Outfitting a warehouse with proper lighting is critical so workers can perform their tasks accurately, productively and safely. However, a range of lighting requirements throughout the facility adds a challenge to selecting the light that's right. Key factors to take into account include the types of tasks performed in various areas, the required amount and color of light to perform those tasks, and the configuration of the warehouse itself.

Fluorescent and high-intensity discharge lamps are the most common lights used today. Depending on the specific lighting technology, they deliver a range of efficiency and cost profiles.

Fluorescent lamps, which are typically shaped as straight, tubular bulbs, are well suited to warehouses requiring a substantial amount of white light for working with small materials.

To produce light, this type of lamp discharges a low-pressure mercury arc generating ultraviolet energy that activates the phosphor coating on the bulb's inner surface. Fluorescent lights utilize a power supply known as a ballast to stabilize the energy, which can be inconsistent, and keep the lamp operating with consistent light levels.

Lasting approximately 10,000 hours and producing 45 to 90 lumens per watt, fluorescent systems are recognized as offering a good lifespan and efficacy. Due to the bulb's long shape, light dispersion is difficult to control. Fluorescent lamps are therefore most effective mounted at heights of 15 feet or less, especially in warehouses with high ceilings that require 100 lumens per watt or more for adequate light.

Fluorescent lamps are often characterized as producing a desirable white light rather than the yellow or green tints created by some high-intensity discharge lamps. For applications where color identification is highly important, a lighting system with a high color rendering index (CRI) is typically required. Referring to the ability of a light source to represent an object's true colors, CRI is measured on a scale of 1 to 100, with 100 representing the level at which colors appear most natural. Fluorescent lights, which are ranked significantly above high-intensity discharge systems, typically have an index of 80.

Among the different sources of high-intensity discharge lamps are mercury vapor (MV), metal halide (MH), low-pressure sodium (LPS) and high-pressure sodium (HPS). Similar to fluorescent lamps, high-intensity discharge sources (HID) pass an electric current through a vapor containing various elements. This discharge occurs at high pressures and temperatures to produce light from the electric arc. While these light sources are more expensive to install than fluorescent lights, one HID fixture can achieve the same amount of light produced by numerous fluorescent systems.

Mercury vapor lamps, the first high-intensity discharge lamp created, operate at 30 to 60 lumens per watt for up to 24,000 hours. However, the light output diminishes greatly over time, limiting the lamp's effectiveness in warehouses. The lamp also requires four to seven minutes to warm up and reach its maximum light output. While mercury vapor lights had poor color performance when first developed, they have since been improved with phosphor-coated bulb walls.

Characterized by its radiation from a variety of metallic elements, metal halide lamps deliver 60 to 90 lumens per watt. This lamp can be used at heights above 15 feet and still supply adequate light at floor level.

Metal halide lights operate for 7,500 to 20,000 hours, depending on the bulb's wattage. Like high-pressure sodium lamps, they allow precise control of light dispersion because light emanates from the small arc tube rather than from the entire outer bulb of the lamp. Metal halide lamps have a CRI of 65. As a result, the white light produced makes a warehouse appear brighter than a facility with high-pressure sodium lamps.

In contrast to fluorescent lights, which provide light as soon as they are turned on, metal halide lamps require time to warm up and cool down. A drop in voltage or a power failure also requires 10 to 15 minutes for the lamp to cool down and five to seven minutes for it to heat back up.

Low-pressure sodium lamps offer 100 to 180 lumens per watt, the highest efficacy of all manufactured lamps. All of the light output, however, is concentrated in the yellow portion of the spectrum, which creates a low color rendition. The lamp's large arc tube also makes it difficult to control where the light falls. Low-pressure sodium lamps last approximately 18,000 hours.

High-pressure sodium lamps, recognized as having a high efficiency and the longest life of all high-intensity discharge sources, achieve as much as 80 to 140 lumens per watt.

While this lamp furnishes a lot of light, its CRI is only 20, giving the light a yellowish tint. In warehouses where operators read labels with colors or perform assembly work, a high-pressure sodium lamp generally is not preferable. However, for applications such as storage and shipping where color identification is not essential, this type of lighting system can be the most energy efficient and cost effective solution. These lamps use a ballast, produce heat during operation and require time to warm up and cool down.

