Josue Oquendo

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 color 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, being 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.

When paired with legacy dimmers such as TRIACS, LED replacement lamps may experience performance issues due to incompatibility such as: “ghosting,” in which the LEDs continue to emit light after the control is off; flicker; and “popcorning,” in which individual diodes in a lamp turn on and off erratically.
Josue Oquendo When paired with legacy dimmers such as TRIACS, LED replacement lamps may experience performance issues due to incompatibility such as: “ghosting,” in which the LEDs continue to emit light after the control is off; flicker; and “popcorning,” in which individual diodes in a lamp turn on and off erratically.

An LED, however, stops emitting light the second that the power is cut. The resulting rapid on–off in illumination, or flicker, can be disorienting, nauseating, and even seizure-inducing.

Incompatible legacy systems can also cause “dropoff,” in which a light is dimmed to a certain point and then shuts off prematurely—or the opposite, in which a lamp intended to gradually brighten will suddenly “pop on.” “Ghosting” occurs when an LED persists in producing light even when the control is turned off, while “popcorning” describes the phenomenon when individual diodes in a lamp turn on or off erratically.

New challenges in compatibility are of particular concern in larger commercial and institutional projects where an LED luminaire becomes an integral component bundled into a larger lighting system. For example, some legacy controls need a minimal amount of power to perform properly, and an LED might not supply enough wattage, causing the controls to try to compensate with electrical power surges, resulting in uneven performance and shorter operating life spans.

The Lack of a Common Standard

One may expect that the physical incompatibilities between legacy systems and LED-specific controls will resolve as the former fade from use and the latter prevail. But this only leads us back to the problem of the absence of a universal standard among LED and lighting control manufacturers. In some ways, this is a more troubling issue.

Lighting and control manufacturers, industry associations, government agencies, and private and public research institutions have recently begun to seriously tackle the problem. There is no shortage of standards issued by the leading organizations in the industry, including NEMA, the IES, and the Institute of Electrical and Electronics Engineers (IEEE), in an attempt to align LED manufacturers and the lighting industry toward a set of universal standards.

Some standards cover component issues, like NEMA’s SSL 7a: Phase-Cut Dimming for Solid State Lighting—Basic Compatibility, which governs the interaction between lamps and dimmers. Others are technology-centric, like the ZigBee Alliance’s “ZigBee Light Link” and the EnOcean Alliance’s Wireless Standard ISO/IEC 14543-3-10, both of which focus on wireless controls, and the Zhaga Consortium’s Zhaga Interface Specifications, which apply to LED light engines and components. Standards can also target the end user; later this year, NEMA expects to release a labeling protocol to make it easier for specifiers to match compatible lamps and controls, says NEMA spokesperson Tracy Cullen.

But confusion among manufacturers and lighting designers, as well as consumers, remains: Which standards are mandated and which are recommended? Some standards, such as NEMA’s, are enforced by state and federal agencies, like the DOE through its Energy Star program. Still others, like those issued by the Zhaga Consortium and the EnOcean Alliance, are optional—though the organizations hope that so many manufacturers will use them that they will become a de facto requirement.

The primary hurdle with all of these standards, thus far, has been adoption. Most manufacturers worry that pruning their product offerings to meet a common standard will mean sacrificing a promising proprietary feature. And no one wants to see shelves stocked with identical products. “Manufacturers want to maintain their differentiation, and consumers want differentiated features,” Biery says.

Raising the Bar

The lack of consistent component compatibility and universal standards does not bode well for lighting designers or end users. But treating a lighting system as a critical capital investment is the first step to initiating change. Luminaires and lamps must be recognized for the sophisticated electronic devices that they have become and, consequently, as long-term building-system investments, not simply as products. Understanding the difference opens the door to a wealth of opportunities in energy savings, comfort, and design.

But it also means that architects and lighting designers need to be knowledgeable about their lighting options, and be ready to specify standards and products that they know to be compatible. Naomi Miller, PNNL senior lighting engineer, says that the sort of compromises that, unfortunately, lighting designers have become used to making—say, settling for a lesser lighting control system if a contractor says the specified choice is too costly—can now have long-term consequences in this era of LEDs, in the form of dimming issues or even premature failure.

Compounding the issue is the time lag between product specification and actual installation, a period that can take several years on architectural projects. “LED drivers are advancing at the rate of consumer electronics,” Biery says. An entire generation of advancements can come and go within a few years, so a client may not get the benefit of a state-of-the-art lighting offering. Or, Miller points out, a product specified two years ago may simply no longer exist. This means that architects need to have a lighting designer on staff or as part of their project team. It’s the only way to keep pace with the technology changes.

The lighting industry is well aware of the complexities that result from compatibility issues. This year, we may see the introduction of near-comprehensive standards, if not their adoption by industry and government organizations, says Andrew Bierman, a senior research scientist at the Lighting Research Center, in Troy, N.Y.

In fact, California recently announced that, starting in 2017, it would require all LEDs sold in the state to comply with NEMA standards. The DOE’s Energy Star program already requires manufacturers to publish compatibility specifications for their LED components if they are to receive its seal of approval. And the influence of local governments and federal initiatives like these cannot be underestimated: The DOE’s Next Generation Luminaires Design Competition, launched in 2008, has played a significant role in advancing LED luminaire and lamp product offerings.

As the dust settles among the bevy of industry standards available, the long-term solution needs to with a change in mind-set among all constituents of the lighting industry. Just as one wouldn’t expect an Apple keyboard to work perfectly with a PC, people can’t expect LEDs to work with any old control systems, particularly when the industry is still a long way from mature LED technologies.


“Controlling LEDs,” a technical white paper by Lutron, 2014. Available at:

ASSIST recommends publications by the Alliance for Solid-State Illumination Systems and Technologies and the Lighting Research Center, 2015. Available at:

Zhaga Interface Specifications (Books), by the Zhaga Consortium, 2016. Available at:

SSL 7a-2015: Phase-Cut Dimming for Solid State Lighting—Basic Compatibility, by the National Electrical Manufacturers Association, 2015. Available at: