LAURA PETERS evaluates the photometric, electrical, and financial hurdles to retrofitting linear fluorescent lamps with LED-based tubes, including both plug-and-play products and tubes that require rewiring.
In recent months, several manufacturers have introduced so-called plug-and-play LED linear lamps — fluorescent replacements that require no rewiring and simply snap into place (Fig. 1). These solutions are more expensive but easier to install than LED linear tubes that require removal of the ballast and direct connection to line voltage — a task best performed by a qualified electrician. However, both approaches have their pros and cons. And both approaches are significantly less expensive than replacing the whole fixture.
We will review the performance and financial considerations associated with ballast-bypass and plug-and-play LED linear lamp installations for offices, schools, retail outlets, and hospitals. We will also discuss the electrical safety concerns that have been raised regarding LED linear lamps. Most importantly, the article will discuss the features to look for when considering LED linear lamp purchases.
Fluorescents versus LEDs: Then and now
Philips estimates the current installed base of fluorescent tubes at 12 billion sockets globally. In 2010, the US Department of Energy (DOE) estimated there were nearly 1 billion fluorescent luminaires installed in the United States, 60% of which were T8s (tubular, 8/8- or 1-in. diameter). Fluorescent T8 luminaires are mainstays in schools, hospitals, grocery stores, warehouses, and office spaces in the United States, but also in many other parts of the world.
In grocers and big-box stores, linear LED replacements have been making significant inroads in refrigerated display-case lighting. This is an ideal application for linear LED lamps because lifetime of the LEDs is extended in cold environments and the lamps don’t emit heat like fluorescent tubes, providing further savings on cooling costs. Because speed of installation is critical to grocery store owners, case lighting is a key target application for plug-and-play LED linear lamps.
Despite the success of LED linear lamps in this one application, they have struggled to compete with fluorescents across the board due to fluorescent tubes' relatively high efficacy (90 lm/W), long life (30,000 hr), and low cost. Priced at $3 per tube relative to $30 or more for an LED linear lamp, the LED replacement must match the fluorescent's light quality while significantly improving the energy efficiency to offer a reasonable return-on-investment (ROI) period. Nonetheless, as the performance of solid-state lighting (SSL) has steadily improved, LED linear lamps have become more competitive in terms of light quality and efficiency.
However, as was pointed out in a recent US DOE series of Caliper reports (Reports 21, 21.1, 21.2, and 21.3), not all LED linear lamps are created equal and lamps must be evaluated on a case-by-case basis. Report 21 began by testing the photometric performance of 31 linear LED lamps (sold in late 2012 and early 2013) and benchmarking them against 32W fluorescent tubes. Upon testing, only 8 LED lamps achieved the DesignLights Consortium (DLC) requirements for bare lamp efficacy (≥100 lm/W) and output (≥1600 lm), and only one lamp achieved output comparable to a 32W fluorescent (3126 lm) as shown in Fig. 2. Reports 21.1 and 21.2 evaluated 31 linear LED lamps in K12-lensed troffers and then three lamps in five different troffer types, respectively. When LED linear lamps are in a luminaire, multiple factors determine the luminaire output and luminous distribution including the lumen output and luminous distribution of the lamp, lamp cover (clear or diffuse), and troffer type.
In the prismatic K12 lensed troffer, 10 of the lamps provided lumen output comparable to the fluorescent and one lamp provided higher lumen output, with 20 lamps measuring lower output. Higher efficacy was maintained with K12 lensed and parabolic troffers, while recessed indirect troffers tend to reduce the efficiency of LED lamps to below that of fluorescents unless the LED lamp uses a high beam angle (Fig. 3). The Caliper study also indicated that observers preferred LED lamps with diffuse covers over clear lamps, and the diffuse lamps also lead to a luminous intensity distribution closer to that of a fluorescent tube's distribution, which is also preferred.
What does plug-and-play mean?
