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Not ‘Fit and Forget’

10 July 2009

LEDs are not - as many believe - a fit and forget option. Miles Pinniger unravels some of the common misconceptions and also sets out the applications where LEDs are making a positive contribution.

THE ADVANTAGES OVER TRADITIONAL LIGHT SOURCES THAT LEDs provide, such as lower energy
consumption, focused beams, longer life, improved robustness and smaller size, together with instant starting and easy dimming have contributed to their growing popularity. In many ways they have become an aspirational specification option for a wide variety of applications – in some cases before their time.

The problem here is that misunderstanding of the suitability of LEDs for certain applications instead leads to disappointment from the end user, often because they have been mis-specified in the first place. This is partly because there is no industry standard or code of practice for the specification and use of LEDs, or the design and quality of the LED lighting fittings that currently abound in the marketplace.

Because LEDs are electronic light sources, many are being produced by electronics companies instead of traditional lighting companies. This is both good and bad. Good because it encourages competition and a rapid rate of development. Bad, because a lot of mistakes are getting made at the end users’ expense. LEDs get built into structures – ceilings, floors, walls and pavements, and the consequential costs of changing or upgrading them can be very high.

Currently LEDs are not as efficient as modern T5 fluorescent tubes or ceramic metal halide lamps, so generally they are not yet a costeffective option for areas requiring high lighting levels like display lighting in shops or general lighting in offices. On the other hand there are some more specialised applications like
emergency escape lighting and freezer cabinet lighting where they already far excel the performance and reliability of previous solutions.

Sometimes they are being mistakenly specified in place of T5 fluorescent lighting or low voltage tungsten halogen lamps, with the result that the desired lighting performance and colour rendering is simply not yet achieved and disappointment results, but within 2-3 years it is likely that retail display lighting in shops and
downlighters in many applications will be LEDbased.

Another common problem is in exterior applications. They also perform badly under heat, and heat dissipation from the LED itself remains one of the key challenges in the development process – especially for interior fittings recessed into ceiling voids. However, it remains true to say that this electronic light source does have an increasingly relevant role to play in today’s lighting agenda, but like any product group, LEDs still have their limitations; they are not a ‘one size fits all’ option for those looking simply to reduce their lighting energy consumption and the message is definitely ‘proceed with caution’ and seek the
specialist guidance of an FM company with specialised lighting knowledge.

Thanks to their multiple advantages, LEDs are an ideal solution for potentially driving cost efficiency into lighting schemes where the clever use of light plays an important part in the overall perception of an organisation. When used for architectural lighting or signage they can create some wonderful effects with their beautifully saturated colours, and their suitability for rapid switching and dimming enables dramatic and dynamic scheme designs. The lower demand on battery power and the neatness with which they
can be installed makes LEDs an ideal consideration for emergency lighting applications – and anywhere where solar or stored power is the principal energy source.

Where high lighting levels are not required, good low level and ambient lighting can be achieved using LEDs. For example, hotel corridors, perimeter walls and architectural detailing can be illuminated with light from LEDs creating ambient pools or softly light washed surfaces.

The retail sector has responded to LEDs by using them to light the underside of display shelving. Freezer cabinets in many supermarkets are being refurbished with LEDs because they operate very well in cold.

Once specification has taken place and the lighting has been installed in a new or existing application, it falls to the FM or end user to understand and respond to any maintenance issues that may occur – and they will do. LEDs and their electronic drivers employ large numbers of discrete electronic components and
there will always be failures. At the moment no LED products from different manufacturers are interchangeable and because of the rapid rate of obsolescence and a plethora of obscure manufacturers, obtaining compatible spares and replacements is a potential minefield.

Some LED installations requiring very specific maintenance regimes. Without specialist help, costs can quickly spiral out of control, and without careful management of the design process, the initial reason for selecting LEDs over other forms of lighting or traditional light sources can be compromised. FMs need tounderstand lumen maintenance and mortality in similar terms to when dealing with conventional lamp technologies, but there are caveats. For FMs used to dealing with conventional lighting systems, there is little change in the level of light output until lamp failures occur. A planned preventative maintenance programme will avoid this risk and when the lighting levels fall below the specified minimum, relamping takes place.

On the other hand the light output of LEDs degrades gradually over time, but does not tend to fail as catastrophically, or as noticeably. In a large installation the effect of this light degradation may be to reduce the overall level below the design standard. The Alliance for Solid-State Illumination Systems and Technologies (ASSIST) has found that 70 percent lumen maintenance is close to the threshold atwhich the human eye can detect a reduction in light output. The research shows a 30 percent reduction in light output is acceptable to the majority of users for general lighting applications. However at this point, changing LEDs in an installation is likely to be complicated and expensive, with a strong likelihood that the original types are no longer available as replacements, and the whole installation may have to be replaced.

When the system begins to fail the lack of a coherent set of guidelines means that replacement carries its own problems – the risk is that replacement LEDs are not compatible with the existing lampholders or driver voltages. Using an outsourced specialist to take on this risk removes the cost for the organisation.
There are still solid-state lighting technologies emerging, including Organic LEDs (OLEDs), and improved
electronic controls to deliver increased efficiencies.

However, the commercial environment needs to consider LEDs as only one part of a range of emerging lighting methods to create the optimum solution for the end user. LEDs carry many advantages over
traditional forms of lighting for certain applications but LEDs are not a fit and forget option and never will be.
● Miles Pinniger, lighting advisor at Dalkia


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