As a digital replacement for their fluorescent counterparts, linear or tubular LEDs (TLEDs) are winning favor. According to the National Electrical Manufacturers Association (NEMA), 6.9 percent of lighting shipments in the first quarter of 2016 were TLEDs, marking their first appearance in the organization’s market-penetration tracking. TLEDs may not supersede fluorescent lighting today, but they are establishing themselves as a competitive alternative.


In the past three years, continued performance gains and lower prices have helped TLEDs move beyond first-adopter lighting. Another indicator of growth can be found in the U.S. Department of Energy’s (DOE) LED Lighting Facts. The program showcases LED lighting products from manufacturers that voluntarily share the results of product testing using the Illuminating Engineering Society of North America (IES) LM-79-08. As of June 17, 2016, there were 4,523 linear LED lamps (TLEDs) listed by LED Lighting Facts, which is slightly more than 10 percent of the total products included. The lighting industry is clearly in the TLED game, offering products in T4, T5, T8 and T12 sizes.


While the information found in Lighting Facts is valuable, the DOE’s CALiPER program goes one step further conducting third-party testing of LEDs.


A June 2016 CALiPER report shared results of its follow-up TLED testing. Instead of measuring performance through demo installations as it did in 2013 (for more, see “Totally Tubular: Linear LEDs”), lamps were analyzed in the Pacific Northwest National Laboratory (PNNL) labs in Richland, Wash. 


In testing, 97 percent of the TLEDs offered a power factor of 0.90 or greater. Their luminous efficacy averaged 101 lumens per watt (LPW), representing a 10 LPW gain from 2012 to 2015 and an additional 6 LPW gain in 2016. These results placed TLEDs in the range of a bare linear fluorescent lamp and met the threshold for the DesignLights Consortium (DLC) Qualified Products List. That program requires TLEDs to have a color rendering index of at least 80 and a nominal correlated color temperature of less than 5,000K. About 97 percent of the currently listed TLED products meet both criteria.


Interestingly, the most efficacious LED product currently listed by Lighting Facts is a TLED at 190 LPW. Testing revealed that as lamp numbers increased (two- or three-lamp troffer) luminaire efficiency was slightly reduced.


The system as a whole


The CALiPER report states, “When evaluating TLEDs, it is critical to examine the expected performance of the complete lamp and luminaire system, understand the complexities of installation, and be cautious in considering long-term performance.”


“It’s important to remember the lamp and fixture are interacting with each other,” said Michael Royer of the Advanced Lighting Team at PNNL. “The electrical hardware and what lamp is best for that application is essential for success. Plug-and-play TLEDs seem to be a cost effective choice, but what’s the life of your ballast? Is there a compatibility issue [e.g., rapid start]? Would a retrofit of the fixture be the way to go?”


Royer said “caution” is the operative word when working with TLED retrofits. 


“Check out what’s going in the existing installation prior to the retrofit,” he said. “Maybe the space has mixed ballasts. That’s a complication.”


Jay Sudhakaran, senior manager, product marketing—LED lamps for Philips Lighting North America, Somerset, N.J., helped break down the four installation options ECs face with TLEDs.


“In UL Type A retrofits, a TLED lamp can simply be popped into the existing fluorescent fixture,” Sudhakaran said. “You avoid rewiring the fixture. However, success is dependent on a few things. Does the socket match the prongs of the TLED? You may need to retrofit the socket. Tubular LED replacement lamps often require unshunted lampholders. What’s the age of the ballasts? You don’t want to retrofit twice over a short period of time.”


An integrated driver (UL Type B) is another approach, eliminating the ballast altogether.


“The [120-volt] driver is in the lamp itself,” he said. “For some customers, the main reason to pull out ballasts is to reduce maintenance costs down the road.”


A third approach uses an external driver (UL Type C). 


“A dedicated LED driver also allows you to remove the ballast and install an LED driver into the troffer,” Sudhakaran said. “This approach is optimal for low-wattage LED performance. You might reduce overall system wattage by 2 to 3 watts [W].”


Finally, an all-out retrofit would involve replacing existing fluorescent fixtures with dedicated LED troffers.


“For example, instead of running 65W with two fluorescent tubes and ballast, you’re down to a dedicated LED troffer running 20W with no ballast system loss,” Sudhakaran said. “You instantly have a system that is eminently long-life, measurable and predictable.”


Like other TLED manufacturers, Sudhakaran said customers should view TLEDs as a luminaire system, i.e., lamp and fixture.


