The open areas of our works are floodlit. Originally incandescent, then tungsten and now metal halide. We use 150w, 250w & 400w mh lamps. All on 9m stands and operated by dusk/dawn sensors. Some of these lamps are now again degraded. I am thinking that these metal halides would 'roughly' equate to 500, 750 and 1000w tungsten lamps. Thinking of converting to led. Not for greenery but for (1) reduced running cost and (2) ease of replacement as I'm the one one that maintains them. Never have had much fondness of heights. I haven't a clue as to what size led replacements I might be looking for and would appreciate help on this.
The 400watters could be replaced by 2x 200/250w (MH-led) equivalents. This might prove a bonus in terms of better coverage.
Any thoughts please on led output comparisons and perhaps suppliers of suitable luminaires? Thanks, Nick.
You'd need to read several articles in that category to answer the q. Light output is covered by lumens, CCT and CRI, the latter explained in the fluorescent article.
That's probably not far off (although when you get to 1000W mains filament lamps, they are significantly more efficient than 100W and lower lamps).
To a first approximation, look at the lumen output figures for the different lamps.
One important thing this doesn't take into account are the losses in the luminare. Yours probably have reflectors to redirect most of the light out of the front, but these are never 100% efficient (or anywhere close). This is where LEDs have an advantage as they are implicitly directional (to varying degrees), so don't tend to lose as much light inside the luminare.
Another important area is what proportion of the light is directed where you need it, and how much is lost in spillage over areas you don't need (or want) to light up. Again, because of the much smaller light source in LEDs, it's possible to focus the beam much more accurately so more of the light is directed where it's needed and less wasted.
LED streetlighting downsides - they currently seem to be significantly less reliable than they should be. This may be because many companies have entered this area with little experience in producing electronics for outdoor street furniture. I've seen a number of local authorities install and then give up on LED streetlighting, when they turn out not to live up to their longevity claims. Some of the manufacturers have responded to this by guaranteeing to replace their products (including doing the on-site installation) if they fail, although that's not practical in all cases (e.g. a motorway where planning and night time lane closures need to be put in place, at vastly more cost than the luminare replacement itself).
I would wait a bit if you can - I think the LED products will rapidly get better as more local authorites try to roll out LED lighting, and the less reliable products naturally disappear from the marketplace.
And only 10 years ago CFLs for household lighting was going to save the world:-)
Care to name and shame? At least the LED lights I fitted at Collingham train station car park can be lowered to allow the LED head to be changed if it fails.
Yes, it's always sensible to make your own _independent_ comparisons between the old (reference lamp type) and the new "Wizz Bang" replacement that purports to be a power saving equivilent.
If you're comparing an existing lamp (or lamp type) against your latest purchase, you can use a P&S digital camera to gain some numeric data. The usual method is to set the camera to aperture priority and take a picture of the area of interest lit primarily by your lamp source(s), ideally with little to no light pollution from other sources.
Generally, most digital cameras can select a finer increment in selected shutter speeds than they can for aperture settings. If it turns out that the camera chooses the same exposure values, you can compare each picture to detect which, if any, was just marginally the brightest of the two.
For example, when I purchased an 810 Lumen 12W LED lamp from Asda a few weeks back for the princely sum of £3.49 to replace the LES 20W CFL in the adjustable pendant fitting above the dining table in our kitchen diner, I was able to note that the LED lit scene looked just that little bit brighter when the exposures chosen by the camera had been exactly the same in both cases.
Using the digital camera removed the element of guesswork in trying to rely upon direct observation alone to determine whether or not I was losing out on illumination levels in switching to the lower wattage LED lamp.
Unless you need to collect actual illumination data to a specific accuracy of measurement, there's no real benefit to be gained in spending money on a light meter when simply comparing different lamp types against each other using a digital camera will tell you all you really need to know.
I saw the smiley but Andrew was referring to the fact that a low pressure mercury vapor discharge fluorescent tube starts off at around a 110% of its 'design lumens' before swiftly dropping down to 100% during the first thousand hours or so of an 8 to 16 thousand hour design life when the output will have dropped to something like 80% before the drop is considered to be end of life.
The light output plotted against time follows an exponential curve where most of the initial drop to 105% takes place in the first hundred hours or so. The mechanism for the loss of efficacy in such lamps, istr, is largely to do with mercury argon 'poisening' of the fluorescent coating.
