Changing light fixture - How do I confirm the power is off using a multimeter?

Discussion in 'Electricians' Talk' started by Kramer85, Jan 21, 2022.

  1. Kramer85

    Kramer85 New Member

    I'm planning on changing the light fixtures in my ceilings to LED ones. The ceiling rose looks quite simple (nothing in the loop, just single Live, Earth, and Neutral wires).
    Once I've turned the power off, how do I use a multimeter to confirm there is no power in the wires?
    Where do I connect each prod?
    There's not much in the manual, but I'm thinking I set the multimeter dial to V~(AC) 600v. Where do I put the red and black prods to verify there's no power in the light mains? I've looked online for video demos, but no luck.
    Pictures attached.

    Attached Files:

  2. CraigMcK

    CraigMcK Screwfix Select

    I’m not convinced you should do it if you are not sure how to measure the voltage. I would ask though, that fitting looks like it’s either a flush mount to the ceiling or actually in the ceiling itself. What are you planning to do with the rose?

    Also I hope you like a bright room 24W is a lot!
  3. Ind spark

    Ind spark Screwfix Select

    With the power on, test between blue and brown then brown and earth.

    You should get 230 to 240 volts.

    Then switch the circuit off and do the same, you should get zero volts.
    Last edited: Jan 21, 2022
  4. The Happy Builder

    The Happy Builder Screwfix Select

    If in doubt turn the whole house off at the big red switch and any solar panels main switch if there is one.
    BiancoTheGiraffe likes this.
  5. Kramer85

    Kramer85 New Member

    I'm planning to disconnect the pendant currently connected, then remove the rose.
    I'll install the new mounting bracket into the ceiling, then connect the Live and Neutral wires to the new LED light via wago connectors, and also connect the Earth to wago connector (there's no Earth input on the new light, it's double insulated).
    That sound good?

    To be honest I never use the big light. I just hate the pendant/lampshade hanging down from the (not particularly high) ceiling.
    I'll dim the LEDs as much as possible, but it'll never really be used anyway - I just didn't want to replace it with nothing.
  6. Kramer85

    Kramer85 New Member

    Which prods go to which wires though? Does it matter?
    Also, where do I actually put the prod ends? Just against the screws in each wire?
  7. Kramer85

    Kramer85 New Member

    Yeah was going to that anyway, but a lot of the guides I've read/watched tell you to check that there's definitely now power in the light mains even after you've turned all the power off. I just don't know how to check this exactly.
  8. terrymac

    terrymac Screwfix Select

    Doesn't matter which probe goes to each conductor. Red probe to brown wire ,black probe to blue wire would give exactly the same voltage reading if the probes were the other way about ,for instance ,when taking AC voltage readings.
  9. Kramer85

    Kramer85 New Member

    Great, thank you. For testing, do the probes just need to touch the screws that hold each wire in place?
  10. BiancoTheGiraffe

    BiancoTheGiraffe Screwfix Select

    Yes, that's correct
  11. Kramer85

    Kramer85 New Member

    Thanks for confirming.
  12. terrymac

    terrymac Screwfix Select

    As long as the screw is tightened against the copper conductor ,that's ok
    But it's the copper conductor that you are testing ,to be pedantic.
  13. The Happy Builder

    The Happy Builder Screwfix Select

    Test the fitting whilst it is live to check it and the tester.

    Turn the power off then check the fitting is dead.

    Really you should then test the tester somewhere else to check it is the power that has gone off and the tester hasn’t packed up.

    Be careful to get the right setting on the tester or else it may go bang.
    terrymac likes this.
  14. Kramer85

    Kramer85 New Member

    Such as what?

    It should be V~: 600v, right?
  15. Ind spark

    Ind spark Screwfix Select

    Proving unit or pop next door;)
  16. Kramer85

    Kramer85 New Member

    Okay, but I'm putting the prong in here, right?:
  17. Ind spark

    Ind spark Screwfix Select

  18. The Happy Builder

    The Happy Builder Screwfix Select

    As a rule if thumb if the light is still on, so is the power :)

    But you can get caught out, but that’s unlikely with wiring as simple as this.
  19. Bazza-spark

    Bazza-spark Screwfix Select

    Or simply test and prove live,

    Swich off, test and prove dead,

    Switch back on, test and prove live,

    Switch off, test and prove dead. Carry out change of fitting.

    Switch on and show off to her saying "See, easy!".

    or come back here with before and after photos asking what you did wrong.
    Comlec likes this.
  20. Tony Goddard

    Tony Goddard Screwfix Select

    I'm with happy, do it in the daytime, throw main switch and crack on - don't much like basic multi meters, numbers jumping all over the show picking up induced voltages etc. in the absence of a decent tester turn off the whole show.
    BiancoTheGiraffe likes this.

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