The intention was to mimic a typical small installation where there are existing GU10 filament lamps on a dimmer and where the client simply wants to swap them for LED versions.
This month we have taken some LED GU10 lamps and connected them to a range of rotary dimmers. We then dimmed the lamps to see how well they performed.
The Hamilton dimmed all the lamps smoothly and silently down to less than five percent. It even held the Verbatim steady at one percent. The only exception was the Supacell which would only dim to about 35 percent.
The MK gave smooth dimming down to less than 10 percent on all the lamps bar one. Most produced a slight hum. The Kosnic performed particularly well and was silent. The Supacell wasn’t really compatible; below about 50 percent, the flicker was too severe. Of course, MK also make dimmers suitable for LED GU10 but we wanted to test a retrofit situation.
The Enlite, GE, Kosnic and Verbatim all dimmed to below 20 percent. The Enlite and GE performed particularly well. The Supacell would only dim to 35 percent and it was noisier at all levels. The Verbatim did flicker slightly at some intermediate levels but this could be cured by adjusting the output up or down a small fraction.
We obtained popular LED GU10 lamps from five different manufacturers. The lamps were typically 5W – 6W and produced 400lm – 500lm. We then put four identical lamps on a mains track (so the load was 20W – 25W) and connected it to a range of wall-plate type dimmers.
It worked straight out the box and gave smooth operation with all lamps. It even managed to dim the Supacell to about 10 percent and other lamps were as low as 1 percent or 2 percent.
Dimming was smooth and silent down to less than five percent with all the lamps except the Supacell. The Supacell worked best with the V-Pro. We told Supacell of our results and they say that new versions of this lamp will have an improved NXP driver. This should reduce flicker and noise.
What can you do to obtain the best result?
Look for a dimmer with an adjustable ‘minimum brightness’ setting. Many dimmer manufacturers offer this option and it helps to avoid any instability at low level.
Make sure the LED load is above the minimum for the dimmer. Many dimmers have a minimum load, say, 20W. If you are connecting just a few low wattage LEDs, you need to exceed the minimum load required. If this isn’t possible, adding a resistive load can often help and many dimmer manufacturers offer one as an accessory.
Don’t overload the dimmer. This is unlikely if you are replacing filament GU10 lamps by their LED equivalent. However, if you are buying a new dimmer specifically for LEDs, you may find that it has one wattage rating for filament GU10 and a lower wattage rating when using LEDs. This may be 25 percent lower or an even smaller wattage.
The firmest conclusion is that if you have an existing ‘tungsten’ dimmer, you should change it for a dimmer specifically suited to LEDs.
The Doyle and Tratt, Hamilton and Lutron dimmers were designed for LEDs and produced much better results over the whole range of lamps. They were quieter and dimmed to lower levels.
We would like to thank the companies mentioned together with Danlers and Fab Controls for their assistance with this article.
You can find out more about dimmers at Lux Live, which will take place on the 23-24th of November 2016 at the Excel Centre in London. .