Dimmer help please

Hello all,
So I'm in London, and new to the forum. I'm actually a web/networks person for an investment bank during the day, and have just started playing with C-Bus, purely for use at home. I've completed the 'Introduction to C-Bus' course (run by the UK Distributor of C-Bus), and am using a UK electrician for the mains wiring.

I've put together a design to cover the 3 floors of our house, and the plan is to 'C-Bus' rooms as they're renovated. The design is fairly simple (lights only at present), with a mixture of 12 channel relays & 8 channel dimmers in enclosures on each floor. I'm using the ethernet interface module.

Having now started to put it all together, I've stumbled accross what appears to be the best kept secret (at least in the UK!), and that's transformer compatibility with the 8 channel dimmer. It wasn't covered on the course, and I only stumbled accross it when reading the instructions which came with the dimmer.

I have 2 rooms each with 6x 12v 35w halogen downlighters, and am now unsure whether that's going to be a problem. The transformers don't have any useful (capacitance) information on them, and they're not a make listed in the dimmer docs.

So.....is it a case of they either will or won't work, or is there potential to damage the dimmer if I connect the circuit?

Any help appreciated.
Many thanks,
David.

 

Hi Ashleigh,

They're:

Enlite
EN-SC60
20-60w

Can't tell you any more than that I'm afraid.
Thanks,
David.

 

Dont forget that there is a 1A rating on the 8 channel dimmer which pretty much limits you to 4 50W downlights on one channel. The 6 that you are proposing are OK at 35W, but what happens when the are changed and someone decides to put in 50W thinking they want more light? THis will overload your dimmer. - Just a thought

Mick

 

Hi Mick,
Hopefully have that one covered as all the dimmer channels have a 1A MCB between the output & load.
Cheers,
David.

 

Be careful

Be careful, while a 1A output MCB isn't a bad idea (and maybe in fact required by your regs (its not in australia)) it won't give you the protection from this mild overload.

Consider

6 x 50W halogen downlights = 300 W (this doesn't take into account any transformer losses)

I =P/V

I= 300W/230V

Current = 1.3A

This wont trip a standard 1A MCB as a 'C' curve breaker has and instant trip rating of approx 7.5 time the rated current so you would need more than 7.5 A to flow for the breaker to instantly cut off...

A better approach would be to divide the 6 lights across 2 channels of three lights that simply come on together. The other alternative would be to use the 2A dimmer module.

 

Transformers and Dimmers

Better still why don'y you use the 4 channel universal C-Bus dimmer which features 4 phase independant channels and can use used with inductive or capacitive loads (ie magnetic or electronic transformers) L5504D2U and L5504D2UP.

 

Sorry - never heard of them. From a bit of research on Google, Enlite seem to be a cheapy brand in teh UK, so teh tramsformers will probably be some cheapy chinese rubbish. HOWEVER, in Europe you have a slight advantage, so you might be lucky...

Look for a symbol on the transformers - it will be a rectangle with a sloping "hill" (which indicates the ramping of light level)... and under the ramp is the letter L and/or C....

This Enlite one (ebay UK) doesn't have the marking :
http://i13.ebayimg.com/06/i/000/8d/4f/78e1_1_b.JPG

But these other images do have the marking :

http://www.tridonicatco.com/kms/media/images/viper_copy1.jpg
(left side, below the V)

http://www.pferdekaemper-shop.de/images/530747.jpg
(Middle - 2 symbols left of the CE mark)

Here's a Osram newsletter that shows it really clearly and explains the way the Europeans are doing things to make it easier to determine compatibility - NOTE it's a 885KB download :

http://www.osram.com/_global/pdf/osram_com/ecg_spot/pdf/2000_03.pdf

See page 5 - "NEW LABELLING OF DIMMER/LOAD COMBINATIONS"

******************

OK - if the transformer IS marked, but only has a "C" - that means it's a purely capacitive load and can only be dimmed by Trailing Edge dimmers (C-Bus Universal dimmer). If it has a "L", then the transformer is suitable for Leading Edge dimming, but the capacitance is still unknown.

The problem here is that too much capacitance will cause the dimmer to die - it effectively presents a "short sircuit" to the output stage of the dimmer, and the 1A C-Bus dimmer modules are pretty delicate to this type of overload. Sometimes the dimmer wins, sometimes the transformer wins... in my own experience there's about 50% chance the dimmer will win.

I am unsure how Clipsal / CIS measures the input capacitance of transformers - it might well be as easy as using a capacitance multimeter across the input (230/240V) terminals? If so, then a trip to the local electronics enthusiest's store might be the solution.

And as others have said, the MCB on the outputs will do ABSOLUTELY nothing to protect the dimmer in the even of a fault - the requirement is only to comply with IEC Wiring Safety standards.

I hope that helps (a bit)

 

Hi John,
Thanks very much, that's been really helpful.
I've now spoken to the supplier, and have discovered that they're a rebranded Aurora transformer. I've spoken to Aurora, and (surprise surprise!) they don't know what the input capacitance is. They have however confirmed that they're suitable for Leading Edge Dimming.

When you say 50% chance of the dimmer winning, are you saying that the worst case scenario is that it just won't work, or that I'll knacker the dimmer channel?

I'd like to avoid buying additional C-Bus units if possible, purely for cost reasons.

Thanks Again,
David.

 

A four channel dimmer is about half the price of an 8 channel. While I accept that this is not the only cost (boards cost money as does space), it is not as bad as it sounds.

Mick