24v lighting circuit - good or bad idea?

[SBMS]

Looking at loxone home automation. Seems that life would be much easier and cheaper with regard to downlighter dimming if I went for 24v lighting circuits for downlights. Has anyone else done this? It seems very difficult to find 24v fittings but I assume I can use 230v fittings that don’t have lamps, add my own gu10 24v lamps and then can dim from the 24v loxone dimming relay (4 channels for £70 odd). 
 

Any downsides to the above?

[-rick-]

I've never heard of 24v GU10 lamps. I'm not sure I'd want to try and make my own especially as the best lights are ones with sophistcated lenses not just a bunch of leds on a board. If you did want to do that I would go for MR16 as a connector.

 

What you'd like to do does seem fairly optimal as a way of doing things. I'd like to do something similar. But I've not really found anyone selling much suitable. Especially as I want CCT controllable lights (at least in some places) so that I can alter the colour temp by time of day/activity. You either get 'smart' lights with their own wireless interface or dumb lights in MR16 (12v) or GU10 (mains voltage) or completely custom fittings. I think loxone do their own multi-colour light to connect to their controllers but its really pricey and didn't seem that good.

 

Oh for an industry standard option in this space. Most people just want something they can retrofit to existing system.

Edited Sunday at 15:19 by -rick-

[-rick-]

BTW Soraa do some high quality externally controlled lighting so it's one place to start looking. But it's expensive and still doesnt really fit the bill. They also look like they have been bought out/merged since I last looked so not sure their products are the same/same quality as when I last looked.

 

https://www.ecosenselighting.com/products/soraa/

[Nickfromwales]

23 minutes ago, SBMS said:

Looking at loxone home automation. Seems that life would be much easier and cheaper with regard to downlighter dimming if I went for 24v lighting circuits for downlights. Has anyone else done this? It seems very difficult to find 24v fittings but I assume I can use 230v fittings that don’t have lamps, add my own gu10 24v lamps and then can dim from the 24v loxone dimming relay (4 channels for £70 odd). 
 

Any downsides to the above?

230v fittings have current ratings to suit, and when you drop the voltage the current shoots up, simple V/I/R calcs will show you the impact there.

 

Also, you'd need to run bigger cables too, to combat voltage drop. Not a huge issue in a smaller house with a centralised 'cabinet', but if one end of a larger dwelling you will find it prohibitive / impractical I think.

[-rick-]

Looking at Nicks reply makes me wonder if I've answered a different question.

 

The 24v dimmers are generally for LED strips not fittings. If you want to use them to dim bulb type fittings, one idea is to run two MR16 bulbs in series from one dimmer channel. That should just work with standard dumb MR16 bulbs. Of course if one bulb failed it would take out both fittings but that might be a good trade off.

 

MR16 is designed to cope with 50W halogen so should have no problem with anything you can throw at it LED wise.

 

Do keep the cables to the controller pretty short though. Running long leads with PWM dimming signals is a recipe for issues (thats ignoring the voltage drop due to cable length).

[SBMS]

1 hour ago, -rick- said:

Looking at Nicks reply makes me wonder if I've answered a different question.

 

The 24v dimmers are generally for LED strips not fittings. If you want to use them to dim bulb type fittings, one idea is to run two MR16 bulbs in series from one dimmer channel. That should just work with standard dumb MR16 bulbs. Of course if one bulb failed it would take out both fittings but that might be a good trade off.

 

MR16 is designed to cope with 50W halogen so should have no problem with anything you can throw at it LED wise.

 

Do keep the cables to the controller pretty short though. Running long leads with PWM dimming signals is a recipe for issues (thats ignoring the voltage drop due to cable length).

Is MR16 not 24v? I assume the 24v dimmers wouldn’t work?

[-rick-]

MR16 is 12V, I believe historically AC, though I think DC is common too.

 

A 24V dimmer designed for LED strips should I think be able to drive two basic 12V MR16 LEDs in series assuming you are driving simple LEDs. I wouldn't expect it to work with LEDs that have any smart features. Even 'dimmable' ones might be difficult. To be clear, when I say work I mean work with the dimming function of the loxone driver. All will likely work if the set point is 100%.

 

A 24V dimmer designed for LED strips will likely be able to supply enough current to drive multiple sets of 2 in parallel but if you wired a single MR16 up to it (or multiple in parallel) the 24V will almost certainly pop them given they are designed for 12V (even if you set the dimmer to 50% - it doesn't work like that).

Edited Sunday at 18:12 by -rick-

[-rick-]

I checked, my old MR16 drivers are AC. First hit for MR16 driver now came up with a DC driver.

[SBMS]

Thanks all. Im a bit worried wiring  two 12v mr16s to 24v and was already concerned about putting non standard lighting circuits in.. I think it sounds like I am probably best off with mains downlights and trailing edge dimmers. The loxone 4 channel mains dimmer is ridiculously expensive so I’ll probably go for the whitewing dmx. I think I’m better off going for gu10 fittings and then getting something like a Philips master DimTone?

[-rick-]

That sounds like the best approach to keep things standard and understandable. GU10 seems to have won the war for replaceable bulb fittings even though its the worst format for dimmable LEDs.

[Alan Ambrose]

Actually I think your 24V idea is a good one. It’s a bit nonsense converting 230V to low voltage all over the place. These days, the only things actually needing 230V are the higher power items, appliances etc.

 

Regarding current and cable size at low voltage - the whole point of LEDs is that they are much lower power than the old fashioned lights they replace. Say you’ve got 100 off 5W leds in your place - that’s 500W or 20A and that’s with all your lights on (and they won’t all be on the same circuit).

Edited yesterday at 06:48 by Alan Ambrose

[G and J]

Standardisation and volume production are key to cost effective reliability.  Yes, maybe if we were designing our domestic systems from scratch we’d go low voltage dc.  But we aren’t.  And the range and variety and price of ac control options are impressive. 
 

Be a bit careful with dc ratings.  Some switches have a very low dc current rating compared to their ac rating (I think that’s due to arcing). 
 

And whilst it’s a seductive argument to replace all those ac-dc converters in each light bulb in reality a system would probably have just as many dc-dc converters which are pretty similar. 
 

A while ago I investigated dc domestic lighting, spurred on by the thought that I could easily battery back 12v lighting circuits and improve efficiency. But the argument disappears when one considers the efficiency of modern ac coupled battery units.  
 

So instead I settled on a split CU and an ac coupled battery unit with backup capability.  Simples. 

[Alan Ambrose]

Yeah, each to their own and you have to choose carefully where you want to innovate (if anywhere) and where quick and off the shelf is the order of the day. It’s Indicative though that Loxone lights are 24V and I think that style of technology (not necessarily that company and pricing) is where we’re heading eventually.

[-rick-]

1 hour ago, Alan Ambrose said:

Yeah, each to their own and you have to choose carefully where you want to innovate (if anywhere) and where quick and off the shelf is the order of the day. It’s Indicative though that Loxone lights are 24V and I think that style of technology (not necessarily that company and pricing) is where we’re heading eventually.

 

Yeh if a loxone bulb cost £20 rather than £80 they might have something but the prices compared to standard off the shelf are crazy. I'm guessing the price on the website can be got down a fair bit through a bulk order but still. Having looked again at their website thanks to their thread at least they now seem to have fittings with decent lenses, etc.

 

I doubt we will get there as standard in domestic properties in any time scale relevant to this forum.