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Saving Energy

April 1, 2003
Regulatory pressures and the global move toward a reduction in unnecessary energy use continue to drive the energy conservation market.In the past few

Regulatory pressures and the global move toward a reduction in unnecessary energy use continue to drive the energy conservation market.

In the past few years, electric utility companies have used demand side management programs to reduce electric energy demand. As part of the overall strategy, they applied incentives in the form of energy rebates. In many cases, utilities worked in conjunction with contractors to recommend products and value-added services to commercial and industrial customers.

At this time, retrofit projects continue to happen despite the reduction in utility incentives and energy rebates. It is not necessary for energy users to wait and see if utility deregulation will lower rates enough before doing a lighting retrofit. You can finance many retrofits in such a way that the energy savings more than pay for the cost of the new lighting system. In some cases, the building owner can even enjoy a positive cash flow.

Electrical distributors can take heart from this news. You can still make money by proposing viable retrofits. Specifically, it is worthwhile reviewing fluorescent lighting technology because of recent improvements in both lamps and ballast components.

The standard T12 40W lamp, used in the industry since the inception of the fluorescent lamp, has given ground to the 32W T8, high color rendering index (CRI) lamp. And the T8 lamp gains its highest performance when served by an electronic ballast, which offers substantial improvements in performance and reliability, compared with the 60-Hz operation of a core and coil magnetic ballast.

Another important characteristic of an electronic ballast is the ability to serve the lamps at various light outputs. Ballast factor (BF) achieves this. BF is the percentage of lumens from a lamp operated by the actual ballast compared with the lumens from the same lamp type operating with a test bench or laboratory standard ballast. Thus, an electronic ballast can have a low (around 70%), normal (around 85% to 95%), or high (above 100%) ballast factor. Here are the details:

*Partial-output electronic ballasts. Low or partial output electronic ballasts are useful when you desire reduced illumination, such as a computer-intensive office where delamping (which is simply the removal of one or more lamps) of existing fixtures achieves the 20 to 30 footcandles recommended for the ambient component of a task/ambient lighting system. Thus, while delamping alone can result in uneven luminaire brightness, a reduced-output electronic ballast can provide uniform reduced luminaire brightness across the entire luminaire aperture and also deliver the appropriate amount of illumination on task surfaces.

*Full output electronic ballasts. In nearly every fluorescent lighting system, a full-output electronic ballast can replace a core and coil magnetic ballast. Where feasible, the use of three- and four-lamp ballasts instead of two-lamp ballasts can save money (material, labor, and energy costs). In applications with two-lamp luminaires, consider tandem-wiring a pair of two-lamp luminaires to share a single four-lamp ballast. In this situation, your customers should check with the manufacturer on the maximum lead length between the lamp sockets and ballast.

Keep in mind many T8 electronic ballasts have unique wiring diagrams. Become familiar with the wiring diagram for a brand you are selling for the first time; thus you can help customers prevent problems later.

In 1994, a performance standard for electronic ballasts, ANSI C82.11-1993, High Frequency Fluorescent Lamp Ballasts, was issued. This standard established, as a maximum value, a 32% total harmonic distortion (THD). Most of the electronic ballasts used today have a 20% THD, although some products are available with a THD in the range of 5%. While this low harmonic level has no effect on the power consumed, it may have a very positive effect within the power system since this reduces the total harmonics present.

Other ballast choices. Since not every project requires the use of electronic ballasts, your customers should also consider the application of hybrid magnetic ballasts. Also called a cathode disconnect ballast, this unit is a standard magnetic ballast that removes power to the cathode heater circuits (the lamp filaments) after the fluorescent lamps are lit. This results in an additional 2W savings per lamp during operation. This type of ballast, which is about $4 less expensive than an electronic ballast, is suitable for all two-lamp ballast applications with 4-ft T8, T10, or T12 rapid-start fluorescent lamps.

In a room where electromagnetic interference (EMI) from an electronic ballast is a potential problem, the hybrid magnetic ballast-with a slightly lower EMI-should be considered. Your customers should not use the hybrid ballast, which is available as either a full-output or partial-output model, in any dimming application or with 32W heater cutout type lamps.

Upgrading commercial lighting systems. When owners have to upgrade a commercial lighting system, they can follow either of two approaches:

*Remove old fixtures and replace them with fixtures that better serve the lighting application.

*Retrofit the old fixtures with new ballasts, lamps and perhaps lenses. Retrofitting an existing luminaire can involve delamping and the use of higher output lamps, a reflector, and the cleaning of the luminaire interior surface.

