How to specify an LED luminaire
Our responsibility as a reputable manufacturer is to ensure our products will perform over their lifetime to ensure that you, as a project designer, can specify a solution which won’t let you down. But with so many companies starting to offer LEDs as part of their ranges, what makes a good LED product?
The following summaries provides an overview of the technologies within and considerations regarding the specification of an LED luminaire.
i) THERMAL ENGINEERING – effective heat dissipation
The LED source has the potential to be a long life product so long as the junction temperature at the centre of the LED remains within set specifications. As an LED source is not equipped with enough material or surface area to dissipate heat away from the junction point, it must be bonded to another thermally conductive material, to diffuse this heat away.
As part of our design process, all acdc products are simulated through complex thermal management software to ensure the LED junction point will not exceed specified temperatures. Some products even utilise liquid cooling, whereby copper pipes are deployed within the heat sink to dissipate het quickly from fillings with a high concentration of LED’s.
All heat sinks can, and should, get warm. In fact, if a heat sink isn’t getting warm you have to question its purpose and effectiveness! Similarly, a heat sink shouldn’t be getting to ‘halogen’ sorts of temperatures where it is too hot to touch!
ii) LED SELECTION – not all LED’s are created equal
Today, there are many LED sources available, but the performance and quality of these products can vary dramatically, impacting seriously on the output and lifetime operation of the luminaire. acdc only work with the most reputable LED manufacturers, based in Europe and the USA. However, there are still significant differentials within these company’s ranges, which must be researched and tested before we incorporate them into our products. Obviously lifetime performance is critical, but several other key parameters are:
a) Light output has historically been specified using wattages i.e. 50 Watt halogen, which is unfortunately inappropriate when specifying LED’s. The lumen package and relative power consumption is the only way to ensure that the lighting performance you require, will be delivered. For example, there are several ‘1 Watt’ LED’s available from CREE, with a lumen choice of 40, 60 or 90 lumens! The performance difference (and price) is huge, so always remember to quote lumen packages when specifying your LED. acdc only work with the brightest LED sources available, and are one of the only manufacturers to produce photometric data for our products in line with LM79 testing, along with LED performance data sheets which are updated on a regular basis. Our approach is transparent, and enables designers to work with the latest technologies and information.
b) Colour temperature has historically tended to have a blue tinge with white LED’s, but in recent years excellent progress has been made in developing a much warmer range of colours, right down to 3000°k and even 2700°k. This has enabled forward thinking manufacturers to develop products which can replace traditional technologies such as halogen and metal halide with LED.
c) Colour binning is a term which refers to the process of grouping similar LED’s together in a ‘bin’ according to colour temperature. Typically an LED manufacturer will supply to a four step MacAdam Ellipse – as theoretically the human eye is not supposed to be able to detect anything less than 4 steps. In reality, however, especially when viewing warm white colours, it can. In short there is a noticeable, visible colour difference in LED colour, as supplied by the LED chip manufacturers. The prestigious nature of the projects which acdc work on, has driven us to develop a further colour selection system, “the acdc dual binning process”.
This process ensures binning to 2 MacAdam ellipses and a project based record is kept of each and every project we supplied by acdc for future additions or replacement.
WE GUARANTEE COLOUR CONSISTENCY ON EVERY PROJECT WE SUPPLY.
(d) Colour rendering is equally important, especially when substituting these traditional sources. Whereas lower grade of LED’s may have a lower CRI, making the subject appear grey or washed out, the best quality LED’s have CRI’s in excess of 90 CRI, delivering exceptional colour rendering across the spectrum.
iii) OPTICAL DESIGN – harnessing the light
Optics sit in the path of the light between source and target and as such have inherent losses. An optical system can never increase light output. Despite these losses, if used correctly, an optic can increase the apparent or effective efficiency of a luminaire by concentrating more of the light produced onto the desired location. A well designed and produced optic can see efficiencies of up to 90% whereas the same design poorly tooled or with lower quality materials could easily drop below 50%. At acdc we only use the highest quality optical grade optics from reputable manufacturers after several qualification and verification procedures.
iv) LUMINAIRE QUALITY & DESIGN – an opportunity for excellence in design
Whilst the technology on board a luminaire may be acceptable if the quality of design and manufacturer of the fitting can still seriously affect the lifetime performance of an installation. The design of acdc luminaires is focused on delivering the right lit effect, maximising the lighting performance and offering the designer the functionality they require for their application.
Equally important, however, are the quality of materials and the manufacture of the entire fitting. acdc products are genuinely the best quality LED lighting luminaires available and our product quality is world class.
v) LED DRIVERS – a wide ranging choice
LED’s need to be powered by special current regulation drivers and not the typical ‘low voltage’ transformers used for powering other traditional light sources. Whilst there are many different LED drivers available, we recommend sourcing both luminaires and drivers from acdc to ensure compatibility. acdc only use the most efficient drivers and offer a whole range of solutions, including several dimming types and IP rated versions.
vi) PRODUCT TESTING – independently certificated
We understand that when a specification is being drawn up, it is not only the name of the manufacturer which is on the line, but also that of the specifier themselves, a matter which is at the heart of the company’s philosophy. This is why we have constructed in-house test chambers for ingress protection and thermal performance for use both during the design process and testing beyond, ensuring that only luminaires of the highest quality will be supplied. In addition, all acdc products are independently tested.
vii) PHOTOMETRICALLY TESTED – independently verified
acdc guarantee superior lighting performance with all of our products. Each product’s specification sheet clearly states independently tested photometric data, which is tested in line with LM79 – this is the real output figure of the fitting that you would use for your calculations. This data includes the fittings efficacy, expected lifetime and lumen maintenance. This data can also be supplied downloaded from our website in IES format and is continuously updated in line with improving LED performance.