L5508D1A dimmer

Hi,

It could be a dump question, but I want to know why there are to two active and two neutral on L5508D1A dimmers. Is the second for c-bus power supply?

 

You are correct, the second terminals are for the inpternal supply (P product) and also the C-Bus power supply (non-P product). The unit will not operate if you don't connect these.

 

Thanks Newman

 

And should be on the same phase. We love to watch those triac's working.

 

Sorry to ressurect an old thread... but

Hey - If the 2 supplies have to be on the same phase, then WHY aren't they internally wired ?

It drives me mad making up the loop cables between those 2 connections !

John

 

Having the two supplies enables you to wire a cbus control circuit that will power cbus units only and have the loads connected via a seperate circuit breaker so that if a short occurs within a load you dont lose the entire cbus system.

regards allgo

 

Here is another question regards to L5508D1A.
We are puting a group of 4 lights on each channel, total output 1A. Now the supplier said, you cannot do that for lighting application, you should have 2A dimmers. Does he speaks gibrish or we are missing something?

 

Hi,

There have been lots of discussion regarding this, I suggest you use the search function.
Also there is a formula on the CIS site that you can use.

But as a general rule, 4 lights (I presume you are talking 50w downlights?) will be ok as it is not 1amp but no more.
If you want to run exactly 1amp, I would suggest splitting the lights up or using the 2amp dimmers. Running a 1amp dimmer at max is not advisable, from my experience anyway.

Cheers,

 

Thanks Nobes,

It makes sense now. Yes I am talking about 50w downlights. I will follow your advice.

 

On the subject of maximum loads: I can across an interesting bit of info the other day, the USA wiring regulations require that the maximum load on a switch, relay, contactor or dimmer should be no more than 80% of that switch or dimmers nominal rating so that in the case of the 5508D1A where the channel is rated at 1A - ie 240W @ 240Vac the maximum load allowed at 80% loading would be 192W.

(of course they work at 120V etc so the same sums would be different in the States)

Now that's not a bad way to spec a job as you know you will get reasonable life out of the product - it is not being run at 100% all the time (and note the US regs will not allow higher than 80% even if you promise to always run the dimmer at 50% brightness - coz they don't believe that you or who ever lives in the house will stivck to it).

Also it covers the situation where you install a circuit controlled by a dimmer with 60w lamps and some owner down the track decides to put 75W globe in.

 

Also keep in mind that 12V 50w downlights are not just 50w of load...

On a iron-cored transformer they consume about 65w. That means a maximum of 3 (195W) on a 1A dimmer channel

Using Electronic Transformers you still lose about 4-5w, for a total of (say) 55w per lamp. That means that 4 use 220w which is very close to the maximum rating of the 1A dimmer and not recommended.

Ummm - the dimmer is still loaded with the same amount, irrespective of the brightness setting. Keep in mind that a 1A dimmer can only dim 240w @ 240V - you can't run 480W through it even if you did set it to maximum of 50% brightness !

 

Hi,

One power terminal is for internal module circuitary and other for the supply to dimmed outputs.

 

I'm not that dim

John C

Ummm - the dimmer is still loaded with the same amount, irrespective of the brightness setting. Keep in mind that a 1A dimmer can only dim 240w @ 240V - you can't run 480W through it even if you did set it to maximum of 50% brightness !

Hate to disagree (and I am not suggesting anyone set up a system to operate like this) but if you set a 250W dimmer to (say) 30% brightness on a load that was a nominal 500W then my understanding is that the total power being disipated (by the TRIAC and therefore heatsink) would be < 250W. And as soon as you increased the brighness to >250W the TRIAC would overheat in short order.

In any event the USA 80% rule that I alluded to was that it would not be allowed to run a 250W dimmer at 250W only at 200W (80%)