Saturday, 11 May 2013

How can I tell if LEDs in a light, tube or bulb will last a long time?
 
So the shop claims an LED light will last over ten years, or maybe 50,000 hours plus?
How can you tell how long LEDs are likely to last?
LEDs are not like modern fluorescent lighting - heat is their enemy.

You can be the detective.

You can start by thinking like of an LED like a living creature - they get warm when they work hard (making light),   ...if they get TOO hot they'll get worn-out soon.
Remember, LEDs visibly decrease in brightness as they deteriorate, so their 'life expectancy' is not the full story...

Look to see if there's anything else near the LEDs that will make me the LEDs even hotter.
Commercial LED-lights need a transformer to convert mains-power to the voltage LEDs can use, and that creates heat too.
Where is the transformer?
Is it in the same small 'space' as the LEDs making the LEDs hotter?

If the driver and transformer were inside this tube, the LEDs could overheat and fail soon
...or is it in a separate housing that can release heat to the air, connected by a wire to the LED-unit?
The same LEDs can last longer if the transformer is kept separate so there is less heat around them.
Most types of LED lights (including LED-tubes) are available with independent transformers if you look for the right supplier.


LED Light with large finned heatsink, and independent matched driver to keep mains heat away from LEDs (rear)
See how the designer plans to allow the LEDs to stay cool.EG. Are the LEDs mounted on a metal finned 'heatskink' which draws the heat from the LEDs and allows air to pass through the fins drawing the heat away?
There are good and bad heatsinks of course - the more fins and surface-area usually the better. Also LEDs of over 70 Watts benefit from other ways to conduct heat than just aluminium, starting with copper-pillars within the aluminium to bring the heat away from the LED faster.

 
 
How high is the total LED power?
As you can imagine, more power = more heat, so a single 1-Watt LED might survive for years with just a 1 cubic cm aluminium heatsink, but with a small heatsink a single 150W LED-source (eg industrial LED high-bay lighting) definately won't - the best examples of these use other cooling methods such as condensing or liquid-cooled systems.
As this is expensive, another solution is to fit more lights but reduce the power of each.  Two 75Watt LED lights with a single LED chip or "array" on a basic 'finned' heatsinks are likely to last longer on average than 150Watt light of similar design.

Instead of a single powerful LED light-source, some LED lights deal with the cooling challenge by using many low-powered LEDs spread across a much wider cooling surface. For example we make
LED light-fittings which replace ageing compact '2D' circular ceiling-lights. These have a metal body, with up to 50 small LEDs mounted across it:
Multiple LEDs on large heatsink for cooling=long life
 
 Cover should not prevent air getting to metal body

Would buying big-brand lighting assure long life?

Unfortunately, many 'high-street' names now make LED lights, but a lot are built down to a price, aiming to leave profit for their big infrastructure and advertising budget, and aimed at the domestic market where it's expected the bulbs won't be used many hours a week (maybe three hours a day in a bathroom compared to 24/7 in a hotel washroom).
Next time you're in a supermarket or DIY-shop spot the 'big brand' LED-bulbs or ceiling-lights with no heatsink at all, just moulded plastic which has almost no cooling ability but costs a fraction of what graded aluminium does??

 
 Professional-use 'long-life' LED bulb with deep finned aluminium heatsink

So it's usually better to find an expereinced supplier who already works with the sector you're in and understands the impacts created by the way you'll be using the bulbs. Picking a supplier who's worked under many Carbon Trust or Salix funded commercial schemes over many years is a good reassurance.

www.energyatwork.co.uk

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These are just my tips based on experience as a lighting enthusiast surveying sites and speccing energy-saving lighting in hundreds of buildings over ten years, and I know other people will have had different experiences (maybe different products and technologies too) so please feel free to share your own experiences here.