[Spy]

I have recently installed Rako in-ceiling dimmer packs and they buzz

I thought buzzing was only on cheap rotary dimmers.

Do others have the same problem with Rako dimmers ?

[Johnny Thunder]

Are you dimming low voltage lighting?
Which model have you installed?
If it is low voltage, which transformers are you dimming?

[Spy]

Hi Johnny,

Yes, I am dimming low voltage lights 12V-50W. Each light has its own 105Va leading edge transformer.

The dimmer packs are RDL500C - in-ceiling 500W dimmers. They are powering different numbers of lights from 6 to 9. Whether a dimmer pack is powering 6x 50W lights or 9x 50W lights it still buzzes !

[Johnny Thunder]

Have you got a link to the transformers Spy.

[Spy]

I'm afraid not, but I had a quick look at one and it is called:
TCI Saronno VX.60.
It states it is dimmable by a leading or trailing edge dimmer.
Min 20W, Max 60W bulb

[Pop up Dragon]

I think if you are running 9 x 50watts that very close to the limit of the RDL500.I pushed mine to 450 and they got a bit warm,but stayed silent.Have you checked to see if its the dimming module or the transformer.I have one cct in the living room that over the last year controlled halogens(12v/240v) and ordinary bulbs of several wattages and its alway silent.

[Spy]

Hi Dragon,

If all the dimmer packs were controlling 9 bulbs then I might think it was because I was pushing it the limit.

But I have two other 500W dimmer packs controlling 6 lights each and they also buzz !

I am notr sure of the sigificance of the transformers but it is definitely the dimmer packs that are buzzing, the transformers are silent.

[Johnny Thunder]

Spy, are they running hot?
Is there insulation in the ceiling void?

[Spy]

I haven't checked to see if they are running hot, but there is no insulation in the ceiling cavity, it has been suspended below the original ceiling.

[TTT]

The usual cause of buzzing is low quality transformers. I am not familiar with the ones that you are using, but have a chat with the dealer who sold them to you- Rako have a list of "recommended" parts that give consistently good results.

[rssteve]

just to add to this, although your lamps(bulbs) are only 50w, the transformer is going to draw more current than that, each transformer may draw 60w etc. just a thought.

[Rack]

It's not the quality of the transformers necessarily. There can just be a bad combination of dimmer and transformer, neither of which are neccesarily 'bad' on their own.

It is always best to use a trailing edge (aka reverse phase) dimmer with an ELV transformer. I don't think Rako have one, so not much help there. Replacing the transformers might help, if they have a recommended list, would be worth a try. Or if you are looking to replace it, try and find a trailing edge dimmer for your lights.

With 450W of ELV on a 500W dimmer, I would watch out, irrelevant of the buzzing. I've had a 500W rako dimmer switch off with 400W of ELV's on a hot day - it just switched back on again when it cools down, but not ideal.

[Johnny Thunder]

Rako dimmers are Leading Edge, not trailing.

[Rack]

Originally Posted by Rack

I don't think Rako have one, so not much help there.

Originally Posted by Johnny Thunder

Rako dimmers are Leading Edge, not trailing

Hmmm... Lutron Rania and GXI-3xxx have ability to run leading or trailing, but seem to be only ones on the market for that size installation.

Not really replacements for the Rako dimmer though. Maybe try some different transformers, but all transformers have a very similar looking input so there's no guarantee. Can you ring them and see if they have a recommended transformer that runs well?
I know Mode do some very nice transformers, but they are expensive.