Look for lm/W (lumens per Watt) or 60 or higher (ie more efficient than CFL).

Do not fit LEDs in recessed sockets without ventilation since LEDs don't like heat and will have their life shortened.

Rgds

Damon

There are fire-rated luminaries for that sort of issue, ST, I believe. But probably still poor from a thermal management p-o-v.

Rgds

Damon

So you need to look for at least 100 Lumens per Watt from a decent quality LED? What would be a good Lumen figure from a 5W unit? I notice day light and warm white units vary greatly in lumen values. Would daylight be better suited to bathrooms and warm white for living accom possibly? On the LP's site would the V1 still be efficient or would it be worth paying for a newer V version. I also need to work out how my GU10 fittings will effect the life of the unit from a temperature point of view.
Can anyone recommend a good value LED with good lumen output? It seems from surfing with my friend Google that loads of LED's are, excuse the term, POOP. Would this be correct?
Thanks,
Gusty.

100lm/W is pretty cutting edge; I think around 60lm/W (so the same as a decent CFL) is pretty good at the moment and there are many sources for such.

Rgds

Damon

Thanks, all great information,
Gusty.

I would endorse your comments about MR16 LEDs, Beau. My workshop has been lit with an array of warm white MR16s for over a year now and I think they are superb. Best of all I've not had a single failure (yet), which seems to be quite a contrast with the experience of those using cheap GU10 LEDs.

I may have this completely wrong but, the problem with LEDs seems to be the change from 240V to 12v at each bulb. This heats up and the units fail. Would it be better to have a single transformer and use 12V LED units as designed for boats and caravans? Obviously you would have to take into account increased resistance in the wire etc but for single rooms such as the kitchen this would not be a problem.

Posted By: pmagowanI may have this completely wrong but, the problem with LEDs seems to be the change from 240V to 12v at each bulb. This heats up and the units fail. Would it be better to have a single transformer and use 12V LED units as designed for boats and caravans? Obviously you would have to take into account increased resistance in the wire etc but for single rooms such as the kitchen this would not be a problem.

Sure. I replaced all the 12V mr11 halogens in my bathroom with LEDs. You JUST need to change the halogen transformer for an LED driver. It also means I've been able to seal up the holes where the spots are recessed, as they're only 1.5W each without any funky electronics, so there's very little heat.

It's easily done for spot lighting, as a short run of DC wiring is no problem, but obviously for house-sized circuits you want AC. If you really wanted to hammer 12V I suppose you could wire up each room with it's own driver(s) for the local 12V circuit.

So you need to look for at least 100 Lumens per Watt from a decent quality LED? What would be a good Lumen figure from a 5W unit?

You'e answered your own question: 500 lumens

I notice day light and warm white units vary greatly in lumen values. Would daylight be better suited to bathrooms and warm white for living accom possibly?

Yes, possibly, but it's a very subjective area. I like nice blue ones, which is good because they're the most efficient, but the colour does vary quite a lot between LEDS. I've had nichia 5mm, luxeon I, luxeon III, seoul P4, luxeon rebel, Cree XP-G and erm 'another one' over the last decade and they are all different. The efficiency has gone from 7.5 lm/W to 109 lm/W over those LEDs. They all work fine, but when you put two side by side the colours are often quite different.

There really is no substitute for buying and trying. Having tried some XP-Gs I'm probably going to buy a pile more and use those. Although whilst I've been faffing new Cree LEDs have come out at 130lm/W.

I think the right way to do it is with an LED driver unit switched by each light switch driving the LEDs in that room. I prefer constant current drivers over constant voltage drivers, but either can work with reasonable efficiency and 12V is more comon than 700mA.

You can have a house-wide supply, but that has to run permanently so you need to be sure that its losses/efficiency are good at no-load and part load.

