Seeking Compatibility in the LED Era

LEDs now illuminate everything from living rooms to roadways. But, as most lighting designers know, the technology comes with a distinct set of performance problems, stemming from its compatibility—or, more accurately, its lack thereof—with fixture components and controls from both legacy and solid-state lighting manufacturers.

In recent years, industry organizations such as the National Electrical Manufacturers Association (NEMA) and the Illuminating Engineering Society (IES), along with government institutions such as the U.S. Department of Energy (DOE) and the Pacific Northwest National Laboratory (PNNL), have been working to introduce a range of guidelines and best practices to market. Manufacturers, too, are playing their part, forming groups such as the Zhaga Consortium to participate in the development of industry protocols. But so far, the industry has been slow to adopt them, and no single set of comprehensive guidelines outlined by a professional lighting body, such as the IES (the principal entity to which the lighting community looks for technical standards), has yet to cover all the bases, in part because LED technology is continuously changing.

“There are lots of manufacturers and no generic standards,” says Bill Simoni, vice president for product management and business development at the New York office of global lighting manufacturer Zumtobel. He likens it to the early days of video cassette recorders: “People didn’t know whether to use Betamax or VHS.” As a result, designers are left with a confusing array of choices as they develop a project’s lighting specifications.

Physical Differences

The absence of an accepted standard in the rapidly changing LED market is only one aspect of problems surrounding the issue of compatibility. The transition from conventional to solid-state lighting products is another. To most, particularly when it comes to consumers, an LED replacement lamp is simply a chunkier version of the classic Edison incandescent, with its round head and screw-in base. Look inside, though, and the two couldn’t be more different. An incandescent lamp creates light through electrical resistance and a glowing filament, while a diode emits light when electricity passes from one semiconducting element to another.

LEDs, which don’t rely on a filament, can last for tens of thousands of hours longer than their counterpart legacy sources. The wrinkle is that LEDs can’t run directly off the electrical main—they need a driver, typically housed in the fixture base, to convert alternating current into direct current. This has its advantages: The driver, in coordination with a controls package, allows the LEDs to have features such as precision dimming and choreographed colour changes.

But it also can create new problems. Currently, most LED lamps and luminaires are being paired with legacy control systems, with dimmer switches, in particular, is a known troublemaker. “There is not an industry standard, and not even a generally accepted definition, on what the word ‘dimmable’ means,” says Ethan Biery, a design and development leader at Lutron. The vast majority of legacy dimmers are triode alternating current switches, or TRIACs, which work by interrupting the electrical current during its cycle. Because filament lamps continue to glow, albeit briefly, after the power is cut, the human eye doesn’t register a TRIAC’s effects, but only the overall reduction in light level, or dimming.