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LED lighting: not just a pretty place

LED technology offers major advantages as a light source and is rapidly becoming the light source of the future, but there are some pitfalls to avoid. Leighton James, product marketing manager at Cooper Lighting and Safety discusses.

LED lighting: not just a pretty place

There is no doubt that LED technology has much to offer, but, as happens with any rapidly evolving technology, there are some inferior fittings on the market, and contractors need to be aware that such products may not actually deliver all the benefits they promise.

A fundamental point to understand is that there is more than one type of LED used in light fittings. While the 5mm indicator types were used by some manufacturers in early commercial fittings, these are now being replaced by high-output (HO) LEDs, for the simple reason that the HO LEDs offer far superior lumen maintenance. After 6000 hours, the output of a 5mm LED drops to 50% of its original value, whereas the HO LEDs drop by only 5%. In other words, the HO LEDs will last for 10 years or more, but the cheaper 5mm LEDs will grow dim after just 2 years. Consequently, the 5mm LEDs are now predominantly used in fittings for the domestic market.

The HO LEDs offer the additional advantage that they can be integrated with different optical components, allowing a variety of beam angles and other effects to be produced. However, despite its rapid progress and development, the requirement of an optical lens to control its light means the HO LED is difficult to integrate into the format required for general illumination.

The arrival of the Multi-die LED helped address these integration restrictions. Unlike conventional HO LEDs, this technology incorporates multiple LEDs in a single package, giving increased light output in a smaller space and a wider spread of light.

High-output and Multi-die LEDs will maintain over 70% of their initial light output for at least 50,000 hours (typically 10 years’ commercial use), compared with around 12,000 hours for traditional fluorescent sources and 5000 hours for halogen lamps. However, maximising this operational life is dependent on effective thermal management and accurate drive-current control.

LEDs do not generate heat from the front, but from the rear, and heatsinking is required to keep the junction temperature down. For this reason, light fittings must be specifically designed to accommodate LED components. If LEDs are merely clustered together into an existing fitting that was originally designed for a traditional light source, they will simply overheat and deteriorate within a couple of years. But this is exactly the approach that has been taken by some manufacturers at the lower end of the market, so contractors should be very wary of just using the cheapest LED fittings available.

LED technology already has a proven track record of high reliability as it has been used successfully for a number of years in emergency-lighting applications. Essentially, this reliability stems from the fact that LEDs are solid-state devices, which have no moving parts and are not subject to component ruptures, breaks or leaks. As long as LED fittings use quality components from a reputable source and are designed and manufactured correctly, they will provide completely reliable service for many years without requiring any maintenance at all.

And when the LEDs do eventually near the end of their life, they will not suddenly fail like conventional light sources, but just get gradually dimmer, thereby providing a safer lit environment.

Since they are maintenance-free, LED fittings are ideal for applications where lamp replacement has traditionally been problematic - for example, wherever access is difficult because fittings are submerged or installed at high level. The traditional in-ground luminaire is also a good example: although access is straightforward, if the IP seals on these luminaires are not re-seated correctly after a lamp has been replaced, the result is condensation on the inside of the glass and possible failure of the fitting itself. LED versions overcome these problems because they completely eliminate the need for lamp replacements.

Another major benefit of LED technology is its energy efficiency. Climate change is firmly at the top of the political agenda, and as lighting accounts for a major proportion of the electricity consumption in a typical building, any improvement in the efficiency of the light sources used will have a significant impact on efforts to save energy.

Perhaps the one application most generally associated with LED technology is coloured lighting. Light from different coloured LEDs can be combined to generate any colour in the spectrum for either fixed or dynamically changing illumination and as the colour is generated at source, there is no need for filters which absorb the light.

Although LED technology is capable of producing exciting coloured lighting effects for discos or trendy bars, these will probably not be appropriate in most commercial applications.

However, in many workplaces, there is scope for smooth, slow colour changes, which can help to create a comfortable, pleasing environment. Furthermore, LED technology can be used to vary the shades of white light within a building. For example, in a hotel in winter, a warm white would create a cosy and inviting ambience, whereas in the summer a cooler shade might be more welcome.

Due to their compact design, LEDs can be discreetly integrated into building fixtures or furniture to create new architectural and display lighting applications, sometimes with the light source hidden from view. Popular examples include LEDs integrated into architrave, coving and counter trims.

Although LED technology is widely associated with emergency lighting and the dynamic coloured effects created in discos and bars, it now offers several major benefits in commercial lighting applications. The demand for LED-based lighting looks set for rapid growth as LED efficacy levels steadily rise and as building operators become increasingly aware of the potential savings in time, money and energy.

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