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Old AC voltage out of some fittings

  • 14-07-2011 12:37pm
    #1
    case_sensitive
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭


    Hi all,

    I've got gremlins in my wiring.
    Since we moved into our new house (built around 1999) a few months ago, two of the 6 light fittings haven't worked, despite changing the bulbs etc.

    There are 3x GU10 downlighters in the living room (see working and faulty pics).

    There are also 3x pull chord fittings with globes.

    Each pair is controlled by a single switch at the front door, so with the leftmost switch, the pull-chord and downlighter nearest the door are activated, middle switch only controls middle downlighter, and right controls downlighter and the two pull chords by the farthest wall (I think, as 2 of these 3 don't work).

    The weird problem is the voltage, I could understand if nothing was coming out of the faulty ones, but it's not NO voltage, it's just an oddly low voltage.

    On the pull downs that do work, with the chord 'down' I read AC 229V across the terminals, grand. With it 'up', a nominal 0.5V

    On the misbehaving pull-down fitting, with the wall-switch closed (on) regardless of the state of the pull-chord, it reads AC 22V. Not 0.22, not 2, but 22V, I'd take a picture, but I'm all out of hands. With the wall-witch open (off), and the chord down, it reads 21V AC, and 0.4V with the chord up. !!!??

    On the misbehaving downlighter, it reads AC 18.4v with the switches on, a nominal 0.8V when they're off.

    My first reaction was that my multimeter was acting up, so I replaced the battery and tested against other AC sockets, and known DC sources, it read within norms.

    Another interesting factoid, that I noticed only after I replaced all the 50W halogens with 3W LEDs is that even when 'off' the GU10 sockets still allow a trickle charge through the circuit, throughout the house. The LEDs require so little power that they visibly light.
    There are 10 GU10s in total, and all but one have the 3W LEDs, and they're all lighting in the dark (see picture).

    Ever seen 22V AC before? Is there a rogue transformer somewhere in the ceiling/wall?


Comments

  • #2
    case_sensitive
    Registered Users, Registered Users 2 Posts: 853 ✭✭✭case_sensitive


    More pictures


  • #3
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    On lights with 2 way switching, voltages such as your getting can be seen when the lights are off, due to inductance between the 2 way strappers which would be usually run together, especially in a twin brown strappers setup.

    In your case it is likely not a 2 way switching setup, just switch on with wall switches and then pull chords can switch the wall lights on or off, but there is probably an open neutral, as a digital voltmeter will read voltages such as your getting, when a test is done from a live to an open circuit neutral. This would also mean the light wont work.

    The fact the led downlighters are lighting dimly means the wiring for the lights is in a bit of a mess.

    It actually almost sounds like the lighting wiring is in reverse polarity as well, because pulling the pull chord on the wall lights should of brought the 22v to near zero if the pull chord is in fact switching the live at the wall light and the other probe of the meter is on an open circuit neutral, which may account for all the led fittings slightly glowing with a constant live feed into them.


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