LED lighting – it’s not just about the look

The only way is LED, it seems and estimates of its market penetration over the next 10 to 15 years range from 50 to 75% – so you need to keep ahead of the curve on this one as Andy Douglas, Managing Director of Timeguard explains.

A confusing array of new designs are introduced to the market every day and, now that we have a choice, it is time to start sorting the wheat from the chaff, and decide what questions to ask when specifying and buying LED lighting.

We all know that LEDs use semiconductor technology to convert electricity into light; and that they generate a different quality of light that has precluded them from the mainstream domestic and commercial market.  As with all technology, change is fast and now these lucrative applications are open to LEDs.  The possibilities are endless and the future will see brand new ideas coming to fruition. For now, though, what we see on the market tends to be traditional types of lights with LEDs used where filament or incandescent lamps went before – and we fall into the trap of judging them by the same criteria.

At Timeguard, we have resisted the temptation to simply put a bank of LED ‘dots’ in a traditional housing to take advantage of the market’s rose-tinted view of LEDs, and developed instead entirely new designs for our outdoor security/courtesy lights,  that optimise the technology and bring real, new ideas to the table.  Lenses ensure even, and diffused light, a complete rethink of the design and the lower heat output of LED’s enable a compact and attractive exterior design, honest measurement of output enables the market to see what they are getting and quality control guarantees value for money.

Specifying

The main advantage of LED’s is cited as their energy efficiency, but the quality of light emitted is important too, especially now the technology is being used in our homes and offices. You need to understand how to measure, or describe, the performance.

We all started out by quoting power ratings; 8W, 16W etc. These are numbers that everyone thinks they understand, but they do not tell the full story. Of more relevance than Wattage is the measure of Lumens (luminous flux), or the light perceived by the human eye.  Luminous efficacy, the measure of how well a light source produces visible light is then measured in Lumens per Watt. 

Even here you have to be a bit careful, because some products give the LED output and ignore the light loss in the fitting. Rest assured that the Timeguard Night Eye range quote a measure of lumens that is the output of the fitting, allowing for energy loss and absorption.  For instance, LED drivers are typically 85% efficient, which means that a measure of Lumens that does not allow for the whole fitting is giving a very false impression.

As well as the efficiency, important parameters of the LED driver are the power factor and reliability. A driver with a low power factor draws more current from the supply than one with a high power factor for the same amount of useful power used.  Electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor. LED driver reliability is also important, in many cases a poorly designed driver can be the limiting factor in the life of the fitting.

Old habits die hard and we will all still be tempted to think in Watts, and if this is going to drive your buying decision, then remember that power consumption is also a factor of the whole unit from the mains circuit connection to the tip of the diode, it is not the ‘rated wattage’ of the LED chip.

Another feature of light quality is photo-biological safety. The politically correct reason for ensuring this is that it confirms that the light presents no hazard to wildlife however users of outdoor lights may be more impressed that it means that their new light will not attract moths and midges in the way that traditional lights do.

Quality and user friendliness

LED’s use mains power to provide the correct DC voltage and current, and so an LED lamp requires a lot more than the diode;  there is also a driver and a heat sink, and the quality of these components is as important as that of the diode in building a long-lasting product. Checking for conformity with safety directives should be a given, of course!

For a pleasant lighting effect, there should also be optical lenses to modify the distribution of the light and as a rule of thumb if the dots that are the LEDs are not obscured by lenses, you may want to shop around some more before buying, as the lamp will not deliver a pleasant, diffused light.

The moral of all this is to take an overview of the performance, and look beyond the headline numbers because very cheap is rarely very cheerful.  The most economical lighting of all is the lighting made from quality components which can be fitted and forgotten, and that usually means a trusted brand name.

Switching

For indoor use too, LED’s call for a fundamental rethink. We have all become used to using PIR detectors to switch lights, but relatively few of the PIRs on the market are actually rated to switch LED’s which, despite their low rating, do generate a significant spike in switching.  That is why we made sure our enhanced PIR detectors were rated for LED’s when we introduced them early last year. At the time, LED use was still relatively low, but the writing was clearly on the wall.  

These ceiling and wall mounted PIR detectors brought affordable presence detection to the market, enhanced sensitive detection over a central 3m field, where they can react to the slightest movements of office or other sedentary occupants. In addition, they provide reliable motion detection over a full 10m field (based on a typical 3m ceiling height). With their 360 degree fields and simple time on and light level adjustments, they are set to become the new workhorse PIR detectors of choice for all energy saving applications.

Dimming

LEDs also present a bit of a conundrum when it comes to dimming.  The challenge is that where there is no agreed standard for LED drivers, few dimmers have been purposefully designed for LED lighting to date. 

This is where the KNX open protocol is stealing a march, because users and systems builders can freely download and use all of the latest dimming curves. KNX is a protocol that enables devices from over 200 manufacturers to be used together, affording maximum flexibility when choosing components for a system.  It is equally suitable for large projects like the Salford Quays redevelopment as it is for refurbishment of a single office unit or house, and it too is coming into the mainstream. In keeping with the open source ethos of KNX, compatible LED dimming actuators will be universal.

Showing the way is the Theben Universal Dimming Actuator that configures 2, 4 or 6 channels, with the option to add booster units for higher loads. It provides step-less dimming using optimised dimming curves included in the free KNX ETS configuration software, and new dimming curves can be imported as they become available.

What next?

This month sees Part L of the 2013 edition of the Building Regulations and as we went to press it was generally assumed that the metric for lighting energy will move to total consumed energy rather than luminaire-based performance, with LENI (Lighting Energy Numeric Indicator) as the tool for measurement.  It makes sense to me and will increase the drive to more efficient luminaires and lighting controls.

Let’s not forget, however, that the massive energy savings that LED lighting is offering in more and more applications means that consumption is not the only factor in choosing LED lighting – looks, build quality and the nature of t
he light emitted are high on the list as well.

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