White LED lamps which use a blue LED to excite the phosphor coating must also suffer some loss of efficacy in the flourescent material used but, with lifetime ratings typically in the 30 to 50 thousand hour range, the rate at which the efficacy of the phosphor coating drops must be far lower than in the case of a mercury vapour fluorescent, presumably on account of the lack of such a 'poisening' mechanism.
Yeah, fluorescent lamps as described above.
That's true enough. I think the least effected by ageing during their rated lifetimes are the standard gas filled tungsten filament lamps, particularly when burning 'cap up' in pendant fittings.
I haven't seen any lifetime light output plots for phosphor coated blue LED lamps but I assume these are also based on the 80% of design lumens end of life criterium.
When I did my comparison test using a digital camera, comparing a 12W LED against an existing 20W CFL, I felt pretty confident that the CFL had only clocked up 1 or 2 thousand hours so was within a percent or two of its design lumen output. I took care to allow the lamp to thoroughly warm up to its final steady state operating temperature (10 minutes or so warm up time). The only "unknown" in this case being how much brighter than design lumens a factor, if any, applies to such LED lamps.
Since the old CFL has been put to one side, I can repeat the comparison say every 6 months or so and look for such an initial lumen efficacy drop mechanism in the LED lamp (the unused CFL should provide a constant reference source to ensure meaningful results).
Another thing to bear in mind with modern LED lamps (apart from the effect of colour temperature on the efficacy of its lumen ouptut rating) is the tungsten filament lamp type used as the comparison reference.
For example, you may see them compared to a "60W 810 lumen" tungsten filament lamp. This is only true for the American 117v 750 hour rated incandescent GLS lamp which is equivilent to a 75W 1000 hour 240v tungsten filament GLS lamp, not a commonly available lamp size here in the UK.
As it happens for once, a difference that makes the efficiency improvement of LED based lamps over the 220 and 240 volt tungsten filament GLS lamps used here and in Europe even greater than that experienced by our Yankee cousins. :-)
Very true. However, my limited experience of mains LEDs is they never get anywhere near their claimed life before failing. And they are more costly than a CFL.
That's very true in regard to their regular pricing. My experience is probably a lot more limited than yours in regard to lamp life.
I've only bought two during the past year, a 5W 270 Lumen BC 'classic' shape 'bulb' for a fiver last year and a 12W 810 Lumen 'bulb' for £3.49 earlier this month, both from our local Asda Superstore as it happened.
I suspect the 12W lamp has already clocked more hours than the 5W lamp simply because I eventually installed it in the basement landing area in a ceiling batten fitting just by the electric meter where it probably never sees more than half an hour's use per week on average.
Since that 5 watter is operating in the coolest part of the house, unencumbered by any form of lamp shade, it stands the best chance of living up to the maker's 25,000 hour life rating claim. At the current usage rate, there's every chance I'll be dead and cremated before it's clocked its first thousand hours. Even if I decide to leave it running
24/7, it's going to take nearly 3 years before it reaches the 25000 hour mark.
The 12W lamp, otoh, is probably going to average 4 to 6 hours a day, roughly 6 months per 1000 hours of lamp life. Assuming 2000 hours a year usage, that's a 12 year lifetime based on a 25000 hour life rating.
Thus far, I've not experienced any premature mains voltage LED lamp failures (but it's _very_ early days and a sample size of only two lamps).
Let's face it, with such extended life claims, any failures within 2 years of purchase are a guaranteed indicator for premature failure even if the lamps in question where left permanently lit after being installed.
Only this afternoon, I was in the "Home Bargain" shop with the missus, contemplating increasing the sample size to 3. I was looking at a 7W 620 lumen BC example they had on the shelf for £4.99 (same efficiency level as the 15 quid 810 lumen 10W LES lamp in our local Asda superstore).
In the end, I resisted the temptation based on my feeling that I would be joining the "Early Adopters'" club and paying a premium price for the priviledge.
A year ago, I would have snapped it up (and the other remaining BC example out of a pile of LES lamps) at that price but, ever since purchasing that 12W 810 Lumen lamp at the beginning of the month in Asda for a 'mere £3.49', my LED lamp bargain price point reference has now slid down to a new low.
I'm older and wise enough to know better than to play that game of "Early Adoption" to start over-investing in an immature technology that still has a few more years to go before it hits the limits on efficacy and mass production led pricing levels. I've still got an ample supply of CFL 'spares' to see me through the next couple of years so I can afford to play the waiting game. :-)
However, that won't stop me being on the look out for more LED Lamp Bargains. It's one thing to blow 3 or 4 quid on a single LED bulb but another one entirely when it comes to replacing the ten 7W SES CFL candle lamps in our two chandeliers at a price of £3.99 each to the tune of 10p shy of a 40 quid investment in the 7W LEDs currently on the shelves of Home Bargain.
