The Energy Policy Act of 1992 (EPACT) continues to influence the lighting industry, as manufacturers respond with a slew of energy-efficient lamps, while also playing up the concern for environmentally friendly designs.
For example, there now is a T8 lamp to replace nearly every common length, shape, and contact pin configuration of existing - or outlawed - T12 lamps. And a wider array of electronic ballasts in both rapid start and instant start configuration is available for these linear T8 lamps, with more features such as continuous and step dimming and other control capabilities. Also emerging are "any voltage" models that sense - and then correspond to - the voltage of the circuit being connected.
At the same time, lamp manufacturers are increasingly promoting T8/fluorescent (electronic) ballast systems that optimize the characteristics of each component, so that the specifiers increasingly are using a "systems concept" in selecting products.
Most industry specialists recommend using fluorescent electronic ballasts with less than 20% total-harmonic-distortion (THD), and even down to about 10% THD. And they are being specified in increasing numbers. However, designers should carefully consider their selection. The reason is that the low total-harmonic-distortion circuitry provided by many - but not all - of these electronic ballasts, also has a high initial inrush current, which is the instantaneous current drawn by the ballast on the lighting branch circuit when it is first energized. (The early electronic and hybrid ballasts used an inductor, or choke coil, to offset the effect of the internal capacitor used to increase power factor, and this coil secondarily limited current inrush when the circuits were energized.)
Today's low THD ballasts don't have an inductor, using instead integrated circuits to correct the power factor and reduce THD, and a variety of conditions must be present simultaneously for high inrush current to be considered an issue. But when these conditions are present, it can cause tripping of a circuit breaker or damage to the contacts of load-switching equipment (relays and contactors) that usually are adequately sized to handle the typical lower inrush currents of the past.
For example, some of these electronic ballasts can have an inrush current as high as 475A on a fully loaded 16A max rated (for 3-hr continuous operation, per NEC rules) 20A circuit. Fortunately, these conditions are not always seen in a retrofit project because the total load on each lighting circuit is often substantially reduced. But for a new or replacement lighting system design, where each 20A branch circuit will most likely be loaded to 16A, the issue of initial inrush current should be considered.
Other than taking care to select electronic ballasts without the high inrush characteristic, there are two other strategies to consider: Specify lighting controls that use solid-state zero crossing relays, or insert negative temperature thermistors in series with the ballasts of the circuit.
Just when the T8 fluorescent lamp has become the overwhelming choice for general lighting in offices, lamp makers introduced a new concept fluorescent lighting system designed for buildings that are built using metric specifications. The new system consists of a T5 (or 5/8-in.-dia) lamp and an efficient electronic ballast. Representing the first major change in linear fluorescent lighting in more than a decade, the T5 lamp allows for a reduction in the depth of a troffer, providing a wide variety of options for indirect or display lighting applications. Available in 563-, 1163-, and 1463-mm sizes, each lamp in the family is shorter and narrower than comparable T8 lamps in the 2 ft to 5 ft range. With up to 105 lumens per watt, the new lamps are also 12% to 18% more efficient than standard T8 lamps and have 95% lumen maintenance.
The smaller size means less material such as glass, phosphor and fill gas is used to manufacture the T5; it can be packaged in a small, lightweight carton for transport; it also has less weight and volume for disposal or recycling, making the T5 a resource-efficient product over its life cycle.
While considering all of these selling features, note also that these metric-sized lamps, which are used in Europe, don't fit standard 4-ft-long fluorescent fixtures. Thus, the lamp must be integrated into a building's ceiling grid system using other than a 2-by-4 ft module, and another element to consider is added to the design process.
But using this new technology also means that a specifier must take time to learn about these lamp products and the ballasts that work with them. Basically, "there ain't no free lunch."