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 panel lighting wholesale 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 panel lighting fixture (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.
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