Still, the market potential has lighting manufacturers rushing new products to market including the so-called plug-and-play products. Plug and play implies that with power switched off, a fluorescent tube is snapped out of place, the LED lamp with identical bi-pin socket (G13) is snapped into place, power is restored, and the LED lamp instantly illuminates. The manufacturers of 4-ft T8 LED linear lamps have worked hard to match features of the 32W 4-ft T8 fluorescent including output of 1600–2000 lm, greater than 90 lm/W efficacy, ≥80 CRI at warm (3000K, 3500K) and natural white (4000K) CCTs, and a wide enough beam angle to provide uniform light distribution.
"When people test our lamps either alone or in the troffers, we don't want them to perceive worse light or insufficient light; we want it to match their previous experience or be slightly better," said Jeff Hungarter, product portfolio manager at Cree.
Cree recently introduced its LED T8 Series of lamps that deliver 2100 lm output at 21W, 90 CRI, and a 220˚ beam angle. The lamps are slightly oval in shape (Fig. 4), which provides a portion of the light as uplight (similar to a fluorescent), and are offered in 3500K and 4000K models. Regarding the motivation behind developing a plug-and-play linear LED lamp, Hungarter said, "Many retrofit customers were seeking a simple solution that would not disrupt their workplace and provided an ROI within three years — while improving light and color quality." Because of its performance and five-year warranty, the Cree LED T8 Series meets DLC requirements, enabling eligibility for many regional utility rebates.
In addition to Cree, other manufacturers of plug-and-play LED lamps include a small but growing number of companies including Alite, Kumho Electric USA, Luxul Technology, Philips Lighting, and Raise Energy Solutions.
The Alite Co. Ltd. offers an LED-Tube3 plug-and-play lamp that uses 20W of power to produce 1850 lm at 3000K or 2000 lm at 4000K, 5000K, and 6500K. With a CRI greater than 80 and beam angle of 180˚, the lamp is offered with clear, frosted, or striped tube finishes.
Kumho Electric USA manufactures Earthcare LED T8 plug-and-play lamps that are compatible with instant-start electronic ballasts. The lamps produce 2500 lm using 22W of input power, produce a 110˚ beam angle, and are available in 3500K, 4100K, and 5000K models.
James Pan, CEO of Luxul Technology, said one of the key challenges in developing plug-and-play LED linear lamps is simultaneously achieving excellent lighting quality with an integrated, universally compatible driver. "To achieve compatibility with most of the existing electronic ballasts and magnetic ballasts, we needed to develop a driver that interprets the ballast protocol and communicates the appropriate signal to the lamp." Luxul claims its lamps have proved compatible with more than 2000 commercially available ballasts. The Luxul Eazylux T8 lamps provide 1850–1950 lm using 17W of power (efficacy of 109–115 lm/W) at a CRI of 85 and color temperatures of 3000K to 6500K.
Pan added that while magnetic and hybrid ballasts are often considered yesterday's technology and something that is being phased out, for very cold environments, magnetic ballasts can offer significantly longer life than electronic ballasts. "For instance, in harsh, cold conditions, electronic ballasts may require replacement after only a year, whereas magnetic ballasts or programmable ballasts, which have a magnetic core, can last as long as 10 years. Beyond that, depending on how the loading is configured, efficacies on the order of 90 lm/W can be reached with a magnetic or programmable ballast and LED lamp," said Pan.
Philips InstantFit LED T8 is plug-and-play compatible with instant-start electronic ballasts, which the company contends represents 80% of the installed electronic ballast market. The InstantFit lamp uses 14.5W to produce 1500–1650 lm output at 3000K, 3500K, 4000K, and 5000K with a CRI of 83 and beam angle of 160˚.
Raise Energy Solutions produces an 18W plug-and-play LED linear lamp that produces 1700–1900 lm at 3000K to 6500K and CRI of 80. The beam angle is 150˚ and the lamps are offered with clear, frosted, or striped finishes.
