Flashing lights controlled by 4 channel dimmer.

Hi this is my first post, I'm looking into the problem as described below.
The system went in about 7 years ago. All worked well,I’ve been told, until they moved a wall in an office and moved a single gang C-Bus light switch, a few months ago. From then on 4 groups of lights in that area go into a flashing fault, The groups flash independently of the other 3 groups , and not aways at the same time. This only occurs when the light group is dimmed.
They were set at a min of 52%, I raised that to 65% but it just took a longer time from being dimmed to start flashing. It's not a constant flash the length of time between groups of flashing varies.
Turning a group off and on, they come back on full, then dimming then restarts the length of time before they start flashing again. there is no effect on the other groups that are flashing when that is done.
All 4 groups come of a L5504D2A dimmer, the channel indicators don’t blink or flash.
They are having no problems any were else in the building.
We are not the first electricians to look at this. The last one’s replaced the dimmer ( that’s the L5504D2A, not sure what had been there before.)
The 4 circuits are driving Guild 13W led lights with Optoronic OTE 15/220-240/350 PC drivers. 2 circuits at 12 light, 1 at 18 lights and 1 at 25 lights.( currents are below ratings of dimmer). These have not been changed since install. ( so they did work ok)
There are 102 units on the system

• 1 x 4 channel relay,
• 2 x 8 channel relays,
• 6 x 12 channel relays,
• 1 x 8 channel dimmer,
• 2 x 4 channel dimmers,
• 15 x single switchs,
• 3 x 4 gang switch,
• 69 x motion sensors,
• 1 x PE cell,
• 1 x 4 channel aux relay,
• 1 x SC5000CTL2,WE touch screen.

I’ve got a couple of questions, as I did my C-Bus course over 10 years ago and have used it about 5-6 times on small reprogramming /replacement of units.

1. The number of units on the system 102 ? It had been working OK.
2. There could have been 4-6 more meters added into the circuit with the movement of the switch, would this have an effect?(total cable length)
3. Would 31LCDA ( load correction devices) make a difference if installed on the dimmer outputs? They had been working before. willing to try this.
4. I also noticed that not all pairs at the switches have been joined to daisy chain onward. (greens and browns)? Worked before.
5. I do have a L5504D2U Dimmer I could swoop in, but don’t think that’s the problem as the dimmer has been changed once with the problem the same as before.( the staff said the problem came back slightly worse the day after it was replaced)

If you are able to give some advise it would be much appreciated.

 

Hi
Are the LED lights suitable for dimming (leading or trailing dimming) the dimmer you are using is a leading type dimmer.

On that dimmer you are using there are terminals on the far right Active and Neutral they must be on the same Phase as the Active and Neutral on the far left side of unit if not dimmer will do strange things.

Do lights flicker at any time of day or only at certain time of day. If you are in Sydney supply authority turn Hot Water on at certain times by sending a signal over the mains and sometimes this causes lights to fluctuate when dimmed.

I don't think you have a CBus comms issue it sounds like a 240 volt issue.
1, 102 units would be OK.
2, extra cable length should be OK.
3, 31LCDA may help.
4, Green and Brown not needed.
5, L5504D2U May fix problem??
Good Luck

 

I note you said that this system worked before any alterations but I question that because:
The number of drivers connected probably exceed the 300uF capacitance per channel limit.
the fact that the min dimming level was set so high.
I doubt a 31lcda would resolve this issue but the L5504D2U may be more successful with this being a universal dimmer and not affected by capacitance issues.
I presume that when the lamps are on 100% there is little or no flashing.

 

Thanks for the reply, The drivers are suitable for leading and trailing edge dimming ( so there spec sheet says)
The 2 inputs to the dimmer are on the same circuit as they are linked together. the lights flicker during the day when they were dimmed for fault finding, they are normally dimmed at night on a auto setting, so people can't see in clearly as its a control room.

 

Thanks for the reply, yes there is no sign of any flicker when the lights are not dimmed. I also noticed that the max for the dimmer channels is set to 92%, ( not sure the reason for this ).
I think I will try the L5504D2U dimmer, and try to quiz more of the staff about the history of the system.Would it be worth trying a 31LCDA on each channel?

 

The LCDA was designed to provide the electrical characteristics of suitable load for the dimmer when the connected load was beneath the recommended minimum load for the dimmer.
What may happen if you only have one or two LEDs connect to is the LEDs flicker in the OFF state due to insufficient load. The 31LCDA should help with this issue.
None of the present dimmers for C-Bus were designed for use with LEDs hence work arounds have been developed, which are not always great.

 

Thanks for your help and advise, Changing out the Dimmer to the L5504D2U solved the problem.