LEDs have become bright enough, rugged enough, and inexpensive enough to handle illumination chores inside industrial control cabinets.
Slavco Anastasov • Rittal Corp.
For many years, fluorescent technology was the only option for the internal lighting of industrial enclosures. Fluorescent light sources have many positives and are relatively inexpensive. But they have their share of negatives. Fluorescent lighting was developed nearly 100 years ago, and improvements in the technology have been slow. These low-pressure mercury-vapor gas-discharge lamps haven’t changed much over time. Early lights required a warm-up period before they reached their full lighting output. At the end-of-life, fluorescent bulbs have a reputation for flickering or developing pink or black spots at the end of the tube as they lose mercury. The tubes are fragile, and the mercury inside the bulbs requires special handling in disposal.
Today, LED (light emitting diode) lighting is the standard for industrial enclosures. The advantages are compelling enough to foster the adoption of LED lighting worldwide.
The function of lighting is, of course, to provide sufficient illumination for tasks at hand. Light brightness is measured in lumens, which is a rating of the amount of light emitted, as opposed to wattage, which defines the amount of energy used while emitting the light. LED lights are so energy-efficient that we can no longer rely upon wattage levels to indicate a light’s brightness. LED lights produce same brightness as incandescent or fluorescent sources using much less energy.
Illumination levels available from industrial enclosure lighting ranges from 400 to 1,200 lumens. The higher the lumens, the more brightness throughout an enclosure. The cover enclosing the cabinet light can also help disperse the light rays. Light covers can range in style from simple clear plastic to Fresnel covers that employ a prism effect to spread the light over a larger task surface.
LED lights come in a variety of color temperatures. Color temperature is expressed in kelvins, using the symbol K, a unit of measure for absolute temperature. Color temperatures over 5000 K are called cool colors (bluish white), while lower color temperatures (2700–3000 K) are called warm colors (yellowish white through red). The term warm in this context refers to the radiated heat flux of traditional incandescent lighting rather than to how hot the bulb gets.
For industrial applications, the color temperature can help differentiate among objects in an enclosure. If a space includes a variety of colored objects, a natural white bulb (4000-4500 K) gives maximum differentiation. If the space includes more greens and blues, a cooler light color spectrum of day white to cool white (6000-7000 K) may offer a visual advantage.
Within an enclosure, the ability to direct light toward a task improves maintenance efficiency. Adjustable light distribution focuses illumination as in, for example, rotating a Fresnel cover to bring up a different lighting pattern. Most manufacturers have adopted this feature in LED lighting to beam light on objects of interest.
Just as room lights in commercial buildings increasingly work from motion sensors, a motion sensor in an enclosure is a worthwhile convenience for maintenance tasks. This hands-free option eliminates the need to reach into the enclosure to activate a switch, an additional safety factor. Workers can immediately tackle the task at hand without needing a free hand to fumble for the light.
An integrated electrical outlet in the LED lighting fixture provides a convenient power source for maintenance. This option simplifies and speeds maintenance with an at-hand outlet for equipment. The internal outlet also eliminates the need to string power extension cords across the factory floor, presenting a tripping hazard for workers. Outlets combine convenience and safety for more efficiency.
It is important to mount the light in such a way that gives maximum visibility. The ability to mount the light fixture horizontally or vertically assures the right illumination. A tool-less clip mounting option provides a fast and easy way of mounting the lights at the correct position for any application. Screw fastening or options using a magnet are also commonly used.
The interior of enclosures can be quite crowded with limited space available. Flexible cable connections permit the LED light to sit precisely where space allows. A 90° rotating connection can let the fixture fit into position without any need to twist cables or bend wires to accommodate the LED light housing.
Whether re-positioning existing fixtures or installing fixtures into a new enclosure, the amount of time needed to assemble and install the equipment factors into the overall maintenance cost. Studies have shown that fixtures which can be installed in two minutes represent an 80% savings in maintenance time over more complicated assemblies. This seemingly small savings multiplies over the number of enclosures to be serviced.
LED lighting systems often employ a daisy chain scheme where one light fixture plugs into another on the route to the source of power. This sort of through-wiring minimizes the amount of wire devoted to lighting the cabinet. Different manufacturers recommend a maximum number of links for daisy chains ranging from 8 to 16 lights. With regard to powering lights, all makers of LED lights provide the option of an ac or dc power system. Voltage specifications vary from 20 to 24 V for dc systems, 100 to 240 V for ac.
All lighting systems are designed to fit in standard industrial enclosures ranging in length from 10 to 17 in. And UL certification on LED lights is important. The enclosure LED lights can be UL listed under a UL IFAM category code for LED surface-mounted luminaires, or classified as Recognized components under category code NITW2. Here NITW is the UL product category for industrial control panels. The suffix “2” on the category code NITW indicates a recognized part.
A review of LED lighting systems shows their benefits for enclosure lighting. Manufacturers continue to focus on improving lighting efficiency, energy efficiency and lighting system performance. Long-term, LEDs can save over 30% in energy costs and reduce maintenance man hours in installation, repair and replacement compared to fluorescent equivalents. And as recycling restrictions become more stringent, it will become more expensive to dispose of fluorescent lights because of the small amount of mercury each contains.
LED lighting will emerge as the industry standard for lighting industrial enclosures worldwide. With rising concerns about energy efficiency and recycling restrictions, LED lighting will become the long-term, economical choice.