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PostPosted: Thu Dec 24, 2009 5:53 pm 
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PostPosted: Fri Dec 25, 2009 12:47 am 
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Phosco152 wrote:
mazeteam wrote:
The round bit on the LED light pictured could possibly be a release mechanism.

That's a rather big knob for that! :shock:  :lol:
Maybe the designer thought having a big knob was a good idea!!!! :twisted:

:lol:  :lol:  :lol:  :lol:  :lol:  :lol:  :lol:

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PostPosted: Sun Dec 27, 2009 9:24 pm 
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Phosco152 wrote:

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I wonder how much power they consume? 100 LEDS say even if 1w each (and I suspect they are more than that) and say 50% efficient (which is not unreasonable for a LED)  would imply 200w so where is the power saving per fitting? There is only a saving if less luminaries are used, which wasn't the case for the ones I pictured.


sotonsteve wrote:
My local Texaco still has 400w mercury under-canopy lighting.


So let's say the LEDS are like the Luxon high power ones at 3w each. 100 leds is still 300-350w say allowing for the driver losses. (Answering my earlier question, a 3w LED is actually 3w input power so is less in light output "power" given they are not 100% efficient). Therefore they will save power over 400w MBF but not say 150w Quartz MH or say 70w CDM/CDO MH.


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PostPosted: Mon Dec 28, 2009 9:58 am 
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Something that I find with a lot of articles and product specification web pages about LED lanterns is a reluctance to mention power consumption. I would have thought this to be one of the most important bits of information to list, but so many people fail to mention it.

This includes articles about some Morrisons petrol station lighting up north, where a petrol station is 100% LED illuminated. The articles mention that the existing under-canopy lighting was 250w, but don't say what the new LED lighting is. Personally, I would have thought, for example, comparing 250w with a figure like 100w would be hard hitting for the article. Lack of mention of LED power consumption leads me to believe that they are actually a bit embarrassed by the under-canopy LED lighting. They mention the power consumption within the shop, and the overall power savings they expect.

Some articles do mention power consumption though. Remember the Southampton LED street lighting, where they said "look, we're replacing 70w with 45w". What they didn't mention was "look, we're going from  6000 lumens down to 2000 lumens".


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PostPosted: Mon Dec 28, 2009 10:14 am 
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Given that the best LED efficiency is around 70Lm/W which is less than PL-L operated on electronic gear, and that MH is over 100Lm/W, SON greater than that and of course SOX the best of the lot, I fail to see how LED lighting for the same lumen level can actually save power.  :?

I wonder if it is all a marketting gimmick - "ooh we've gone hi-tech with our lighting". The only potential "saving" is on relamping costs yet this has yet to be proved "in -service" due to the newness of the technology. Initial indications (traffic lights for example) would seem to suggest that lifetime improvements are still required. Perhaps the only saving grace as far as that is concerned, is that you don't often get a complete luminare failure, rather failure of individual LEDS. For traffic lights this "soft" failure method is probably more acceptable than a halogen bulb failing completely, and the longer lifetime in this application should save money compared to changing halogen bulbs.


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PostPosted: Mon Dec 28, 2009 10:46 am 
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Luxeon Rebel White LEDs reach an efficacy of 100 lumens per watt at colour temperatures of between 4000K and 6500K. At lower colour temperatures the colour rendering is better but the efficacy worse, so it is a trade off. The 4000K types have higher and lower colour rendering versions, one being CRI 60 efficacy 100Lm/W, the other being CRI 80 efficacy 81. I suspect those at Shell are possibly 4000K, no lower, so efficacy would be 81-100 Lm/W. The higher value is pretty good, but only comparable with ceramic metal halide, which is often the standard new fit anyway. Petrol station lighting tends to be 400w mercury, 250w quartz metal halide or 150w ceramic metal halide under the canopies, so can LED lighting save power from 150w?


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PostPosted: Mon Dec 28, 2009 12:02 pm 
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Those figures are for high end spec LEDS, Luxeon have always been the technology leader. The article I found this time last year on LED efficiencies was unfortunately lost with Ukastle 2. A more "affordable" efficiency is around the figure I quoted. Current LED technology has reached the maximum efficiency that can be obtained reliability. Only the use of OLED technology will allow efficiencies compared to discharge lighting - well over 120Lm/W - the physics of the emitting junction structure of existing devices is the limiting factor.


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PostPosted: Tue Dec 29, 2009 3:27 pm 
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Today I bought a pair of Alpha GU10 LED colour changing lamps from B&Q for about £10. Ouch. Anyway, they are rated as being 1.3w each, which the manufacturers reckon is equivalent to 8w halogen. Put in perspective, the spotlights in my room were originally 50w GU10 halogens. We also have 50w GU10 halogens in the kitchen, which replaced 20w GU10 halogens which we found to be far too dim, so you can imagine how dim these LED spotlights are. Even adjusting for the fact that they are colour changing, the white versions aren't much better than for night light applications. Even as hallway lighting in phosco152's house they're not brilliant. Sorry phosco152.

Anyway, the two colour changing LED spotlights complement two multicoloured 50w halogen spotlights in my room. The lighting is on a dimmer circuit, which means the LEDs always have a bit of a flicker. Dimming the dimmer switch doesn't do anything to the LEDs anyway, because the LED spotlights only need dimmed levels of power to operate at full power, so they stay at full power until the dimmer switch is almost at minimum, and extinguish at the same point as the halogens completely extinguish from dim.

Note, I bought the LED spotlights just to see what they are like, and I don't use my ceiling light fitting with the GU10 lamps all that often. The existing multicolour halogen lamps were only really accent lighting, not good enough for reading or anything, so I was replacing accent lighting with accent lighting. I still use my 20w halogen desk lamp for most of the time.


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PostPosted: Tue Dec 29, 2009 4:57 pm 
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I have some GU10 LEDs ( 20x 5mm LEDs) bulbs in the 2 "corridor" bits of my hall. Those are really only supplementary lights and there is a main light. They are supposed to be equivalent to "8w" whatever that means as there isn't an 8w halogen rating nor CFL. They are dimmer than a 7w CFL GU10.

My study uses 4 of these LEDs and is "bright enough" although it is a small room. 4x 7W CFL GU10s were really a bit of an overkill (but not as much as the 4x 50w halogen of the previous owners :shock: ). The LEDs aren't bright enough for task lighting say in a kitchen, but then again what do you expect for less than £2 each.

A bar is was in last week was entirely lit with the Luxeon 3 LED GU10s and each LEDs is (I think) 3w each. I hadn't noticed until I looked up that they were LEDs and the colour temp was as good as a halogen (unlike a £2 example). Those however are at least £20 a pop ( it's a while since I looked at the prices) so again you get what you pay for.

For low energy lighting, certainly at "domestic" prices, CFL still reigns supreme over LEDs. However LEDs are fab for Christmas tree lights! :D Much better colours than bulbs.


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PostPosted: Tue Dec 29, 2009 11:20 pm 
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Today I noticed a zebra crossing in Bispham which has belisha beacons lit by LED. The traditional beacons are of course what looks to me (I may be wrong) like an ordinary domestic bulb with a yellow globe round it. However these LED beacons are interesting as they have yellow LEDs on the outside of the fitting all around the edge of the globe and it's these lights that flash on and off, the main globe in the middle remains unlit, other than the backspill from the LEDs. It looks quite good and is certainly bright but is unusual to see just the ring around the globe being fully-lit. I suppose if they are rolled out across the borough that people will get used to them though.


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