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Dimmers - aargh!

Former Community Member
Former Community Member
Hi forum. Hope you are all well and enjoying the lovely weather and not working too hard. :)

I have a customer who's new kitchen/extension I wired in September. Since then they have been having one of the three lighting circuits in the kitchen flicker.

Allow me to describe:

House is on TT but in a suburban setting. Which is weird, but there you go. Zs is 2 ohms. I presume because of water pipes.

Anyway. One new circuit from CU on a 6A RCBO runs the new kitchen and outside lights. 3 gang dimmer switch runs: circuit #1 6 downlights, circuit #2 two pendants and a cupboard luminair (on a dimmable xformer), and circuit #3 another 6 downlights. The pendants are on a 2-way circuit controlled from a switch at the entrance way. There is additionally a pair of up-down lighters on a switch and a PIR flood on a switch.

Semi-randomly, and ONLY on the pendant circuit, the pendant lights flicker. As in, change brightness. Looks like interference from a car charger (though there is not one on the property). It's NOT 'I turned the LED down low and the triac is struggling' sort of flicker. It's only on the pendant lights. Pendants measure out 0.5 ohm r1 and 0.35 ohm rn bulb holder to CU.

I tried a Varilight Pro dimmer, and a Knighstbridge dimmer, both trailing edge types. I tried 2 different brands of bulbs.

I have bypassed the dimmer and that solves the problem - though of course they have now a non-dimmable light.

Before I give up and fit a push-switch where the middle dimmer used to be, anyone got any ideas?

Many thanks.
  • A very long shot - how high is the mains voltage, and how hot do the flickery lights run ?

    I have had problems with OSRAM branded LED dimmable bulbs that dimmed beautifully, for about 15 mins, and then came over all psychodelic. Messing with freezer spray and hair dryers shows the effect to be thermal -and for supposedly high efficiency lamps they run dashed hot, I reckon over 50C at the lamp base.

    Taking a stab that they might run cooler and be better on 220V than 240 I have been running one with 470 ohms in series (large wirewound and in a box by the rose) and order and peace has been restored, with not a flicker in sight. When I have enough data I shall be writing to OSRAM, but for now it is experimental.


    Why do you suspect a car charger ? I presume you have a good reason, but it is not obvious from your post what that reason is.

    Regards Mike.
  • Did you try changing the config in the Varilight Pro dimmer? They offer quite a few adjustments and seem to work with most dimmable led lamps. 


    Regards,


    Alan.
  • I have found Varilight to be very helpful through their contact link on their web page. Had an issue recently whereby a pulsing effect with some dimmable LED strip I had installed. It turned out that the driver unit was a toroidal type which required a 'non-standard type' of dimmer switch which I duly ordered and fitted which made the problem go away. Check the type of any LED driver unit you have in the circuit and ensure that the type of dimmer switch is compatible with it.

    (with belated thanks to MikePJ for his input on that one!)
  • No help with your problem but i advise all of my customers not to dim LED.  If they want them i offer absolutely no guarantee on the lamps or the switch so be it on their head.  I got totally fed up with call backs for them.



    Gary