Whether the source of light is fluorescent or high-intensity discharge, maintaining uniform lighting throughout the warehouse while minimizing glare is essential. To achieve lighting uniformity from the ceiling to the floor, it is common to install lighting fixtures with reflectors that direct light up to the ceiling. This light, known as "uplight," illuminates the ceiling and diminishes the "cavern effect" created by a dark ceiling area. The benefits of a well-illuminated ceiling are visual clarity and a feeling of increased spaciousness.

Options of reflectors include glass, acrylic and aluminum. Glass and acrylic fixtures provide approximately 15 to 20 percent uplight, making them particularly suitable for warehouses with a white or light-colored ceiling. Acrylic reflectors are particularly susceptible to heat and ultraviolet rays so when they are used with bulbs that emit a lot of heat, such as high-intensity discharge sources, the reflectors eventually turn brown. Aluminum reflectors, which supply little uplight, are acceptable for buildings that do not require a lot of light near the ceiling.

Here are some of the latest developments in warehouse lights that have recently crossed our editors' desks.

Available in 250- and 400-wattages, the MasterColor HPS-retro white lamp allows users to easily change a high-pressure sodium (HPS) lamp into a metal halide lamp by simply switching the bulb. Using the existing HPS ballast but operating at an improved color rendering index of 90 instead of 20, the metal-halide lamp uses ceramic arc tube technology to offer color stability and 85 percent lumen maintenance. The lamp also eliminates the need for regularly scheduled shut-offs.
Philips Lighting Co.
732-563-3039
www.lighting.philips.com
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Ideal for facilities with high ceilings, the Prismalume is a prismatic glass high intensity discharge lamp that supplies high levels of horizontal and illumination for a bright environment. The lamp delivers adequate uplight and controls the downlight in order to increase visibility and eliminate the "cavern effect" of uneven floor-to-ceiling lighting. Features include a non-deteriorating borosilicate glass reflector available in five sizes, a high efficiency ballast, a die-cast copper-free aluminum housing, and corrosion-resistant paint.
Holophane
740-345-9631
www.holophane.com
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Two high-intensity discharge lamps, the DKL-40VA-MH-A (metal halide) and the DKL-40VA-HPS-A (high-pressure sodium), offer enough light for workers to accurately read labels on packages in the rear of a 50-foot trailer. The metal halide dock light is equipped with a 100-watt bulb, providing a light output of 7,800 lumens. The high-pressure sodium lamp has a 50-watt bulb for up to 4,000 lumens. Both lamps have adjustable arms and feature 300-degree horizontal movement and 210-degree vertical movement.
Fostoria Industries Inc.
800-495-4525
www.fostoriaindustries.com
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Added to the line of PulseArc metal halide lamps are the high output and extra high output versions fitted with 320- and 350-watts respectively. These lamps operate on energy-saving ballasts for faster warm-up time. When used for extensive periods, the lamp life is 50 percent longer than standard metal halide lamps.
GE Lighting
800-GE-LAMPS
www.gelighting.com
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Two lights, the T5 Pentron and Pentron high-output linear fluorescent lamps, feature a slim profile of 5/8 inch diameter and as much as 95 percent lumen maintenance over the lamp life. The thin lamp design provides a highly concentrated light source while fitting into small spaces. Available in three color temperatures, the lamps feature a high color rendering index of 82 and operate at about 104 lumens per watt for up to 20,000 hours. The Pentron T5 can achieve 3650 lumens using a 35-watt bulb while the Pentron HO T5 delivers as much as 7500 lumens with an 80-watt bulb.
Osram Sylvania
978-777-1900
www.sylvania.com
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The Baylighter fluorescent lighting fixture available in a variety of wattages is ideal for high-bay ceiling areas. When specified with a one-, two-, and three-lamp ballast on three circuits, the versatile lighting system provides six levels of illumination, eliminating the need for expensive dimming ballasts and controls. The light features a 95 percent reflective aluminum reflector and is available for pendant, surface and recessed mountings. Optical options include prismatic acrylic lenses, high-impact lenses, and parabolic louvers.
Los Angeles Lighting Manufacturing Co.
626-454-8300
www.lalighting.com
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