A lighting system that provides optimized visibility and visual comfort helps promote a safe work environment and can increase productivity. When upgrading a system, don't just settle for existing light levels, which may be inadequate if the source has depreciated from its initial output.
If employees must use flashlights to accurately monitor gauges and check valves in the pumping station, it's safe to assume that current light levels are severely insufficient. Consult the latest recommendations of the Illuminating Engineering Society of North America (IES). The Recommended Practice for Industrial Lighting (RP-7) is also a great reference.
Consider the amount of light reaching both vertical and horizontal surfaces of the application (measured as “footcandles”) when selecting a lighting design. Well-lit, vertical surfaces are important for occupants to monitor gauges and work on equipment. Higher levels of light should be considered for tasks like equipment inspection and repair.
Getting the right quantity of light out of a luminaire does the facility no good if it doesn't evenly illuminate the workspace, or if it causes excessive glare that may compromise general visibility. A nonuniform space (think hot spots and dark spots) may be distracting depending on the task, and glare may cause discomfort and lower productivity. Selecting the most appropriate optical design and wattage can provide the correct balance between quantity and quality of light in the workspace.
Another consideration is color rendering, or the ability of the light source to represent an object's true color. If a plant employee is working in an area where pipes are color-labeled, it is important that those colors are rendered properly and visible in the space. This can be achieved with a high-CRI (color rendering index) light source.
All light sources — light-emitting diode (LED), fluorescent, metal halide, compact fluorescent, and incandescent — depreciate over time. Loss factors take into account all aspects of the environment, the luminaires' construction, and performance of the lamp source. To ensure the facility is providing adequate lighting over a specified period, these factors must be considered during the design phase.
Loss factors include luminaire dirt depreciation, lamp lumen depreciation, thermal factor, and ballast factor. Most luminaires in wastewater and water treatment plants will be enclosed and gasketed due to humidity and corrosion concerns. Dirt and dust are more likely to accumulate on this type of fixture than on an open fixture. As a result, less lumens or light will actually hit the work plane over time.
Lamp lumen depreciation is inherent to the design of any light source, and each depreciates at a different rate. For example, a standard linear fluorescent 32 W T8 lamp (bare) has initial lumens of approximately 2,900 and depreciates only 5% at 40% of its rated life (36,000 hours). However, the T8 lamp is also sensitive to ambient temperature fluctuations and won't achieve 100% lumen output if it is run hotter or cooler than its intended operating temperature.
LED technology is gaining a lot of traction in this industry; it's perceived to provide significantly longer life over the next best light-source technology. This is true with the right luminaire and under the right environmental conditions — the manner in which the internal LED temperature is managed has a direct and significant impact on both life and light output.
Luminaires that are unique to the wastewater and water treatment industry range from 50,000 to 70,000 hours of life before they depreciate by 30% (known as the L70 life). This doesn't mean, however, that they are maintenance-free. Other electrical components, such as the electrical driver, must also be rated for the same life for a truly maintenance-free luminaire.
Ask your lighting partner about the L70 life of specific luminaires at 25° C, 40° C and 55° C (or 77° F, 104° F, 131° F). What is the driver life at those specific ambient temperatures? Unlike traditional lamps, LEDs emit light in a highly directional beam, so the optical design of the luminaire is increasingly important to be visually comfortable for people moving about the space. Consider investing in a properly designed LED luminaire that can reduce your maintenance and energy costs.
With many lighting technologies on the market today, it's important to evaluate them per the application space, as each has its unique pros and cons. (See below)
Controls must also be considered in a lighting upgrade project. Today, many facilities run their luminaires 24/7 or use contactors to operate their lighting systems. With rapidly adopted legislation such as the EPA's Energy Policy Act, the California Energy Commission's Title 24, the International Energy Conservation Code (IECC), and policies of the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE), facilities can't ignore automated control.
Controls can be scaled to fit your budget. You can recude energy with simple ambient-light-detection devices such as photocells, or a more complex solution such as occupancy sensors that are integrated into the luminaire to relay panels and dimming systems. A Lighting Certified Professional can help design and specify a controls feature.