"Considerations for purchasing LED linear lamps" presents a list of guidelines to use when purchasing LED linear lamps — whether one is considering plug-and-play, ballast-bypass, or lamp and driver retrofit kit solutions. Of course, any evaluation must involve the initial determination of whether the lamp model in question meets the performance requirements for the given application. Beyond this baseline qualification, one should assess the company's history in lighting and the manufacture of LED linear lamps in particular, look for relevant certification markings, and ask for supporting documentation such as the LM-79 report and warranty details. Importantly, testing of the lamps on-site is the best measure of whether or not they will perform suitably in one's application.
One example of the successful implemen- tation of plug-and-play lamps was realized at an Allstate Insurance office space in Wellington, FL. This facility achieved a noticeable improvement in light quality and realized a 44% energy savings when it upgraded from 4-ft fluorescent tubes to Philips LED T8 InstantFit lamps. LED Source provided the upgrade of 41 tubes utilized in a mix of two-, three-, and four-lamp luminaires.
Tom Neumann, the Allstate representative who was leasing the office space, said he preferred to upgrade the lamps because it was less expensive than other LED upgrades and he now has the option to take the LED lamps with him if he relocates. Energy use from lighting dropped from 3,256 kWh to 1,980 kWh per year, while annual maintenance cost was reduced by $135. Before and after photos of the office (Fig. 5) demonstrate the improvement in lighting quality and consistency with the LED lighting. "My staff is happy because they now have bright lights for better working conditions," said Neumann.
A final consideration with plug-and-play lighting installation techniques involves evaluation of the installed ballast. New high-efficiency instant-start ballasts are priced at $17 and consume less power than older instant-start ballasts, for instance, so a ballast upgrade may be considered and recommended if it is approaching 30,000 hours of use.
The ballast-bypass approach
As noted previously, a qualified electrician is recommended for retrofitting fluorescent tubes to LED linear lamps in a case where rewiring is involved — for example, with ballast-bypass lamps. In addition, because there is no industry-standard wiring configuration, companies have developed a variety of approaches, and the installer must follow instructions.
Fluorescent lamps that operate on instant-start electronic ballasts use shunted lamp holders (sockets with electrically connected terminals) while rapid-start electronic ballasts use non-shunted lamp holders. Magnetic ballasts, commonly used on outdoor signs, also typically connect to non-shunted sockets. In terms of LED lamps, either shunted or non-shunted lamp holders will be specified by the lamp manufacturer and included in the retrofit kit.
Among the 31 linear lamps tested in the aforementioned DOE Caliper report, seven different wiring configurations were used. Among the options, single- or double-ended wiring to the lamp, and shunted or non-shunted sockets are possible scenarios a retrofit installer might face. In two lamps, additional wiring was required between the two end connectors. This type of variation among commercial products introduces confusion among purchasers and can introduce safety issues since false assumptions can be made by installers.
There are pros and cons in selecting linear lamps with internal or external drivers. The internal driver occupies part of the tube and therefore LEDs may not run the full length of the tube, which may/may not significantly affect light distribution in an application. Also, with all the driver electronics confined to the small area inside the linear tube, that area of the tube must be kept cool and it is more of a challenge to integrate smart functions such as 0–10V or DALI-controlled dimming. Such advanced electronic features are readily incorporated into external drivers. Lamps with external drivers also feature a longer warranty, typically 7 years versus 5 years.
There are many manufacturers of linear LED lamps and linear LED retrofit kits. To give readers a sense of how many LED linear options are available, the list of lamps on the DesignLights Consortium Qualified Product List (QPL) in the 4-ft linear replacement lamp category includes 4,115 lamps. The total number of QPL products is 48,835, so T8 LED lamp replacements account for more than 8% of all listed products.
Safety and certification
Like other lamps, all linear LED lamps (including plug-and-play) must meet the Standard C22.2 No. 1993-2012 – Self-ballasted lamps and lamp adapters. Retrofit lamps (ballast-bypass and LED lamps retrofit kits that include a driver) must additionally meet the standard ANSI/UL 1598C – 2014, Standard for light emitting diode (LED) retrofit luminaire conversion kits.
