Dimmer – Strange behaviour

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This topic contains 2 replies, has 2 voices, and was last updated by  lennyg 2 weeks, 5 days ago.

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  • #23615
     lennyg says:

    lennyg
    Participant

    We are going through a major refurb at the moment and decided to get a couple of 4 gang dimmers for the kitchen circuits. The electricians for one reason or another have wired the lighting circuits so that the live and neutral are at the switch with just a switch wire going to the various lamps.

    Our issue is that when there are no lamps in the holders (we’ve tried various flavours of GU10′s) there is a live feed to all the lamps, however when we plug a lamp into one of the sockets there is no power to the lamp i.e. using a voltage wand it indicates 240v with no lamps in the holders and 0v as soon as you plug a lamp in, though the amber light does come on when a lamp is plugged in.

    Any guidance appreciated.

    #23648
     Bruthal says:

    Bruthal
    Participant

    The dimmers use the lamp as part of the circuit, with a very small current through the lamp to operate the dimmer, so eliminating the need for a neutral to the dimmer itself. With the dimmer having a very high impedance in the off state, all the 230v is across the dimmer.

    When you remove the lamp, the 230v is now across the open circuit at the bulb, so you detect this with high impedance testers such as a voltage wand. Bulb in, and it is like connecting the neutral pin to the live one via the bulb filament, because of the impedance of the off state dimmer being far higher than the bulb filament.

    Is the dimmer working as it should?

    #23652
     lennyg says:

    lennyg
    Participant

    Thanks for your response. 3 out of the 4 circuits for this dimmer have been 2nd fixed, we’ve found out today that the electrician had connected master 4, 3 & 2 in that order without actually making the last (master 1) circuit. By changing this around so that the first live in was to master 1and not including the final, unmade, 2nd fix circuit the dimmer has now started working. One thing we have noticed though is a very faint glow from the LED’s in their off state. Is that a byproduct of the small current required to operate the dimmer.

    Thanks

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