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Lights not dimming?

Discussion in 'Electrics UK' started by zenonithus, 16 Feb 2021.

  1. zenonithus

    zenonithus

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    Hey all, just bought 4 pricey LED GU10 dimmable bulbs. Installed them in the kitchen light and whilst they are nice and bright they aren't dimming. Could this be an issue with the dimmer switch? Possibly not being compatible with LED? Or the actual spotlight bar itself? Here are the specs for the bar. Doesn't mention LED. Does this mean it's Halogen only?

    • W80, D10cm.
    • Diameter 23.5cm.
    • 18cm drop.
    • IP rating 20.
    • Requires wiring.
    • Bulbs required 4 x GU10 eco halogen (not included).
    • Recommended maximum wattage: 50 watts.
    • Manufacturer's 1 year guarantee.
    • EAN: 9274349.
     
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  3. bernardgreen

    bernardgreen

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    The spot light bar will almost certainly be able to take LED or Halogen lamps.

    The most likely cause of no dimming is that the dimmer switch dims in a way that the new LED lamps do not recognise.

    Did the lights work and dim when Halogens were fitted ?,
     
  4. Harry Bloomfield

    Harry Bloomfield

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    If you replace one LED, with one halogen, does the halogen then dim?
     
  5. zenonithus

    zenonithus

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    I think when I bought it the bulbs were included (not sure which type) and dimmed fine. Then I replaced with halogen and they didn't dim. So do you suspect the actual switch? Are there some older switches that are not led compatible? That would explain it.
     
  6. ericmark

    ericmark

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    Dimming switches come in different flavours, one is the range, often 40 - 200 watt or similar and if the LED total is too small they will not work, there is also leading and lagging, there are three ways to dim lights, variable resistor, variable transformer and wave form chopping, the first two need a large space and unlikely to be found in the home, and the latter can chop leading or lagging half of the wave form, with switch mode power supplies used for 12 volt lights leading or lagging matters as in real terms it tells the electronics in the switch mode power supply (electronic transformer) what to do, where the current regulator in a LED bulb is switch mode it may also matter, but in the main cheap dimmable LED lights use a simple capacitor to regulate current so it does not matter.

    The most likely problem is the dimming switch is not designed to go that low in output.

    Dimming switches need power, there are two methods to get power, one line to neutral, the other line in to line out, it drops the output just a small amount and uses that power to work the switch, so they can work without a neutral, however the electronics used can interfere with the lights, tungsten lights have a coil in them, so some inductance, and LED lamps a capacitor, but can interfere with the electronics of the lights, causing them to flicker, with LED some bulbs have a smoothing capacitor which stops the flicker, and some also have a resistor to leak away a little power so when an electronic switch turns off, or a two way switching has some capacitive leaking in the wires, the bulbs will not flash when switched off, so flicker and flashing can be a problem with some bulbs.

    EU rules said any bulb which can't be dimmed must be marked Not-for-dimmer-switch.jpg however it does not say they must say how they can be dimmed and the variable resistor or variable transformer may be able to dim the bulb but it can't be dimmed by wave chopping but it seems they don't need to tell you, the same with resistor to stop flashing when off, and the smoothing capacitor to stop the flicker, so it is a case of suck it and see.

    Both the smaller of these bulbs says suitable for dimmer switch G9-small.jpg G9-big.jpg the larger does not even give wattage or lumen output so breaks the EU rules, however the small bulb flashes when off with electronic switches and requires an external load capacitor and flickers when on, the large bulb works A1, the problem is with G9 lamps the old quartz required glass covers to catch the red hot bits should the bulb blow, and these covers will not fit on large bulb, so it changes the whole look of the chandelier they are fitted into.

    But electronic switches be it simple remote controlled on/off or dimmers if not neutral used are a problem with some bulbs, the old BA22d, and E27 and even E14 don't seem to have a problem, but GU10 and G9 do.

    In warm countries where LED or CFL saves energy, they used a different method, they would split lights into 1/3 and 2/3 on switches giving three levels of lighting, as they used CFL first which would not dim, their rooms were hot enough as it was without tungsten bulbs, so they moved to light only bulbs well before us, in this country likely the tungsten bulb saves energy, as it allows the air temperature of the room to be lower, due to the inferred heat from bulb, and since bulbs only used at night when the room was in use, it gave a natural evening boost to only rooms being used. However since gas and oil costs less than electric the CFL and LED did save money, but not energy.

    Also quartz bulbs should not be dimmed, it reduces their life, as the quartz stays too cool and the tungsten adherers to the quartz instead of returning to the tungsten filament. Yes I know we did dim them, but we were not recommended to dim them, so any lamp designed to use quartz does not really need to be designed to dim, but using a dimmer as a soft start is different of course, and soft starts did seem to extend bulb life.

    We do use wall lights, standard lamps, and table lamps in this country to adjust room lighting, there was at one time a circular fluorescent with two tubes where you could select output, but the standard chandelier does not seem to be designed for the 1/3 and 2/3 split, and if you turn 1/3 off it simply looks as if some bulbs have blown. In the same way as a fan built into a light can use a remote control to turn it on/off we could design a chandelier to do the same, but it seems we have gone for the dimmer switch.

    What we need is for the Not-for-dimmer-switch.jpg sign to mean leak off fitted and output smoothed suitable for an electronic switch as well as being dimmable, but that is not the case at the moment, and now we have left EU we could do it, but would not hold your breath.
     
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  8. oldbutnotdead

    oldbutnotdead

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    If your dimmer worked with halogens and not with LEDs then its probably a cheap old triac dimmer. Have a look at the specs for the LED lamps, see what type of dimming they want.
     
  9. ericmark

    ericmark

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    That would be good, new lamp example 22019274 G9-69SMD-5730 AC:220-240V White written on the box, nothing written on the bulb, Other bulbs do have MiniSun M30 90G 240 V 50 Hz 3 W 300 lm 3000K and sign for dimmable. And yes hunt for MiniSun on internet does find adverts for nearly same bulb, however advert says not dimmable but bulb shows sign to say dim-able.

    This is the whole problem with LED lamps, go to for example screwfix website, look as GU10 bulbs, there is nothing to say leading, lagging, smoothed, with or without leak resistor all you get is Dimmable or non Dimmable.

    You can work a little out from 22019274 G9-69SMD-5730 AC:220-240V it has 69 surface mounted 5730 diodes which are 150 mA @ 2.8-3.4 Volts so between 30 and 35 watt, well that's not right, some where between 4 and 12 watt is more like it. At 45 to 50 lumen so 3100 to 3450 lumen one starts to wonder if some one got the decimal point wrong? 3.5 watt at 310 lumen seems about right for a G9 bulb.

    We know an LED lamp may use a capacitor or a pulse width modulated chip to control current, and with a PWM there is often a massive voltage range, so LED 10 - 30 volt will have PWM and LED 220-240 volt likely a simple capacitor, but as to specs, forget it, so upload_2021-2-17_15-16-17.png is dimmable and upload_2021-2-17_15-16-39.png is non dimmable and that is about as much as you can hope for.
     
  10. zenonithus

    zenonithus

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    Thanks for the replies guys. ericmark, some great info there, thansk for taking the time to explain how this all works. I'm still processing it all though good to get a knowhow on these things :) So is there a certain type of dimmer switch I should try that would likely be compatible with LED bulbs? Or any dimmer that mentions it's for LED should be fine?
     
  11. zenonithus

    zenonithus

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    oldbutnotdead: good point! I saved one of the boxes so will try to post an image or info on here if I can dig it out :)
     
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