KNX Lighting - Central vs Distributed

[II0]

I’m planning for a house renovation and looking at lighting options. 

The cost of the Loxone dimmer modules are too expensive which is leading me to KNX.

There are 2 options which standout:

1) Install 8-way Theben 8-2 modules in a central location.

2) Use “inline” dimmers in the ceiling of each room. The MEAN WELL PWM-60-KN Series fit nicely. The plan would be to run multiple led spots in parallel from each dimmer.

Is anyone able to share any real world experience as to which option works best?

I’m going around in circles between the flexibility that option 2 provides for future changes vs option 1 which could realistically just use relays for most lights which are non-dimmable. 

[Rob_in]

Hi

DMX controllers are much cheaper than KNX. We use EldoLed Lineardrive 180D here. They work very well. I use them to drive 4 monochrome LED channels rather than RGBW. Because of this, and because our house is small each light circuit is wired back to our panel with 5 core 1.5mm2 cable. 1.5mm2 not for current but to avoid voltage loss. We have 24v ConstaLed drivers from Voltus.de - sadly these are not cheap but the whole system works very well.

If you have a large home you could run DMX (just pull cat7 cable so you can upgrade protocol in the future) to strategic locations and then place PSU+dimmer in that location for nearby rooms.

If your cable runs from dimmer/controller to light fittings are short you might want to consider 12v LEDs. I have to say that while our system produces a very nice light output and is dimmable right down to 1% it's not the most economical in parts - mainly due to the ConstaLed LEDs. If you were using 12v LEDs think that would help a lot in department as are much more readily available cheaply.

All that said...

I am normally not shy about bashing Loxone on their value proposition but have to admit that if you have a Miniserver with tree that their RGBW tree LEDs aren't that outrageous a price when you consider you don't need any other hardware like a dimmer. Even using Loxone Tree cable for a light circuit doesn't seem such a crazy idea as if you ever wanted to ditch Tree you could use the 2 x 1.5mm2 cores for mains AC or for a DC voltage and use the 2x2x0.6mm pairs for control (such as DMX, KNX, ws2812*, etc). This wasn't an option when we built but I would seriously consider it now. I read Loxone Tree is a flavour of CANbus so in the distant future one may be able to drive with something other than a Miniserver.

HTH,

Robin

*ws2812 & various other flavours of addressable LEDs. Hmmmm... normally used for 'decoration' but I have seen some 'high power' addressable LEDs coming to market and these could make an interesting choice. Like Loxone Tree LEDs they would not need a separate dimmer - just power and data signal to each and can be easily chained (in fact, that's what they are designed for). Probably only a choice for 'tinkerers' but I like the idea.

[Simon Still]

>>1) Install 8-way Theben 8-2 modules in a central location.
>>2) Use “inline” dimmers in the ceiling of each room. The MEAN WELL PWM-60-KN Series fit nicely. The plan would be to run multiple led spots in parallel from each dimmer.

On Saturday, 31 December 2022 at 07:33:28 UTC Rob_in wrote:

If you have a large home you could run DMX (just pull cat7 cable so you can upgrade protocol in the future) to strategic locations and then place PSU+dimmer in that location for nearby rooms.

If your cable runs from dimmer/controller to light fittings are short you might want to consider 12v LEDs. I have to say that while our system produces a very nice light output and is dimmable right down to 1% it's not the most economical in parts - mainly due to the ConstaLed LEDs. If you were using 12v LEDs think that would help a lot in department as are much more readily available cheaply.

What I did, and would do again, is have a 'hub' location on each floor of the house.  We needed somewhere for the underfloor heating manifolds anyway, but near them we have all the dimmers/psu's/relays for the lighting on that floor and then run individual cables (2 core, 240v rated 1.5mm) to the light locations controlled together (so usually pairs of ceiling lights).

The actual installs are a mix of constant current LEDs dimmed by 1-10v Loxone, DMX strip, DMX relays (and I think a few that are just on 24V relays from Loxone). But that should give me loads of options if/when anything needs replacing.  The 1.5mm cable is enough that there shouldn't be any significant losses at 24v or constant current LED (as only running <10W light down each cable) and means I could put 240v fittings in future if required.  I possibly should have run 3 core so there was an earth at the lamp location if needed but not many light fittings are earthed any more in any case. 

[g...@camleyphotographic.com]

I have used a finder 15.11 1-10v dimmer modules driven from the analogue ouputs (AO) from the miniserver. These are good and about £50 a channel, which is less than the Loxone dimmer extension.

