together?
    I haven't yet connected the rose and pendant until I am sure.
     
  16. BEF

    BEF New Member

    oops forgot the pic...
     

    Attached Files:

  17. terrymac

    terrymac Screwfix Select

    It's too blurred to make out. Can you show the connections at the back of the switch plate ,and any in the enclosure ?
     
  18. BEF

    BEF New Member

    is this better?
     

    Attached Files:

  19. terrymac

    terrymac Screwfix Select

    Yes much better. The black insulated conductors are neutrals connected together ,all fine. The bare earth conductors should be sleeved in green/ yellow sheath. The switch plate is metal and the earth conductors should connect to its earth terminal on the back of the switch plate. The two red insulated conductors together in the " com" terminal are the live supply in ,and ongoing to the next switch. The red in a terminal ( probably marked L1) on its own is the switched live to the light fitting ,and should be live when switch is " on" ,and not live when switch is " off"
     
  20. BEF

    BEF New Member

    all makes perfect sense thank you - I am guessing the switch maybe upside down then would this be correct? because I get a neon when the switch is off and nothing when it is on...
     

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