Dimming LED lamps

Craig Turner · Aug 23, 2014

Hi All,

I've just registered with the site after struggling to find a solution to my problem via google. I'm hoping some of you on here might be able to help me out as my experience with LED lamps is fairly limited due to working on the railway for the past 7 years and not doing much install work; my product knowledge is not what it once was!

Right, I have fitted 6 Osram parathorm advanced 7.5W GU10 style LED lamps in my mum's bedroom (down lights) and replaced the switch with a Varilight remote control dimmer. When I switched the power on the lights were behaving very strangely. When I operated the switch one lamp only lit up initially (very strange I thought since obviously they are all wired in parallel). When I held the switch down to dim/undim, all lamps came on but the light level kept subtly going up and down.

My initial response was to go through the instructions that came with the dimmer. I checked that the earth cable is correctly sleaved and that the live & switch line are connected the right way around as stated in the instructions. No issue here.

Next I contacted the manufacturer for advice as I suspected a compatibility issue despite the fact I have used the same lamps and dimmer (same models) in my own house. Varilight responded quickly and said I needed to order a different switch; the Varilight V-pro Eclique which is fully compatible with most good quality dimmable LED lamps. They also said that a maximum of 10 lamps can be connected and the total wattage must not exceed 100W. Apparently the fact that only 1 lamp initially illuminated on my set up is due to the electronics and the way LED lamps use the current (he did explain in a bit more detail but I can't remember the exact explanation).

Anyway, the LED lamps have been refitted and the new LED compatable switch fitted but I'm still getting the same issue, very frustrating! I'm thinking it could be either:

1) a faulty switch (although as I said I have the same lamps on one of the lesser non LED switches in my house and they work fine so I'm not convinced that both switched I've tried are faulty).
2) one of the lamps might be faulty.
3) an earth fault somewhere on the circuit. I say an earth fault as the mention the earth sleaving in the instructions so I assume that the earth must play some part in the correct operation of the switch.

Any ideas or comments would be much appreciated!

cheers.

dingledong · Aug 23, 2014

You need to buy dimmable led's

Craig Turner · Aug 23, 2014

dingledong said:
You need to buy dimmable led's

Thanks for the reply. They are dimmable, appologies for not making that clear in my original post.

sammyshooter · Aug 23, 2014

Are they dimable LEDs? You need a Leading Edge dimmer for them. You done an IR test on your cabling? You tried a normal 1G switch, or tried using halogens with that dimmer? Just double check the loads first. You often get conflict with control gear, so it may be compatibility, the LedLite range is great for getting around this.

Craig Turner · Aug 23, 2014

sammyshooter said:
Are they dimable LEDs? You need a Leading Edge dimmer for them. You done an IR test on your cabling? You tried a normal 1G switch, or tried using halogens with that dimmer? Just double check the loads first. You often get conflict with control gear, so it may be compatibility, the LedLite range is great for getting around this.

Hi sammyshooter. Yes they are dimmable and I've used the same lamps with the same dimmer in my house without any issues. The switch can operate as a leading edge or trailing edge dimmer but doesn't seem to work either way. With normal halogens fitted everything works fine. This leads me to suspect a wiring fault or maybe the electronics in one of the lamps could be faulty and causing problems? I haven't Insulation resistance tested yet as I don't have any test gear with me today (following my discussion with Varilight I was convinced the new switch would solve the issue so didn't come fully equipped!). Just about to try removing some of the lamps to see if any of them could be faulty.

HappyHippyDad · Aug 23, 2014

It does sound a bit odd Craig. You say you have exactly the same set up in your house.. same bulbs, same dimmer switch and they work fine. thats half the battle really with dimming LED's, finding a combination that works and sticking with it.

Why dont you take the dimmer to your house and see if it works as it should? Also just try some other dimmable LEDS's? Swop the bulbs around see if it really is just that one that works or if it the position that it likes?

Plus I believe that 'trailing' edge rather than 'leading' edge is more appropriate although like you say the varilight can operate in both modes (if you can figure the instructions out) and I believe they come pre-set in trailing edge mode http://www.electriciansforums.co.uk...railing-edge-leading-edge-led-downlights.html

Craig Turner · Aug 23, 2014

Yeah I was thinking that, I'll take it home and try it on my lights. As for the lamps I've tried swapping them around with a couple of spares I had and only running 1 or 2. I will consider trying another brand of lamp it's just a pain because of the cost. I've also tried disconnecting everything bar the 1st light to eliminate the other wiring. Still getting an issue. I can't even get the halogens to work off it now! Also I've noticed that the blue led ring (on the LED compatable switch) flickers when LED lamps are connected when the switch is off.

I've given up for today now, I've reinstated th halogens and the original non LED remote dimmer. I suppose it's possible that the new switch is faulty (this has happened to me before with one of the older Varilight switches) or that I've somehow damaged it with all the messing around. I still can't understand how I have both LED compatable and the old type non LED switches running these osram lamps in my house with no problems. The only thing I can think of doing now is full continuity and IR tests on the circuit including switch line.

I will contact Varilight again in the week with all the info and see if they have any theories. If it wasn't for my mum wanting the remote function I'd just fit an alternative brand of switch! It's my own fault for recommending LED lamps, I should have just gone with halogens!

thanks for clearing up the trailing edge/leading edge thing. I was a it unsure about that.

Thanks for all the replies so far.

london-electric · Aug 25, 2014

Hello Craig ,

We had exactly the same problem with exactly the same lamps on a job this week.
The varilight v - pro was doing some very strange things , we sent it back and the wholesaler sent us a bg dimmer module, one which has a adjustable setting on the back for min. brightness
They worked a treat , not sure if it's because those lamps don't actually require a trailing edge , but just a dimmer that can handle the led load ??

Give it a try

Hope this helps