Both the UL (Underwriters Laboratories) and ETL (Electrical Testing Labs) marks demonstrate compliance with the minimum requirements of widely-accepted LED lamp safety standards as determined through the independent testing by UL or a third-party Nationally Recognized Testing Laboratory (NRTL). An NRTL is an independent laboratory recognized by the Occupational Safety and Health Administration (OSHA) to test and certify lamps to the specifications of applicable safety standards. As part of that testing regimen, the lamp manufacturer has agreed to periodic follow-up inspections to verify continued compliance.
Carl Bloomfield, global director of business services for the lighting industry at Intertek, explained that regardless of implementation type (plug-and-play LED linear lamps, ballast-bypass linear lamps, or linear lamps with a LED driver), the products are all tested in an existing fixture to the same standards for risk of fire, electric shock, or mechanical hazard. He explained that mechanical hazard includes issues such as whether certified sockets can hold the LED lamps, which tend to be heavier than fluorescent tubes, or whether there is sufficient clearance between the ballast/lamps or driver/lamps for installation.
Shock and fire hazard is evaluated by simulating and testing worst-case scenarios for current surges and temperature increases. One example of a shock hazard with early LED linear lamps resulted when an LED lamp was inserted into a socket, power turned on, and the exposed end provided a shock hazard. Fire hazards can result from damage to the lamp or wiring that occurs during installation. Bloomfield added, "The standards are continually being updated as the LED lamp offerings change. We test for new risks as they become evident."
Return on investment
In closing, let's discuss ROI. LED linear lamps that produce equivalent light levels and light quality to 32W fluorescents at around 20W will save around 35% in energy costs and some manufacturers are claiming 50% savings.
The DOE performed a detailed lifecycle cost analysis in Report 21.3, comparing a 2×4-ft luminaire with two fluorescent tubes (51W) versus two LED linear lamps (38W), with fluorescent system cost of $30 versus variable LED system cost of $40, $80, or $120 (including driver). While we'll leave the details to the readers to explore, the simulation determined a 2-year or less simple payback if the lamps operate 4,000 hr/year (12 hr/day) and: electricity cost is $0.12/kWh or greater and LED system cost is $40; electricity cost is $0.24/kWh and LED system cost is $80 and it is installed in 15 minutes (not 30 minutes). If the lamps operate only 2,000 hr/yr (6 hr/day), 1-year simple payback is possible at all electricity rates ($0.06–$0.24/kWh) when the system price is $40 and it can be installed in 15 minutes.
Just as the performance evaluation for LED linear lamps should be done on a case-by-case basis, a detailed ROI analysis should also be performed.
The two performance metrics that have long stopped LED linear lamps from competing with fluorescent tubes — comparable light quality and efficacy — are being overcome with today’s highest-performing lamps. As SSL technology continues to advance, LED linear lamps and the expanding lines of plug-and-play lamps will only become more enticing for conversion.
Plug-and-play LED linear lamps provide a convenient and simple option for businesses seeking rapid installation of LED linear lamps. Ballast-bypass approaches are less expensive, but the overall cost is offset by labor installation cost and perhaps disruption to the business environment (the "time is money" effect). LED lamps and drivers (kits) may be preferred when advanced electronic functions are required by the application.
LAURA PETERS is a contributing editor with LEDs Magazine and Illumination in Focus.
Considerations for purchasing LED linear lamps
• Has the lamp attained relevant certifications [i.e., UL/cUL, RoHS, CE, CCC (China), etc.]?
• Can the company provide an IES LM-79 report for the lamp?
• If the lamp will be used outside or in an industrial environment, check for IP6X rating and make sure the lamp and ballast are designed to withstand the environment.
• How long has the company been in business? How long have they been manufacturing LED linear lamps?
• Will the company allow me to test the lamps in my application? If dimming is required, test the lamps for flicker upon dimming.
• Is the model I am evaluating listed on the DesignLights Consortium Qualified Products List? If so, what rebate(s) am I eligible to receive?
• What is the product warranty and terms of the warranty?