leading edge dimmers?

[Marbles]

I was asked to look at a job locally where the bloke had 8 x 50 watt gu10 downlights in a kitchen on a 400 watt dimmer switch. He said the dimmer had stopped working but he was having to change lamps quite frequently. I said that the dimmer was on its max load and he would be better down rating the lamps to 35 watt to help it out, and I stripped circuit and tested continuity through circuit as he wanted to know the circuit wasn't causing his lamps to go via any high resistance joints. Having replaced the dimmer with an equivalent from a reputable online lighting company and changed the lamps for 35 watt ,within two weeks two lamps have gone and the dimmer has stopped working! Would a leading edge dimmer be a solution to this problem or trailing edge, I havn't really any experience with the technicalities of dimmers so any advice appreciated?

 

[telectrix]

you need a 700watt dimmer for that lot. always take the load and x 1.8. for halogens ans dimmers.

 

[Marbles]

would i get away with a 500 watt dimmer or is that cutting it fine?

 

[Marbles]

I read that when gu10 lamps blow they can cause a short circuit enough to blow the dimmer? Would a trailing edge or leading edge dimmer be protected from this?

 

[telectrix]

solution is to fit a 700 watt dimmer with an in line 3A fuse. probably need a deeper back box. you might get away with a 500w, if the halogens are 35w, but then customer will fit 50's anyway when replacing.

 

[Midwest]

Soft start dimmer's I believe can help. http://www.varilight.co.uk/leaflets/compatibility.pdf

 

[amlu]

talk the client into changing them for leds... they will pay off in maintenance costs and leccy bills over time.

 

[Marbles]

Has anyone any experience with these new dimmable leds? are they any good the early ones weren't good?

 

[BlueToBits]

Trailing edge puts less stress on the lamps as the current is always triggered at the 0v crossing point of each cycle. A fuse in the switch will never be fast enough to protect the dimmer in a short circuit situation. The dimmers get stressed because the cold resistance of TH filament is very low and they therefore have a high switch on surge. Modern dimmers are supposed to be able to cope with this. You could try taking out the triac and replacing it with one of a higher current but similar trigger ratings.

 

[Midwest]

Has anyone any experience with these new dimmable leds? are they any good the early ones weren't good?

Been quite a few threads about led dimmers. Iv'e used the Varilight ones in my own house. They can dim down to about 30-40%.