Here's the lamp I've made for my workshop as a test of the design. http://wookware.org/pics/house/LEDs/ (open the pics for the comments).
http://wookware.org/pics/house/LEDs/
That's 750lm for 28€ at around 100lm/W, and if the driver was any good, about 90% efficiency. For 20€ I can have a meanwell driver that is 87%eff, but it wants 5 LEDs to drive. That'll be too bright at 700mA.

Go to the candlepower forums for endless discussion of this sort of thing.

I didn't try too hard with that unit, but I don't think it's too hard to make something quite aesthetically pleasing reasonably cheap and very efficient. I keep hoping the chinese will do it for me, but I've not seen such a thing yet. Splitting those 3 LEDs into 3 separate units would produce better spread and less shadowing in the workshop.

I'd get better heat-sinking from using something finned like this: http://www.leds.de/en/High-Power-LEDs/High-Power-LED-accessories/Heatsink-51-x-51-for-HighPower-LED.html I might try that next.

Whoa; 3 comments on using a bus/whole house/room 12v system. Love to know more.

Posted By: JSHarrisI feel very similarly, to the extent that I'm going to build in a 12 V bus to my new build to run 12 V LED lighting. The 12 V MR16's I bought very cheaply from China well over a year ago have been excellent, no failures at all and a perfectly acceptable light output (although I've not measured it).

How do you propose to do that? There was something a while ago suggesting the cable would need to be massive to cope.

Posted By: wookeyI think the right way to do it is with an LED driver unit switched by each light switch driving the LEDs in that room. I prefer constant current drivers over constant voltage drivers, but either can work with reasonable efficiency and 12V is more comon than 700mA.

LED 12V transformers are different to Halogen transformers.

Posted By: pmagowanYou could switch the common transformer to avoid losses when the units are not on. That way your switching would remain 240V and you would have a shorter run of 12V. This would be more efficient and reduce risk of overheating at the transformer or wire. Obviously it is only possible where more than one light would be controlled by the same switch but this is usual for a string of spots.

Do you mean like Wookey on a per room basis?

I came across http://www.ledcentre.uk.com/ a while ago and they have a huge variety of transformers.

12V can be a problem if done incorrectly. I read up about it when rewiring a boat. Essentially, in lay terms, 12V finds it harder to go down the wire and thus it heats up. This is related to the load. i.e. If you have a large load you will ned a thicker wire to power it in 12V. LED lighting is a very small load (why I was investigating it for a boat with battery for power). So if you only use it for this the wiring does not have to be substantial. On my boat I can leave every light on for a week and still have battery power left whereas with a normal bulb it would just take one bulb a few days to run the battery flat.
I did use special wire with a fire quenching coating and I sized it for a less than 3% volt drop over the runs. In a house I don't think you would need to worry much as decent lighting cable would likely be sufficient for all but the longest 1 room runs. You can also get 12V circuit breakers for safety.

I might copy you JSH when I eventually get round to my internal works. I have taken a dislike to the CFL's (mini or otherwise) and have been very impressed with the LED's I used on the boat (in pretty damp, salty and vibration high conditions). They draw so little power and provide so much light and last so well that they seem the obvious choice. The problem up to now, as your post mortum shows, is the transformer electronics which your method gets around.

<blockquote><cite>Posted By: Ed Davies</cite>

It's a bit of an extreme case but if you do run 11 A down 1 mm² cable you'll get significant voltage drops.

Electrical resistivity of copper is 16.78 nΩ·m [1] so two-way resistance of 1 mm² would be 0.03356 Ω/m so 0.36916 V/m drop.


[1] http://en.wikipedia.org/wiki/Copper#cite_ref-0</blockquote>

True, but as you suggest, running twenty six 5 W LEDs on a single cable run is probably a bit extreme!

