Strange buzzing from db and dimmer switch module??? puzzling!!

[mitchy]

Hi all
im a qualified electrician with 6-7 years of experience under my belt and ive come across this problem which is driving me nuts and i hope someone might of come across the same thing as im loosing ideas??

I have a client who has got some downlights in the basement with 8*gu10 low energy 11w dimmable megaman lamps, i have put a richmond 500w grid dimmer module on these which i know is suitable as i have used the same dimmer on these lights before with no problem,

When i turn the lights on i leave the dimmer up full until the lights warm up but can hear a slight buzzing at the switch (last time i used this set up it ran very silent), once warmed up i dim these lights down and the buzzing moves from the switch to the mcb in the consumer unit (which is in the same room about 4 and a half meters away)

This circuit was protected by a 6a b type hager mcb and only has these 8 megaman and 5 other low voltage lights on the stair well leading to the basement so no chance of overloading!
even so i thought it may be a possible problem with the mcb so replaced it for a 10a b type still with the same problem!

I then thought possible loose connection (feed is at the switch - 2gang single 45mm deep box for stairs and basement) took the switch off and checked all connections, then checked all connections at the CU powered back up and still the problem was there!!

I then thought the problem might be a faulty dimmer so got a spare from the wholesale and tried it.... still the same problem!!!

The only thing i have used different from the last job where i used the same set up is a b type mcb instead of a c type which i will try just to tick it off the list,

does anyone have any other ideas what i should try?? after the c type mcb im out of ideas!! any suggestions would be welcome...............

 

[Deleted member 9648]

Welcome to the forum....absolutely no idea what could be causing that....another option to try is a cartridge fuse,I believe hager do a C/F carrier which fits their mcb boards.

 

[cagedanimal2010]

very strange! im stumped!

danny

 

[mitchy]

im glad its not just me!! im hoping there is not a loose (hidden) connection between the cu and light switch, the megger test, R1+R2 and Zs all read fine to the switch so no evidence of it, i know the cartridge fuse holder your suggesting will try that after the c type thanks for input, ......strange one isn't it!!

 

[mitchy]

do you think as it is such a short run to the dimmer from the cu i could be getting some kind of feed back down the supply cable? ive never heard of it before but this is what it seems like???, he has other dimmers on separate lighting circuits which work perfect.............

 

[GrannySmiff]

Odd we had a guy with a similar problem using dimmers and he had a buzz at the CU have a search maybe he had a solution.

Here it is, maybe you could ask him if he solved the mystery.

http://www.electriciansforums.net/e...-electrical-forum/26934-dimmer-buzzing-2.html

 

[nickblake]

With dimmers it is possible to get a buzz and its not a problem ,normally its cause by increased current due to the dimmer reducing the voltage ,this in turn causes a vibration of the choke (coil of copper wire in the dimmer) thus the noise this can be transfered to the MCB very likley if there is alot of lamps, to reduce this at the MCB try increasing the current of it to 10 amps C type, it is a very common problem in the theaters with dimmers , and can cause noise on sound systems too

 

[smartspark]

Yep an upgrade of dimmer looks like the culprit, get this from normal light dimmers when supplying low voltage lamps, makes a right racket if your trying to watch tv.

 

[Poshspark]

I had this problem when I changed a switch for a dimmer.
Either
Change dimmer for ordinary switch or change lamps for standard filament lamps.
Try this and I bet your buzzing will disappear.

 

[ringer]

Agree with Poshspark here - change the lamp type to confirm it is the type of lamp and not a fault on the circuit. You could also try contacting the lamp manufacturer's technical dept. Perhaps this combination of lamp type / dimmer type / mcb / distances / quantity of lamps just will not work without buzzing. I know you want to solve this, but don't knock yourself out trying to fix something that might just not be fixable.