Neil Webb

No one in the lighting industry would deny that advancements in solid-state lighting technology move at lightning speed. To keep up with the new discoveries made in LED sources and LED luminaires, as well as the quantity of new products entering the market, industry standards such as the Illuminating Engineering Society's LM-79 and LM-80 have been created to establish a baseline by which LED fixtures can be evaluated. One of the principal avenues, as recognized by the lighting community, for evaluating products is the U.S. Department of Energy's (DOE) CALiPER program, which was started in 2006.

THE CALiPER PROCESS CALiPER tests a wide selection of solid-state lighting products intended for general-illumination purposes. The program tests products two times per year through qualified, independent testing laboratories. The tests are blind and the DOE makes the reports available to the public—for “non-commercial, educational purposes only.” Summary Reports provide a general overview of the test findings and are available on the DOE's SSL program website ( These reports do not list manufacturers; those are available in the Detailed Reports, which provide extensive data on the tested products and are provided to users who register on the DOE's SSL site and agree to follow the DOE's no-commercial-use policy. To date, more than 300 products have been tested.

The most recent CALiPER testing report—for Round 11 of testing—was released in October. It evaluated five types of fixtures and sources: arm-mounted roadway luminaires, post-top roadway luminaires, linear replacement lamps, high-bay luminaires, and small replacement lamps. The testing process occurred from March to September. To provide a benchmark for comparison, traditional lighting products that use incandescent, halogen, fluorescent, high-pressure sodium, pulse-start metal halide, or ceramic metal halide lamps were also tested and included in the report.

Compared to previous rounds, Round 11 showed that LED products continue to achieve greater efficacies, and manufacturer performance claims have become more accurate, although there is still room for improvement. Round 11 also found that even though the LED outdoor fixtures tested “matched or exceeded their benchmark counterparts in efficacy, most showed significant variations in color characteristics … and their distribution characteristics.” Lastly, although LED linear replacement lamps have shown improvement, performance questions remain when it comes to light distribution, color quality, and reliability.

LINEAR REPLACEMENT LAMP CONCERNS One product that has received particular scrutiny is the linear SSL replacement lamp, which varies in color quality and the methods used for dissipating heat from its tubular form. There is also concern about using linear SSL replacement lamps in recessed troffers for replacements or retrofits, specifically when it comes to how they are powered and connected to the electrical infrastructure. Troffers are usually powered by fluorescent ballasts that make contact at the ends of the lamp; the ballast is held in place by linear lamp-mounting brackets, also referred to as tombstones.

Manufacturers take different approaches to how they power linear SSL replacement lamps. Some use the fluorescent ballast, some use an onboard driver, and some replace the ballast with an external driver and rewire the tombstones—they mount and power the lamps with separate mounting brackets. In this last example lies the potential for trouble. By changing the assembly, which was designed for a fluorescent lamp-and-ballast relationship, there is the potential to compromise the UL listing as well as the possibility of creating unsafe electrical connections. As the CALiPER 11 report notes, “When the ballast is removed and replaced with a driver or with direct connection to 120VAC line voltage, the tombstones and associated wires are no longer operating as when wired for fluorescent lamps.”

To date, most SSL linear lamps require the removal of the troffer ballast, and then input voltage enters the lamp from the pins at one end and passes through to the other end. Some manufacturers provide wiring and installation diagrams so that the installer will know how to remove the ballast and rewire the LED lamp, but most do not provide clear instructions about the rewiring requirements. Related trade groups, as well as safety and standard organizations, have provided preliminary feedback to the DOE, and CALiPER is working with the National Electrical Manufacturers Association, the Canadian Standards Association, and Underwriters Laboratory to create clear, informative guides for the selection, purchase, and installation of SSL linear lamps.