 

Channel-for-channel they are narrower, which helps making cabinet space go further. Plus, I cannot currently imagine any other use for the AO terminals.

 

The downlights are aurora 240v led lights (£14 each) on a single circuit with 1.5mm wiring to the central Loxone panel. If you do not needed either the RGB or independent control, then the Loxone tree lights do look a little extravagant.  

 

For maintenance, by me or someone else, I would rather have the equipment all out in the open and not hidden in ceiling/floor cavities. I cam imagine getting very frustrated when trying to remember where a light dimmer was hidden, or trying to find one that someone else had hidden.

 

Best wishes, George

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[Rob]

Many on here have used White Wing DMX mains dimmers (WhiteWingLogic) which by all accounts are excellent and much better value than the Loxone dimmers, especially if you have a lot of mains circuits you want to dim.

[Jonathan Dixon]

Agree with the key points here but to clarify one thing, the 2x1.5mm2 cores inside Loxone Tree cable should not be used for mains, only low voltages (50V or less) as the tree cable  is SELV and terminates into SELV equipment, and there's not sufficient insulation to ensure you couldn't end up with mains on the tree cores if there was a fault somewhere in the wiring/ circuit.

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[II0]

Thanks for all the feedback.

My question was more about centralised vs distributed dimmers - not so much about the technology itself.

The reason for looking at KNX is that I need the extension module for switches anyway. I also like the idea of a simple cabling design with less bus cables running about.

Cost wise both KNX options I'm looking at are £50/dimmer.

One point I forgot to mention is that the centralised dimmer option is mains trailing edge. The other is 12V CV PWM. Not sure if that makes much difference in the real world? 

https://www.meanwell-web.com/en-gb/meanwell-pwm-60-120kn/all-item-number/all-output-current-a/12/

[II0]

Thanks Robin.

Is there any reason why you didn't go with the Loxone RGBW 24V Tree/Air Dimmer instead of DMX+EldoLED? Looks like the Loxone modules can be run as 4x 12V monochrome channels too which is an interesting option.

[Rob_in]

On Sunday, 1 January 2023 at 16:53:01 UTC+1 Joth wrote:

... the 2x1.5mm2 cores inside Loxone Tree cable should not be used for mains, only low voltages (50V or less) as the tree cable  is SELV and terminates into SELV equipment, and there's not sufficient insulation to ensure you couldn't end up with mains on the tree cores if there was a fault somewhere in the wiring/ circuit.

Urgh! That is horrible! :(

Don't feel so bad about having installed 5 core cable rated for 500v now. Sure, it's not twisted pair but imagine it could run AC or DC supply voltage with an RS485 signal and DC Ground  in the remaining 3 cores just fine.

Robin 

[Rob_in]

On Monday, 2 January 2023 at 01:14:20 UTC+1 II0 wrote:

Is there any reason why you didn't go with the Loxone RGBW 24V Tree/Air Dimmer instead of DMX+EldoLED

I was specifying components for our build in 2016 and these products weren't available then. IIRC one had to go DMX and the Loxone DMX dimmer was waaaaay more expensive than EldoLed.

For the record, I still wouldn't touch Air (wireless) unless as a very last resort. In a new build that shouldn't be necessary.

Maybe the Tree dimmers could be worth a look as you would avoid the need for DMX extension but you'd have to get someone else to comment on their dimming qualities. Also bear in mind what these could be replaced with in the future if you moved from Loxone and wire accordingly.

Robin

[Rob_in]

On Sunday, 1 January 2023 at 22:38:01 UTC+1 II0 wrote:

The reason for looking at KNX is that I need the extension module for switches anyway. I also like the idea of a simple cabling design with less bus cables running about.

Simplifying the number of standards you are using is always a good idea :)

Re: the Loxone KNX extension. Outrageous price! Especially considering KNX was built in to the MS Gen 1! I would seriously consider if a vanilla KNX IP gateway could fit your needs. Sure, it would be harder to code (just - Loxone KNX config is no picnic itself) but would be much cheaper and also not be limited to working with a Loxone Miniserver.

 

Cost wise both KNX options I'm looking at are £50/dimmer.

For the Meanwell PWM-60/120KN?

Bear in mind that is a single channel dimmer. So that's £200 for 4 channels which is way more expensive than our EldoLeds. However, I guess the Meanwell is mains powered so no need for a large DC PSU. However, I like having a large DC PSU as ours has a battery back-up which means our lights stay on even when mains power goes out.

 

One point I forgot to mention is that the centralised dimmer option is mains trailing edge. The other is 12V CV PWM. Not sure if that makes much difference in the real world?

Personally I would never touch mains dimming. Controlling a DC voltage with PWM is so much more efficient.

Of course, a lot of this is personal choice. Discussing lighting: so many options. Can of worms! ;)

Robin

[Stefan Latt]

If the home is not enormous I would do DMX and 24V using the same HW whether central or distributed. If you really insist on having 240V 7W lights use whiteving dimmer but that is whiteving is multichannel so not flexible for distributed (I have both solutions in different buildings) 

24V central or distributed

DMX extension

D4 DMX Dimmers  (same for RGBW and White Amazon.com: 4 CH Constant Voltage DMX512 Decoder RGB/RGBW Controller Din Rail Mounted 4 Channel Dimming Controller 5-24VDC : Musical Instruments 

24V downlights from Aliexpress $7 each 

24V regular E27 bulbs Amazon

24V also means you can directly wire any deck lights or whatever micro boat or truck light you find attractive

To Control 240V use DMX relay, Shelly Pro or Solid State Relays after the same D4s as mentioned above

Stefan

[II0]

Agreed. I do think Loxone is probably the best visualisation option + app out there at the moment. Even with the cost of the extension it comes in cheaper than many similar KNX native options (e.g. Gira X1 + S1) which surprised me.

[Rob_in]

On Monday, 2 January 2023 at 20:00:12 UTC+1 Stefan Latt wrote:

24V downlights from Aliexpress $7 each 

Really? I couldn't find much when I looked for 24v lighting there. Do you have  a link or what search text you entered or anything?

[Simon Still]

On Monday, 2 January 2023 at 04:37:38 UTC Rob_in wrote:

For the record, I still wouldn't touch Air (wireless) unless as a very last resort. In a new build that shouldn't be necessary.

I'd agree minimise Air but I installed a gateway and got a pack of 3 sockets and have found them really useful over the years.  I installed a couple of permanent 240v 5A 'lighting' sockets controlled by Loxone relays but location for 'table lamps' changes depending on your furnishing and the Air Sockets mean you can easily add a scene controllable lamp pretty much anywhere.  I've got one on my Coffee Machine, another ran a subwoofer (until that was replaced with one that had auto-on).   

I've got a couple of sonoff wi-fi sockets in use as well and they *usually* work fine but every so often get am annoying delay until they activate (whereas Air has been 100% rock solid) 

 

[Stefan L]

I revived much criticism from sharing contact info on the forum earlier so I sent you a direct email with info on where I sourced the 24V downlights. I think you can reach out to the manufactures on Alibaba or Aliexpress and just ask for 24V version

 

[Andrew Crockford]

Slightly off topic- but like Robin, I spec'd my home system in 2014, and went with 3x eldoLED POWERdrive 6060 600w, giving 96 channels controlled centrally by DMX, seemed best option at the time.  Constant current LED seemed the obvious way to drive LEDS  & looked like the way things were going at the time but the light fittings are getting harder to find now.

So now I roll-my-own light fittings (mostly MR-16 fixtures, but some other non standard as well)- I buy cheap 12v fittings, open- discard the LED & 12v driver and fit these instead:  https://uk.farnell.com/cree/cma1303-0000-000f0h0a40g/cob-led-neutral-wht-823lm-15w/dp/3227254  (when I bought them last year they were £2.10/unit.  Now £3.20/unit!).

Gives great lumens/watt.  Much better than the now discontinued megaman led bulb I was using.  Only suitable for tinkerers of course.

On Saturday, 31 December 2022 at 07:33:28 UTC Rob_in wrote:

[Rob_in]

On Tuesday, 3 January 2023 at 12:17:22 UTC+1 Stefan L wrote:

I revived much criticism from sharing contact info on the forum earlier...

The problem is you tell everyone that these are available at AliExpress, which is a legit (with caveats) retail site but when asked for more details I was given an AirBnB website and Hotmail email address.

Robin

[Stefan L]

Right, but I think most manufactures on Ali would be able to provide the 24V version even if it is not a line item

Payment in my case went through Alibaba (legit?) As long as you pay with a card you are protected in most cases. 

I apologize for sharing our own Airbnb unit (we live in it at the moment) with you to show some pictures. 

I think these 24V downlights provides the most cost efficient reliable solution today. 

I apologize for sharing our own Airbnb unit with you to show some pictures. 

Picture of the light attached