I've no doubt that in a years time I'll be seeing 5W versions of equal or higher brightness SES candle lamps a quid or two cheaper. Others might argue, as they often have with computer technology, that there'll always be a better value product on the horizon and you face the risk of your purchase becoming dated or worse still, obsoleted no matter how much you delay. That's a valid argument for Personal Computers and all the spin off technoligies (smartphones, tablets etc) but not so for something like a more efficient lamp which has definite and well defined limits on its performance.
From the press releases issued early this year by Philips and Cree we can expect to finally see real product on the shelves in another 12 months time with triple the efficiency of the CFL (or only double that of an electronically ballasted linear fluorescent tube) at which point the manufacturers will be well and truly into 'Diminishing Returns' territory.
Next year's "Early Adopters" are not going to have their smug smiles of satisfaction wiped off their faces as swiftly as today's early adopters when the next round of lighting technology development makes its appearance.
I reckon that in about 12 months time, we'll have reached that point where the returns on running costs will finally justify the capital investment in LEDs with a very much reduced obsolescence risk factor to boot.
There will no doubt be better lamps available in the years succeeding next but the improvements will be more marginal than we know is the case today. Furthermore, the pace of such improvement will be slowed right down to a snail's pace compared to what we've witnessed during the last 5 years or so (and promised over the next 12 months).
By all means, snap up those odd bargains you might see from time to time where you know exactly where you're going to usurp an existing CFL or even an incandescent lamp to maximum benefit (but I'd hold off on a mass LED upgrade for another 12 months if I was you).
Incidently, it's just occurred to me that your problem of premature lamp failure could be due to overheating. Unlike tungsten filament lamps that can and do run at 200 degrees and higher temperatures in conventional lamp fittings which allows them to dissipate their 60 watts of waste heat with ease, LEDS are limited to a much lower maximum temperature (80 to 120 deg C ?) and can overheat in poorly ventillated fittings rated for 40 and 60 watt incandescent GLS lamps, especially when the lamp is burning cap up.
It's a limitation that's not so apparent when the lamp is quite obviously meant to be a "Drop In" replacement for the good old fashioned tungsten lamp. The thing to look out for is a lack of ventillation such as happens with some lamp shades and pendant fittings. Such fittings result in a nice cosy blanket of hot air surrounding the base of the lamp where the electronic ballast components live (or die).
The later more efficient lamps will be less prone to this overheating hazard since they generate less waste heat per lumen of output. This is one of the main factors that limited the earlier lamps to quite modest lumen ratings. It's only now that we're starting to see lamps with more useful outputs of 810 (and even higher) lumens (60W American / 75W UK GLS filament lamp types). This yet another good reason to hang back before 'blowing your wad' on a whole house relamping upgrade.
Although I've bought a few LED lamps (up until a week ago, 7. They're for places where CFLs aren't too good: desk lights (CFLs too heavy), long-use lights where output isn't important and 2 outside where CFLs take too long to warm up) I've been holding off until at least the 5050 etc. sizes have gone.
In a small room (about 2x3m) there was an 11W cfl in a quite translucent glass shade; it was good and bright and gave plenty of light, but I did, of course, cast a shadow everywhere I wanted to see.
Taking into account the need for at least some spread at source, I bought a
3-armed fitting in a bronze(y) finish (I hate chrome plate), deliberately choosing one that takes SES (E14) rather than the more common G9. The horizontal lampholders avoid the dark area of LEDs (and CFLs) being up to the ceiling and mean that the base of the lamps don't get so hot.
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Fortunately the tool provided for fitting the shades' retaining rings also handles the lamps.
Now, I'd sort of picked the lamps first. I was looking for >80lm/W output and a design that spread both the light and the heat. Found these little beasties:
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so 9W of LED at (nominally) 960lm total - rather better than the 880lm of a good CFL initially.
BTW, these look good also:
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A couple of days ago there were som 6W 720lm in the same format but they seem to have gone out.
Although the shades are a bit less translucent than I'd like them to be, the output seems a lot better than the 11W CFL and of course no warm up.
I have several places where the CFL is overpowered so that I don't have to wait and see.
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