How to dim an 8W LED load?

11 Mar 2011
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United Kingdom

I've got two dimmable 4W LED bulbs in downlighters (in series). I bought this dimmer:
because TLC advertised it as having a minimum load of 3W. I fitted it and the dimming is almost non-existent, maybe 5% or so. Now going back to the manufacturers spec on the box I see they state a minimum load of 10W, so no wonder it won't do much with an 8W load.

If I replace one of the 4W LEDs with a dimmable 6W LED bulb, to make the load up 10W, do you think it would then dim with this switch?

Seems odd adding watts to get a dimmer light, but I don't fully understand how these trailing edge dimmers work. If not, does anyone have any other ideas for dimming an 8W load?

Thanks, Chris
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It depends on EXACTLY what the load is.

To dim LED elements ( the bit that produces the light ) is simple. All that is needed is something to control the DC current flowing through the diode.

But most LED lamps are one or more LED elements together with a built in controller ( driver ) that converts 230 volts AC to a DC current or a 12 volt supply to a DC current so the simple means of controlling the current to dim the LED is not accessible. Some drivers will detect that the mains supply is "dimmed" and change the current through their LEDs to match. Many don't.

Also the dimmers that replace switches have to work without a neutral and as a result of that need a minimum load current to enable the electronics to have enough power to work.
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Yes, well spotted, I think I must have got the wrong product code because on the manufacturers box it clearly says 'dimmable':

Phillips MASTER LEDspot MV Dimmable

4W GU10 3000K 220-240Vac 40D
50-60Hz 29mA
If you have really connected them in series then it is not going to work?

Also if you read the info on the Phillips website about dimming you find out that you have the wrong dimmer.

Quote From Phillips
Currently, Philips LED lamps work best with R & RL type dimmers, while installation with RC & RLC type dimmers is not recommended. Common phenomena when connecting LED lamps with the wrong type of dimmer are:

-Flickering of the light in certain dimmer positions
-Audible noise emitted from the dimmer unit
-Light level is not dim enough even in lowest dimmer position

Note: R & RL type dimmers are "Leading Edge"
Yes, sorry, another mistake, they are not connected in series. Thanks also, it looks like the key page on the Philips website doesn't work but I'll email them.

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