24vdc lighting for residential home?

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greenbone

176 posts

Master Geek

#215532 1-Jul-2017 09:46

starting a new renovation and considering using 24v LED downlights for all the rooms. supposedly becoming more popular method in EU

its similar to installing LEDs anyway except it uses one or two centralised drivers as opposed to having individual drivers connected to each LED (or integrated)

voltage drop accounted for, i dont see any drawbacks to this, advantage being i get to run and install the lighting cable and fittings myself

i know theres a few electricians with opinions here, would love some input please

richms

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#1809978 1-Jul-2017 10:06

There will still be drivers in each LED, Other than being cheaper to automate them I dont really see any huge benifit in them.

Downlights are now usually done with a socket in the roofspace since they have _finally_ bitched at sparkys who leave single insulated cable hanging out of the drivers and they are never designed properly to let you terminate 3 or so 1.5mm twin and earths in them, so changing downlights over is an unplug/replug operation mostly, which is something you can do.

They still need to meet the needlessly bureaucratic insulation standards of the building code when going into a residential ceiling space so what have you found in 24v which is labled for CA/ICF rating etc?

Richard rich.ms

k1w1k1d

1519 posts

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#1810013 1-Jul-2017 11:15

You will also need to check with your insurance company, as they may still require all wiring, even 24v, to be installed by a "competent person". They may not consider a home owner to be competent.

There will also be an interface point between the 240v and 24v systems that will have to be done by a registered electrician?

Aredwood

3885 posts

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#1810023 1-Jul-2017 11:43

What 24V power supply would you use? As it would have to be rated to handle all lights on at the same time. And still have good efficiency when only 1 or 2 lights on. And what about extractor fans? They will still need mains power. But you can't have mains and ELV switches on the same panel.

And because you still need drivers at each LED overall power usage will probably be higher than simply using mains due to the extra conversion stages. As LEDs use constant current power.

And what light switches will you use? As mains switches say to use for AC only. Sure they will probably be fine for 24Vdc but have they been tested and approved for that?

greenbone

176 posts

Master Geek

#1810063 1-Jul-2017 13:29

richms:

There will still be drivers in each LED

And because you still need drivers at each LED

i dont quite understand this. the LEDs im testing are 24v, powered from a 24v power supply. if there were an integrated driver, surely my test setup wouldnt work?

these are the LEDs im using for testing

im assuming to legally sell a product with "DIY - no electrician required" on the shelf of one of NZ largest retailers, that 24v installations are ok for homeowners to DIY

the switches are fine (24v bus), im not installing any 240v myself so extractor is ok

richms

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#1810074 1-Jul-2017 14:19

Led dies thenselves are non ohmic devices that need an accurately controlled current in order to have any chance of constant brightness and a long life. Some cheap fittings will just use a resistor with the resulting disastrous results.

Whenever a fitting has a driver integrated into it, then it doesn't need to be an isolated type, just a basic buck converter. Will be not much change in efficiancy between one that takes 24v or 240v, add on the losses of the 230 to 24v power supply and greater cable losses and I dont see how you can get any better efficiancy from it. There will be greater losses in the external isolated drivers compared to a basic buck one but power supply technology has come so far since the first crap ones that they would barely get warm at all even when driving a 40-50w led.

Assume you have 60 watts total per room, that is then 2.5A per room, cable losses will be greater than if that same cable was passing the 0.25A that 230v would need for the same wattage, and the loss as a portion of what gets to the other end would be much greater. So thicker cables needed or accept a 5-10% loss in the cables as being ok.

The need for a centralized 30+A 24v power supply, and then since it is 30A the individual circuit protection you need and suddenly it all starts to look like a lot of work. Vs plug in a fitting at the point of use into well established wiring practices that any sparky can understand how it works makes doing it seem a very pointless exercise.

Richard rich.ms

greenbone

176 posts

Master Geek

#1810142 1-Jul-2017 17:14

thanks for the reply

richms:

Led dies thenselves are non ohmic devices that need an accurately controlled current in order to have any chance of constant brightness and a long life. Some cheap fittings will just use a resistor with the resulting disastrous results.

