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Buzzing GU10 LEDs Regardless of Brightness Setting?

Postby BritishBeef » Thu Jul 23, 2015 10:23 pm

Hi all.

We've just had our kitchen relocated and have 2 banks of 9 GU10 Lap Dimmable 5W bulbs from Screwfix in our new downlighters. I already have a set of these bulbs in our old kitchen and have been impressed with their output.

The new kitchen has these leds
controlled by a Varilight V-Pro Trailing Edge 3 gang dimmer switch. 2 gangs each control 9 leds and the 3rd gang controls a standard lightbulb.

The issue I have is that all the leds are buzzing whatever the brightness setting. It's not really loud but it's loud enough to be annoying. There is no flickering. Also, I don't believe they are getting up to full brightness - I'm sure the ones in our kitchen are brighter ( they aren't on a dimmer).

I cannot stand the buzzing and I was under the impression that an LED compatible trailing edge dimmer switch would ensure there was no buzzing. The dimmer switch cost a lot of money too :(

Any idea what is causing the buzzing?

Many thanks for your time and help.

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Postby ericmark » Fri Jul 24, 2015 8:49 am

There is nothing that should produce sound in a light fitting, however some transformers are not epoxy filled and some times other parts within the driver vibrate or within the dimming switch.

The dimming switch sends a signal to the lamp to tell it to reduce current it does not as with the old tungsten bulb reduce the power sent to the bulb.

As a result the bulb and dimmer unit must match. Although leading or lagging clipping of the wave form is normally recognised by the bulb there can still be a miss match. So LAP dimmer should be used with LAP bulbs.

The GU10 bulb has a driver built into the bulb which if it does not get a signal will drive the bulb to maximum output with a voltage range often from 150 volt to 250 volt this is one of the main advantages of using LED lighting voltage dips don't affect the bulb.

In most countries they don't use dimming switches, but instead use a 1/3 and 2/3 split on the switch, which gives three levels of lighting. So getting lamps which will dim means paying a premium price.

I will guess the dimmer unit and bulb don't match and so the frequency has dropped into hearing range. Since you already have three circuits personally I would do away with light dimming. Not really required for a kitchen anyway. But if you really want them to dim correctly then same make lamp and dimmer switch is the way to go.
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