Buzzer dimmers.?

[biggal5]

Hi, I've read a few threads about buzzing dimmers on here but still have a query and would like some advice please.;

Customer has x4 low voltage downlights with electronic transformers for halogen lamps fitted to each downlight. These transformers are 60VA each (Saxby model ET60T-R 20-60VA 4.9amp max selv) and a dimmer switch is fitted. Problem is that the dimmer has a very noticable buzzing sound, not so much when full on but when dimmed it is very noticable.

I have changed the dimmer 3 times already, 1 was a 250w rating, then a 400w and last I even put on a 1000w to see if that would help but still very noticable buzzing. I also have changed the lamps from a 50w GU5.3 to 28w lamps to reduce the load but no difference either?

For working out the load is it correct to take the transformer rating at 60VA and if so 4 downlights should still be well in range of a 400w dimmer? even after a 20% de-rating.

Also, before I left I put on a 250w trailing edge dimmer and there seemed to be a reduction in the buzzing however the lamps flickered a lot. I have read somewhere that for electronic transformers to work they need to be loaded to a minimum of 70% of their rating when being dimmed? Am I wise to put back in the 50w lamps and use trailing edge dimmer in that case?

Also, the original dimmer could have been poor quality however the last one I bought where £25+ each so not bottom market. It is also fed by a 6amp type breaker.
Any advice and help would be appreciated please.

 

[telectrix]

i'd be inclined to rip out the transformers and fit GU10 dimmable LEDs. the less electronics you have, the better.

 

[acvc]

You must have had a really deep backbox for the 1000W dimmer, or is it surface mounted?

 

[biggal5]

had a 35mm backbox in place. .. Regarding taking them out they have 4 rooms with 4 downlights in each fed through a dimmer. These are supplied by 2 separate 6amp mcbs. Taking out 16 lights is too much hassle for them (and I would like to find a solution for future reference!)

Also at one stage when switch was dimmed there was a buzzing at the CU.? Is this a sign of overloading at the breaker? and if so am I best to change to 10amp (run in 1.5mm with short cable runs)

 

[nuelec]

Telectrix, Did you get anywhere with this problem?
I have the same issue with the same transformers. I am putting it down to poor quality transformers. Installing spot lights & dimming them is bread & butter work. Have been doing this for years with no problems. We have installed about 20 of them in various rooms on a job. Lights were specified by architect so had no reason to question the quality. All dimmers buzzing & lights flickering & customer is not happy! tried several dimmers. even saxbys own but problem not fixed. Now looks like i am going to have to replace them all at my own expense. I am following this up with saxby to see what they say.
If you have managed to resolve your issue please share. Thanks