“Look at system wattage,” he said. “That is what you are truly consuming and can vary based on ballast load and interoperability. How will you use the product? Is it to extend the life and reduce total cost? In that case, a new fixture or retrofit kit is best. A driver will allow you to help dim a TLED. Recognize that using a ballast offers slightly less efficiency. Without a ballast, you’ll need to turn to an unshunted socket. Dedicated LED luminaire fixtures are more often used in new construction or major retrofits.”


UL Classified maintains a fixture must be installed by a certified electrician. The TLED installer is responsible for adding a visible sticker (when mains wiring is altered) indicating the fixture has been modified and can no longer use a fluorescent lamp. For Type A, UL Classified may not need the sticker but a set of compatible/reference ballasts must be explicitly available with the product.


“We and other manufacturers are trying to figure out how we might physically make TLEDs somewhat distinguishable from fluorescents as an alternative to stickers,” Sudhakaran said.


Other considerations


Dave Moeller, market manager of lighting for Graybar, St. Louis, sees the role of TLEDs increasing in the coming years. 


“We are seeing sales of TLED rise pretty dramatically,” he said. “Customers are also replacing old fixtures or retrofitting existing ones.”


Moeller added that LED is a still developing technology, so it’s important to ask when an LED a retrofit makes sense. 


“Some high-performing fluorescent can reach 90,000 hours for long-life application,” he said. “T5 high bays can provide 30 percent more lighting than the TLED in such an application. [Has] the TLED product … earned an Energy Star rating or is cited through the DLC? What’s the lamp life? I want to know if the TLED is dimmable, the amount of lumens per watt (125 or higher) and degree of beam spread.”


Graybar created an upgrade option matrix helping customers decide when and which upgrades makes sense.


“Let your customers know the choices they have available and perhaps best fit based on their goals,” he said. “You don’t want them investing in retrofit kits that change the look of the fixture or change the appearance of the facility in an unsatisfactory way.”


Troffers are typically the best application for TLED. 


“If used in a suspended application, you won’t get the expected wash of light off the ceiling because TLEDs are not omnidirectional,” Moeller said. “Some companies say they’ve developed such TLEDs, but there can be a loss in efficiency. An added bonus of TLEDs is their disposal. The tubes don’t have mercury like fluorescent or HID.”


TLED lumen output is different, as well.


“Fluorescent tubes typically offer 2,500 to 2,900 lumens,” Sudhakaran said. “A TLED maybe 2,000. But don’t be thrown. TLED and its light directionality makes its foot-candles equal or greater to a fluorescent. Wide-beam dispersion TLEDs, however, can reduce foot-candles, while narrow-beam lamps can create dark and light pockets in your space. Make sure the LED luminance levels for your customers match the previous fluorescent space. Customers don’t want to see a perceptible difference between fluorescent lighting and the new TLEDs. That, in part, is why frosted tube TLEDs have become more relevant to the marketplace.”


Fixtures play a role, too. 


“In a deep parabolic, a 45-degree light beam spread might be a good match,” Moeller said.


The PNNL also offers guidance that pairs beam-width capacity to best-suited fixtures.


Color, light and trying before buying


Color temperature and light quality, among other characteristics, should be weighed between fluorescent and TLED lighting. That was another area of study in the recent CALiPER testing.


“We used 45 LED products in our analysis and discovered the light quality of TLEDs was pretty similar to fluorescents, maybe a slight improvement of 1 percent or so,” Royer said. “Being a digital lighting source, a TLED’s color temperature is controllable. You have better command with dimming and sensors, as well.”


All participants in this story found value in conducting a small pilot demo prior to a TLED installation to discover potential troubleshooting needs and confirm a satisfactory look of the lighting.


“The hurdle for incumbent technology is to better existing product,” Royer said. “Ask yourself, what can TLED do for me? Life, color, dim ability have tradeoffs between fluorescent and LED. If you are mining data from the LED Light Facts database, research how performance has changed for a TLED. Any deficiencies? What’s the typical light output? Our last CALiPER report is pretty positive showing TLEDs have been improving, but there are good fluorescent lamps out there, too. See what works for you.”


To learn more about the DOE and PNNL’s TLED research, visit http://energy.gov/sites/prod/files/2016/07/f33/snapshot2016_tleds.pdf and http://energy.gov/eere/ssl/led-linear-lamps-and-troffer-lighting.