I'd guess most people wouldn't have more than maybe 10 of them on a single cable run, most would probably use a lot fewer per run. Using 1 mm² they'd get about 0.183 V drop per metre for ten 5 W LEDs, which seems tolerably low to me. Upping the cable size to 1.5 mm² reduces this drop to 0.081 V/m, so even a 5 m run would only lose around 0.4 V, or about 3.4 %

In my case the power supplies will be as close as I can reasonably get them to the lights (allowing for the need to get to them for replacement), so the runs of low voltage cable will be short, probably no more than a 4 or 5 metres at most. If push comes to shove I may just star wire the LEDs back to the power supply, virtually eliminating the voltage drop by reducing it to sub-1% levels.

Cable resistance is largely irrelevant if you use constant-current supplies. With a 700mA supply you get 700mA down the cable however many LEDs you use - just the voltage changes, and will rise a smidgen to cover cable losses if needed. If you put in more than 12 LEDs in one run then you won't be in 'low voltage' (<50V) territory any more. (You'll also have about 3000 lm which is an awful lot).

JSH I'd like to know where you get efficient drivers for £5. I've seen plenty of rather crappy drivers for that sort of money. (I've got one (12V) which claims to be 12W, but can't actually reliably start two 6W LED strips, and is only 60% efficient).

And "A 5 W LED draws about 0.417 A," is simplistic, or at least not stating your assumptions. That's true at 12V. Plenty of 24V LEDs around and in fact the LEDs themselves are almost always 3.6V, except for some multi-die devices.

It would appear that our schemes are identical - mains to each room and light switch, switching driver unit to supply low-voltage circuit to room lights. The only difference is that you are wiring up at 12V in parallel. I am wiring up at 700mA in series. 12V gives you more choice of luminaires and driver units. 700mA (should) give you better efficiency, it's easier to know what LEDs you are getting, and it's trivial to make your own.

A set of lights for the a living room (say 5 LEDs for ~1000 lumens) is 4.5€ for LED, 1€ for heat sink, £0.50 for diffuser. so that's €6 each for the lamps and another £10 or so for a decent driver. So that's £40 or so for the lot. There's still lots of people selling 1 module for more than that.

These look interesting: 680mA CC driver for 3 LEDs $5(!). http://www.dealextreme.com/p/9w-led-driver-circuit-input-85-265v-output-10-11v-680ma-42830 No quoted efficiency

These look better (efficiency >85%) but only 350mA models (fine but you need more LED units at a £6 each for same amount of light), and need to get a price: http://en.skyworthlighting.com/product-default-75.html

Cable loss is cable loss, whether you have CC or CV drive makes not a jot of difference, the power wasted in the cable is the same. The only difference is that the CC drive automatically compensates by upping the voltage at the drive end, something you could do by just turning up the voltage trimmer on a CV unit.

The majority of the SM PSUs I've bought so far (mainly Meanwells and Meanwell clones for charging big battery packs) have been around 90% efficient. The exceptions are some small single LED SM CC units I bought from China that struggled to get to 80% (but these were low voltage, 3.7V, torch driver devices) and a few single LED 12 V input 800 mA CC devices that I think were intended for incorporation in the base of things like MR16s. Oddly enough I bought some cheap 800 mA (ex-Petzl caving light) drivers from ebay that aren't switched mode, they are simple PWM and they are more efficient than the cheap Chinese SM drivers.

I've ordered a couple of smaller SM supplies just to see how good (or bad) they are. If they are like the Meanwell ones I have (and the Meanwell clones that seem so common from China) then they will probably be OK.

I've made a few LED lights now, bike lights, a reading light, a couple of torches, a bedside light and the 12 V lighting system in my workshop. Based on that limited experience it seems that the multi-LED units are generally more efficient than the single LED units, which is one reason I want to try the LED strip lighting idea. The Cree and Lumiled 3W LEDs I've used all run pretty hot and need good heat sinks, whereas the 72 LED 12 V MR16s barely get warm. In terms of light output it's hard to compare, because the single emitters look much brighter, mainly because they are a point source. The difference in colour temperature also makes a big difference to apparent brightness, and there seems to be a very wide variation in this with the "warm white" units.