Dimming 4 X Halagen down lights?

I am about to build a new home and would like to dim 4 x 50watt halogen downlights using a standard 1 amp C-bus dimmer channel. That is 4 lights on the one dimmer channel using of a L5508DA1.

1. Is it possible to do this?

2. What electronic leading edge transormers would you recommend? What is the most reliable?

Thanks guys,

Fleetz

 

Hi Fleetz

Your 1A dimmer channel has 240VA of rating, which means 60W per downlight. Take 10% off for "safety overhead" and you can use 54W per downlight. That means almost any decent electronic transformer is OK.

I'd recommend Atco Speedy or Possum transformers. Do NOT use Osram transformers, and I'd recommend NOT to use cheapies supplied by lighting shops, irrespective of what claims the manufacturer makes for them. You would only save a few bucks, which is nothing in the overall scheme of things.

To save money you could use 2 only 105VA Speedy transformers (each running 2 lamps) and save a few watts as well. Speedy is available in 70VA, 105VA or 150VA, Possum is 60VA only.

Note that the official CIS documents say only 3x70Va transformers per 1A dimmer. That is because they have no control over how electricians and home owner install those transformers, or what they connect to them. If you ensure that you only ever use 50W lamps, then 4 per dimmer will be perfectly OK.

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A good power-saving option would be to use Osram 35W IRC lamps - they give the same amount of light as the BEST 50W lamps, and probably twice as much as the cheapy "no-name" chinese 50W lamps.

Also I recommend setting a max level on the dimmer channel (from toolbox) of (say) 95%. Dimming the LV lamps by 5% will double their life, dimming by 10% will quadruple their life. So, use high quality lamps (Osram or BLV have the nicest "beam distribution") and extend their life with permanent dimming. Nobody will notice the dimming of 5%.

Note that it's not worth "permanently dimming" LV lamps much more than 5% or 10%, because the silver reflectors still seem to deteriorate at the same rate anyway (the reflector is really only rated about 5000 hours, to match the bulb rating). In own my house I find that unless I use chinese cheapies that the bulbs (glowing bits) never blow, but the reflectors go from silver to clear and no light gets down into the room after a few years !

Hope that helps. JC

 

Hi John,

Excellent feedback and it will be adopted to the letter! Great feedback.

Many thanks,

Fleetz

 

Hi John,

Hope your still around.

I not with interest that you do not reccomend the Osram electronic trnasformers. I have been asking in a dedicated thread about how they perform and their reliability and no comments todate.

I asume your were referring to the ET-Redback transformer which OSram claim as new and improved...not exactly sure what has improved.

Anyway I have great success with the Atco 60VA Possums so I will probably stick with them for this job. I was hoping to get some positive feedback on the Osram Redbacks as they fit through the downlight opening without the need to pop the fitting from the ceiling should the transformer need replacement.

I have a 6 X 35W IRC Osram Decostar on a 1A dimmer circuit based of your previous post this should just make the suggested 10% safety overhead.

Regards,

Fleetz

 

GU10 downlights dont need a transformer. 240V halogen.

 

JohnC has not logged in since April 2009. I miss his contributions in lighting. He had a lot of experience to share.

Does anyone know if JohnC is still around?

 

Osram outlawed??

I have used the osram redbacks and have had no issues with the 1A dimmer channels, but you have me worried now what is so wrong about them they have the same nF as the possums on comparason and the same VA??

Calm my nerves please....

 

Rest easy http://www.osram.com.au/_regional_AP...ure_lowres.pdf they are 33nF and 60VA

no one has any horror stories so one assumes they are a reliable alternative to the Possums, on a recent quote they were nearly $4 cheaper too.

I will probably go the Redbacks and see how they go...

Fleetz

 

havent had any issues with the redbacks, been installed for 3 years now no problems, haven't changed any yet.

halogens always at a dimmed level wont necessarily last longer either, the level of the globe must be at a high enough level for the gas to rejuvenate or recycle inside the globe if its not hot enough to recycle the gas inside you shorten the life of the globe. correct me if im wrong

 

The life of halogens and the effect of dimming is discussed in this thread:
http://www.cbusforums.com/forums/showthread.php?t=1558