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LED’s - Fade Away, Don’t Radiate

September 26, 2019

I was recently reminded that customers may not always get what they had originally expected!

How long do you think these “browned out” LED panels have been installed?

These panels have served just 12-15,000 hours, they are about 2 ½ years old!!

As you can see – the panels in this installation now exhibit a rather lovely brown patch across two thirds of their diffuser, dramatically reducing the effective radiation of light output. It would appear that sometimes poor combinations of technologies can limit progress, here we seem to be sinking back to the dark ages – when we thought inefficient lighting was fluorescent “troffer packs” and yellowing non-UV stable polystyrene diffusers!

Well, yes – maybe we are taking two steps forward and one step back; maybe the buyer didn’t notice his “bargain” luminaires might include a poor combination of diffusers, perhaps a light guide of a less than desirable material. Worse still, in some places you can now see which ones have been installed in a different orientation. Luckily they have separate standalone emergency lighting so the depreciation does not affect life safety systems. Oh– and it would appear that most of the LED’s themselves haven’t yet failed(what does that warranty say?)

LED Panel users beware – consider these lighting engineering facts before you select luminaires….

  • LED lifetime claims are not the same as “Luminaire Maintenance Factor” or Maintained Illuminance throughout the design lifecycle of a lighting installation – read the SLL Lighting Handbook; “Maintenance” section (Chapter 32, Page 417 – 425)
  • Lighting a diffuser from its edge means the light has to travel 100 times further through the material, ie about 300mm from either side rather than through 3mm when back lit, so depreciation is greatly exaggerated!
  • Light has to transfer from one material to other(s) in order to emit downwards as useful light – reliant on good contact through life with no distortion or deterioration?
  • LED’s have to be in good contact with the (heat insulating) edge lit plastic throughout life
  • “LED’s emit no UV”? – well maybe the blue light near the UV spectrum, or the increased temperatures due to light source contact may degrade many plastics?
  • Unitary Construction – you can no longer replace just the light source, reflector, or diffuser – having chosen a Flat Panel LED to save money on day 1, he’s now got to effectively throw away the whole luminaire – it can be “so – called - recycled” - but only by grinding it up as mixed waste and downcycling it to use as some sort of low-tech bulk filler material.

What could a user gain by using a different style of luminaire?

ie-  back – lit construction rather than a flat panel :-

  • Improved system efficiency Llm/W (Luminaire Lumens per Watt) from day one
  • Dramatically Improved the longevity & aesthetics of the luminaire and the installation
  • Reduced lifetime maintenance costs
  • Made best use of scarce materials, resources & minimised waste (fully serviceable, compatible with the Circular Economy)
  • Paid the same for installation & control system
  • Paid a little more for the luminaire product
  • Paid much less through life
  • Not had to go back to management and ask for more money to replace what was initially thought a quick win “no brainer” installation of low-cost LED lights!

Call Llumarlite if you’d like our help with a pocket and environmentally friendly competitive through life lighting solution, together we can help you select the right solution to minimise your operating costs and maximise benefits!

Links –

The “SLL Lighting Handbook 2018” is available to download free to CIBSE / SLL Members: - Here Publisher CIBSE, Product Code LH2018, ISBN   9781912034413

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