Anyone know of any resources for planning a 12v domestic lighting system.

I cant seem to find much about it online. I have the opportunity of wiring a barn conversion wholly for 12v LED lighting from a single supply point. In theory I can then drive the entire domestic lighting requirement from a combination of SLA batteries/microgeneration (PV, wind) and mains transformer/charger for back up/night-time Economy 7 charging.

Current transformer based systems demand very short cable runs (obviously due to the higher current and the skinny wires they supply), if one were to use thicker core cable would that prevent too much losses?

Have you checked out any sites for caravan / boat electrics, which usually run at 12 / 24V ?

Some time ago I was planning a long run for a 12V system & a guy I spoke to [sorry can’t remember the co] told me that 10²mm cable was capable of 50m runs

12volt.com

labcrafts LED striplights are excellent

I upgraded the cable in my van and everything got brighter. Cable runs in there are only 3 – 4 metres.

I’d opt for a conventional wire in the house with localised LED transformers then handle all the CU end of the lighting circuit using some sort of battery driven UPS hooked into the mains for resilience.

I have used these guys for lift interior lighting, they are a good bunch and should be able to help.

Its is going to be an “industrial solution” you need, LED with relatively low current draw will be the best solution I feel.

LED lighting

Not knowing much about eletrickery I asked an electrician about this once. Seemed to me that given the large number of wall transformers and low voltage lighting in most houses it would be sensible for them to have a normal 240v ring and a secondary 12v ring (presumably with different plugs).

But he said the same thing about 12v not working on long cable lengths, so I guess unless your house is the size of a caravan it isn’t practical.

See above my post regarding industrial LED lighting, it is a modern practical and efficient way of lighting.

Believe me it does work if planned and executed correctly.

cheers all. Monty – thanks, thats what I was thinking, there must be a “lossless” wiring approach somewhere out there.

Transformer/inverter losses are huge, it would really pay off if I can retain 12v from source to use.

uplink, cheers, I was expecting larger diameter cable should be able to cope.

I’ve seen LED direct replacements and they’re WAYYYY below the nice even light distribution of a normal lamp, so it would take careful planning and knowledge of the fittings. The cable you need would depend entirely on the distances and the number of LEDs run, not really something that can be generalised but I would have thought it better to go with localised transformers – you can still go down the battery-power route using a good quality inverter without too many loses.

Transformer/inverter losses are huge, it would really pay off if I can retain 12v from source to use

so are wiring losses at low voltages. The waste is proportional the the square of the current – which is why the power grid runs at 125kV!

Planning layout and spec isnt a problem as we have a clean sheet and can make the most of defined good practice and industry experience without being forced to simply replace 240v units.

and even better, searching around I found this!

http://www.litewave.co.uk/led_shower_head.asp
How cool is that?!??!

sfb – I thought losees were a function of resistance too, so can be mitigated with low resistance wiring.

Actually a good quality inverter should perform near 90-95% efficiency and decent transformers should be around the same, leading to ~19% loss worst case, unless you buy cheap tat. However that would then require many transformers which is more costly than a single-point large transf. Swings and roundabouts.

Stoner – power losses are given by I^2 R, the I is the dominant factor in high current circuits.

I thought losees were a function of resistance too, so can be mitigated with low resistance wiring.

yes, but copper is expensive 🙁 You can halve the losses by halving the resistance, but the wire costs twice as much.

just as a side issue there is always fibre optic lighting, no volt drop there me thinks

looks like Ill need to get the calculator out and work out what the capital cost of the two appraoches would come to…one with more copper and less electronics, the other with less copper and more electronics…

must be fairly rare though monty, and uber expensive? Interesting thought though.

just as a side issue there is always fibre optic lighting, no volt drop there me thinks

I dont think that’s going to deliver the level of light I need 🙂

LED lighting combined with fibre optic, low voltage, low energy, low maintenance.

I did my home up last year and regret not considering it.

but see its still very dark in that room monty, looks like a candle-light dinner rather than a house where you can live and do stuff with decent light. Same thing seems to be the case with LEDs, unless you wildly scatter them over everywhere with joyful abandon, its a dull and sharp.

ouch, £700 for a room’s worth (100w) of light. No thank you! 🙂

http://www.unlimitedlight.com/bathroom-lighting.html

We’ve completed major renovation work on our kitchen, and the whole lot is lit by LED lighting now.

Colour wise it’s virtually identical to halogen. It’s all 12V, and a mixture of LED downlights (equivalent to the halogen ones), and LED “ribbons”, which light the inside of cupboards and the work surfaces and so on.

Things we learned:

1. When hunting for the halogen replacements, do not get the ones that look like an array of normal LEDs. They’re useless and have a limited lifespan. Instead, we’re using ones which have a gridlike pattern of surface mount LEDs, which kick out more light than their halogen friends and have the right colour.

2. The LED ribbons come in a selection of colour temperatures. Make sure they all match. Ours look exactly like halogen light.

With regard to your plan, I would keep 240V as long as possible. Get a cheap inverter or something.

cheers flaperon.

do you have a link to the LEDs with gridlike arrays you mention?

Actually a link to his LED tape supplier would be handy too 🙂

I think he is thinking of the luxeon/cree based LED lights, rather than standard 5mm body diodes, luxeons are multiple LEDs in one package, the same sort that go into the high-lumen output LED bike lights.