Whenever a fitting has a driver integrated into it, then it doesn't need to be an isolated type, just a basic buck converter. Will be not much change in efficiancy between one that takes 24v or 240v, add on the losses of the 230 to 24v power supply and greater cable losses and I dont see how you can get any better efficiancy from it. There will be greater losses in the external isolated drivers compared to a basic buck one but power supply technology has come so far since the first crap ones that they would barely get warm at all even when driving a 40-50w led.

Assume you have 60 watts total per room, that is then 2.5A per room, cable losses will be greater than if that same cable was passing the 0.25A that 230v would need for the same wattage, and the loss as a portion of what gets to the other end would be much greater. So thicker cables needed or accept a 5-10% loss in the cables as being ok.

i was planning on running 1.5mm tps for 24v

richms:

The need for a centralized 30+A 24v power supply, and then since it is 30A the individual circuit protection you need and suddenly it all starts to look like a lot of work. Vs plug in a fitting at the point of use into well established wiring practices that any sparky can understand how it works makes doing it seem a very pointless exercise.

in terms of cost, i think i would rather pay chargeout rate to a sparky to put in a couple 30A psu on their own circuits, than have him run cable and connect 40+ lights to 20 or so rooms. maybe its a false economy

the other advantage is good quality 24v dimmers are a lot cheaper than 240v

richms

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#1810212 1-Jul-2017 18:21

1.5mm is good for 10A normally, but as there is a low voltage you would want to have even less drop than the usual figures which are for 230v mains. A driver that is regulated (most of them) will just end up sucking more current to make up for the dropped voltage meaning that the power supply has to work harder, there is even more cable losses and unless you meter it and know what its ending up taking you could overload the power supply if you just summed up the loads and got one that was a little larger than it.

Are those LEDs dimmable tho? Generally LED "dimmers" are made for low cost LED strip type stuff, which has no drivers in them. To dim a proper driver which anything more than a watt or so should have needs the driver and the dimmer to speak the same protocol. Worst case is a raw PWM power chopping up which has to be done at low frequency with remote mounted LEDs because of emmissions, so you get flicker. DALI or even 0-10v stuff is way more expensive than a cheap dimmable driver and a wall mounted triac dimmer. While those have their own sets of problems once you find compatible ones they work well enough.

Richard rich.ms

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Fred99

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#1810391 2-Jul-2017 12:13

Hafele make hardware for joinery - sure enough their website seems to list these low voltage LED lighting systems for accent lighting, cupboards, shelves etc - not general room lighting. In that case an extra low voltage system makes sense on a lot of levels, including DIY and/or installation by joinery company workers.

I was at a new house last night - not sure if it was fitted with something like that hafele system in the kitchen. All cupboards/cabinets had LED lighting with a central control panel. that actually included ability to change RGB LED colour temperature, in case you wanted bright blue or red lights etc in your kitchen cabinets. That feature seemed a bit gimmicky to me - but OTOH an RGB LED lighting system unified through a central controller, where all home lighting could simultaneously be adjusted through a normal range of colour temp would be a good feature IMO.

I put lighting inside under-bench cupboards when I did our kitchen reno recently. I just used 12v silicone sheathed strip, warm white IP 67 (?) rated with the supplied PSU. For switching, DPST magnetic reed switches using the NO contacts. Inexpensive and very effective - probably only $50 cost to do the lot. Efficiency (lumens/watt) is probably very ordinary, however a metre of that strip (IIRC something like 200 lumens/metre) is plenty bright enough to light up a cupboard interior. In that case the strip can be mounted out of sight under the benchtop, for over-bench height cupboards or accent lighting etc, extra low voltage downlights like those hafele systems would be rather a more elegant solution.

pipe60

127 posts

Master Geek

#1812229 3-Jul-2017 20:21

Normally for general lighting have been using 13W Led DL so i think you will find they are not suitable in that role. 3.25w normally for pantry's/Wardrobe etc

greenbone

176 posts

Master Geek

#1812288 3-Jul-2017 22:41

pipe60:

Normally for general lighting have been using 13W Led DL so i think you will find they are not suitable in that role. 3.25w normally for pantry's/Wardrobe etc

these are only for my testing rig, you can get 3W up to 25W in 24v downlights