Need help with power switching on DALI/Emergency lighting circuit

Thread Starter

will brook

Joined Nov 10, 2017
Hi All,

First post here so be gentle, came here to try and narrow down an issue i have on a project in London. Its 9 floors of lift lobby lighting driven by 17-21 DALI drivers per floor and 6 emergency lighting supplies per floor for when the power goes out.

  • LD8CO300DK (Emergency DALI Lighting Driver)
  • LTECH DALI-75-24-F1M1 (DALI Driver)
  • LED array
    • 22V approx, 70W at full power
    • base circuit: 6 LEDs in series with IC to regulate current to 30mA
    • multiple base circuits in parallel
We have driver cabinets on 9 floors of a building.
Each driver cabinet contains typically:
  • LTECH DALI-75-24-F1M1
    • 17 pcs
  • LD8CO300DK
    • 6 pcs

In an ideal scenario each lift lobby (illuminated with 4.8W/m LED tape above a stretch ceiling membrane) powered by 17no. DALI drivers runs at approximately 70% (dimmed via DALI signal) then when the power goes out in the building the 6no. emergency lighting drivers should detect the power outtage and switch over to battery packs for 3 hours. Almost all of the time this does happen, with the exception of a couple of battery packs which arent charging and therefore dont activate.

The real trouble arises when the power turns back on and lots of switching has to happen in the driver box.

Also worth noting, the driver box is quite large and is split in two, it has a 'main body' and a 'door', there are 9 DALI drivers in the main body and 8 in the door, and 3/4 emergency drivers in each side. The 240V supply coming in to the box has been split to so as not to cause a huge inrush at switch on, so the main body of the box goes on first, then 5 second delay then the door powers up.

When the power switches back on after an outtage the sequence goes something like this.

1)Emergency drivers switch off
2)Main body DALI drivers (LED panels) switch on with the exception of the emergency drivers and panels
3)Main body emergency drivers and panels then switch on
4)Relay kicks in
5)Door panel DALI drivers (LED panels) switch on with the exception of the emergency drivers and panels
6)Door emergency drivers and panels then switch on
7)Ideally all the LED panels are back on at this point

When all of that switching is done with there is a random assortment, sometimes 1, sometimes 3/4 LED panels which dont power back up again. Its not localised to only emergency lighting drivers or just the DALI drivers.

All the components in the boxes are EMC tested so there shouldnt be any intereference internally within drivers themselves, although thats obviously not the case. Ive attached a photo of a section of the driver and emergency wiring so you all can see crudely what it looks like.

Any help on why things arent all switching back on would be greatly appreciated, Im at a loss and also well out of my depth!! I dont know what to do!! HELP.

Footnote: I was advised by the emergency lighting driver manufacturer to install ferrite coils to the main input of the emergency drivers (3 turns of LandN around a coil), this had no effect and in some instances made the situation worse, with more panels failing than before!!


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Joined Sep 9, 2010
When the power switches back on after an outtage the sequence goes something like this.
This would be a big challenge if I was standing in front of it, and familiar with that equipment. I’m neither. But it seems from a distance that “something like this” may not be good enough and that getting a more precise picture of what happens when might reveal the problem. Divide and conquer. See how each step behaves in isolation.


Someting sound wrong in terms of how this system was designed

I may know less than you do.

1. You are within the limits of the DALI bus? 30ish, I believe.
2. terminators need to exist at the beginning and end of the bus.

You have a bunch of integrated backup drivers and a central location which doesn't seem like the right idea.

I don't think you want powered off drivers or very few off at any time.

it's my understanding that the emergency brightness is programmed per driver, If it;s zero, so be it.
Somewhere where DALI originates, there is an EMG contact that you need to supply.

So, you have 24 v supplies that are capable of running the show and have enough back-up capacity to run selected lights at a selected dim.

So why all of the tiny batteries?

I have used a very wierd 24 VDC back-up system that was designed for access control. It had 8 class II circuits that could be enabled.

I used something like:

Install sheet:

Reason: I needed to run some strobes primarily and wanted to keep the wiring Class II. You have 8 amps total, but each circuit is a Class II circuit. The full 9 amp capacity would require conduit.

These are primarily designed to power access systems and keep locks open during a signal from the FAP. I think it;s capable of delivering a NO AC Power type of signal.

Battery placement was in a separate box.

The PTC version might have been better for you. Just class II outputs, no switching.

Surges shouln't be a problem with LEDS or an active battery charger. I think someone took a simple problem and really made it complex,

More info (checklist of sorts):

Here EMERGI-LITE ME DALI Emergency Lighting 23R1.pdf is info on a dedicated emergency lighting system controller.

Dali Emergency:

Odd device:
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