LED's are all the same, right?

One of the most popular points of discussion I have with Architects and Designers at the moment is “what makes some LED fittings better to spec than others” With the endless bombardment of product emails being sent to me and I am sure some of you, from all corners of the globe, including right here in Ontario, offering the best new LED luminaires, how do you decide what’s good and what’s not and then justify that choice to your clients?

     

To answer that we need to look at some basic facts. In LED chip buying, as in so many other facets of life, money talks. LED manufacturers like Cree, Xicato and Lumileds etc sort their LED chips into coded bins ranging from the premium chips to the low end chips based on industry criteria. The big players like the TV and PC manufacturers demand the very best LED’s and pay a premium to get them. Top end lighting manufacturers are also in a position to purchase from the higher end bins but as I am sure you can appreciate, the top rated LED’s are far fewer in number than the lower rated ones so price is higher and demand cannot always be met. The small independent companies have neither the influence or finances to play in that league so tend to buy mixed batches as these are cheaper and delivery time is quicker. Another key point to note is that as you go down the bin ratings, not only is colour temperature less consistent but lumen output decreases. The range is around 20% lumen drop from top bin to bottom bin.

   

 I guess at this point I should explain a bit more about the need for binning.

The human eye can detect very subtle changes in color, down to ~10 nm for red and 2–3 nm for green. For white light LEDs, this sensitivity may or may not be an issue depending on the application. For example, in applications like flashlights and headlamps matching the exact chromaticity of white light is not as critical as that of an application using a string of a dozen or so LED modules to light a wall in an office building. If the LEDs aren’t matched properly, they will produce a kind of rainbow of different shades of white light on wall. This problem doesn’t exist with an incandescent lamp since it produces a wide range of frequencies.

To minimize this potential problem, vendors provide binning charts such as this so the buyers know what they are getting.

 In 2008, ANSI and NEMA collaborated to establish a bin standard ANSI C78 377A1 which has become a minimum requirement for Energy Star® certification. This standard specifies a bin size that approximately correlates with the degree of color variation we experience today with commercial CFL sources. This allows for some degree of variation in color temperature among white light sources.

OK, so how does all this help you guys? Well, LED’s are available to any lighting manufacturer but the simple fact is that the stand alone LED lighting companies based here and abroad don’t have the research budgets of a Cooper or HE Williams size lighting company and in most cases have only been around for 1-2 years at most so don’t have the history of in depth testing and R&D behind them. Tests are often theoretical and installations few if any. They are also at the disadvantage of only producing a few LED luminaire lines so have to rely on those to keep the company afloat which is why they mostly buy from mixed bins to get the best price and quickest delivery. Offerings of 50’000-100’000hrs life from them is also a concern as many of the smaller companies will not be around in even half that time, voiding any warranty your client has. Another common issue is that if available, ies files are normally done from the chip manufacturer’s data. This data is taken from the top bin LED’s so real world results for luminaires using mixed binning could be up to 20% lower lumen output than the ies file suggests so your 50fc suddenly becomes 40fc when installed.

I know it’s a minefield out there for those wishing to specify LED but my advice is, if light levels, colour temperature consistency and longevity are important to you, choose manufacturers with a long history in lighting and a proven record with other lamp sources too. If you do use an LED only type line like i2 Systems, iLed or V2 etc, always ask about their choice of binning and remember that sometimes some LED luminaires are cheaper than others for a reason. As sustainability and energy conservation become more and more important, the bandwagon gets more and more populated with new LED lighting companies trying to cash in. Some are good, many are not so “buyer beware”. I am very picky about which LED manufacturers I use, I think you should be too.

Post by Jon Lewis