While the number of lamps removed directly determines light level reduction, another factor exists. In an enclosed luminaire, de-lamping will bring a 5% to 10% increase in efficacy (lumens per watt), because the lamps operate cooler within the enclosure, and there are fewer lamps to block the total lumen output of the fixture.

Delamping may not be suitable for series-wired, two-lamp luminaires where the removal of one lamp extinguishes the other. In such cases, your customers should consider installing a partial-output (low ballast factor) electronic ballast to operate both lamps at reduced wattage and reduced output.

New lens patterns improve appearance. New lens patterns accentuate uneven light levels when delamping fixtures in overlit spaces. They also "fill in" dark areas at task level by more widely distributing the light, while "hiding" the shadows in fixtures where lamps are removed. Other lenses cut VDT computer screen glare by narrowing beam spread in one plane while widening it in the other, filling in potential dark areas to the sides of the VDT.

Asymmetrical distribution flat lenses can help. These flat lenses have proven useful during lighting upgrades and for new fixtures equipped with special reflector designs. Specular reflectors, for example, can make lighting fixtures appear more glary (even when they do not change the spacing to mounting height), but adding such a widespread lens can reduce the fixture's apparent brightness while distributing light more evenly.

Two more accessory products are available for both existing and new fixtures. Designed to allow re-use of existing, poorly spaced fluorescent pendant fixtures, a specular reflector with widespread distribution along with a lamp socket relocation device raises the spacing to mounting height (S/MH) ratio of a fixture from the usual 1:2 up to 1:5.

The second product is a lens that looks like an upside-down pyramid stretched along one axis. The lens has up to 40% more surface area than a flat lens of the same width. The ends of the lens also angle to alter the light distribution. A basement hallway used for locker storage is an application suited for these two products. The existing two-lamp recessed one-by-four fixtures were up to 18 ft apart in a 10-ft ceiling, delivering a 6:1 ratio of illumination, when measured at floor level under and between fixtures.

A widespread specular reflector was added dropping the light level ratio to about 2:1, thus greatly reducing the horizontal fc variations. When the pyramid lens was added, the ratio of illumination was further reduced to a desirable 1:1.

Economical dimming of fluorescent lamps. Saving energy with dimmable ballasts requires careful coordination and proper equipment selection.

The 10-0VDC control system is rapidly becoming the industry standard for continuous dimming of T8 fluorescent lamps from 100% to 20% output, and these ballasts are available presently only in the two-lamp configuration. Because these latest dimming ballasts are quite cost-effective, their applications are expanding. At 20% of full light output (maximum dimming), the system efficacy drops from about 84 lumens per watt (LPW) to about 58 LPW. A 70% reduction in power consumption accompanies this 80% reduction in light output.

The external control device can be a manual wallbox control, photoelectric light sensor, occupancy sensor, or system controller. All of these control devices send a low-voltage signal to the ballast using two control input leads, one with violet color, the other with gray color to the conductor insulation.

When more than one device is controlling the ballast output (for example, a photosensor or an occupancy sensor), you can use an integrated load controller to determine the appropriate signal to send to the ballast.

A dimming ballast achieves maximum lamp life by controlling minimum lamp current, lamp starting, cathode voltage, and lamp current crest factor (LCCF), the ratio of peak lamp current to RMS lamp current.

Many buildings now use occupancy sensor and timers to turn lights off in areas not used much, such as meeting rooms, bathrooms, warehouses and other types of storage areas. Engineers and designers used to debate whether instant-start or rapid-start electronic ballasts were better to use with these control devices. Studies show that instant-start ballasts provide maximum energy savings, but rapid-start ballasts are the economical choice when lighting loads are turned on and off quite often.

Ambient lighting: Lighting provided throughout an area. Uniform general illumination.

Ballast: A device that modifies incoming voltage and current to provide the circuit conditions necessary to start and operate electric-discharge lamps.

Ballast factor: The ratio of light output obtained by a commercial ballast to that obtained by a reference ballast.

Fluorescent lamp: A low-pressure mercury, electric-discharge lamp that uses a fluorescing coating (phosphor) to convert ultraviolet light energy into visible light.

Lumen: The unit of luminous flux (the time rate of flow of light). Measures the quantity of light produced by a light source. Defined as the quantity of light that falls on a 1-ft area surface that is equidistant 1 ft from a source whose intensity is 1 candela.

Luminaire: A complete lighting fixture including one or more lamps and sockets and a means for connection to a power source. It may also include one or more ballasts and elements.