When you're simply replacing lights in a warehouse, the process is fairly straightforward: you look at a bulb, fixture, or ballast and find a part number; then head to a website like LightingSupply.com, which is loaded with commercial lighting products, and search for that part number. Voila! Parts should arrive quickly and you don't need to give it more thought than that.
But warehouse lighting isn't always that simple. Sometimes the part you're replacing no longer exists and you need to find an adequate replacement. Sometimes you're looking for retrofit options. And sometimes you're thinking about an entirely new approach to lighting your warehouse. In these cases, here are some things to consider about warehouse lighting:
Types of Bulbs
Traditional light bulb selection for a warehouse includes High Intensity Discharge (HID) bulbs and fluorescent bulbs. Among HID bulbs, the two primary options are high pressure sodium bulbs and metal halide bulbs. Higher pressure sodium bulbs are attractive because they have a high efficacy level -- this means they produce a lot of light on a little energy. The drawback is that the quality of their light is very low, with a Color Rendering Index (CRI) of just 20 out of a possible 100 and a yellow-peach light color. These can work in some situations such as safety or street lighting, but are generally not meant for task lighting. It isn't ideal in a warehouse where someone may need to read a label or where there's much traffic or activity.
Metal halide bulbs cost more to operate than high pressure sodium, but they have a 65 CRI and offer a much whiter light. That makes them better for any kind of detailed work and for safety in general. Pulse start metal halide bulbs are more efficient than the standard type so, despite their greater cost up front, they will save money over time by using less energy and with a longer typical lifespan. They also have a quicker "restrike" time for cooling down and then turning back on (after a power outage, for instance).
In the past, these HIDs were used on high ceilings, as fluorescent bulbs couldn't produce enough light for warehouse lighting from above approximately 15 feet. So HIDs were used as "high bay" lighting while more efficient fluorescent bulbs were used as "low bay" lighting at lower heights -- perhaps over work stations, for instance.
Today, though, fluorescent bulbs have become more efficient and can offer ample light for a warehouse, so many warehouses are now moving away from HID lighting when they have the money to invest in a total relamping, which saves them money in the long term.
T8 fluorescent bulbs (tubes), for instance, now produce more light at 32 watts (or less) than older, 40-watt T12 bulbs. With their improved lighting, you can now use multi-lamp fluorescent fixtures running at less than 300 watts (including ballast losses) to replace 400-watt metal halide bulbs (running at more than 400 watts with ballast losses). Though this is just a simple example, you can imagine the annual savings in a warehouse with scores of metal halide bulbs to replace!
Besides energy efficiency, an advantage of fluorescent bulbs comes from their high CRI ranging from 70 CRI to above 90, allowing for excellent vision when compared to HID options. Fluorescent bulbs also turn on quickly, without the restrike time of HID bulbs. A downside of fluorescent bulbs is that they are more sensitive to temperature and may not work well in extreme heat or cold.
Besides T8 fluorescent bulbs, we now also have T5 fluorescent bulbs, including those with a high output option (designated by "HO"). These HO bulbs offer even greater lumen output than T8 and T12 bulbs, allowing you to use even fewer fixtures in certain settings. As with any fluorescent tube, T5 bulbs use reflective fixtures to drive more of their light down toward the areas needing light.
There are some other things to consider when choosing warehouse lighting. We'll touch briefly on them here.
How Much Lighting?
For many years, experts have called for an average of 30 footcandles (FC) of light at the working level in warehouses, but more recently this standard has been challenged as arbitrary, pointing to the fact that lighting levels should be adjusted by the amount of traffic in an overall warehouse and in specific areas; by the kind of work being done; by the reflective nature of walls, ceilings, and floors; and even by the light absorbing qualities of items stored in the warehouse.
If there are work or task stations in a warehouse, they're likely to need more lighting than areas where products are simply being picked off shelves. And if products are picked from a paper system rather than with helpful technology, more lights may be needed for reading!
At the end of the day, the answer to "How much lighting?" is really, "Whatever lighting is enough to do the job safely and do it well." You can measure lighting in an area with a light meter.
Placement of Lighting Fixtures
To get enough light into a warehouse, managers will sometimes opt to add more lights (or brighter lights) rather than considering where the lights are placed. In some cases, though, lights are just badly positioned -- above shelving, for instance, which ends up casting shadows onto the floors. Running bright, efficient bulbs down warehouse aisles, between shelves, is one example of improving lighting by location.
Other things to consider when lighting a warehouse is how often different areas are being used and what kind of added lighting you get from sunlight through windows or skylights. Automated controls can turn on and off lights, or brighten and dim them, according to ambient light levels caused by the sun or by movement of people and equipment in areas of the warehouse. This is an excellent way to save money on energy usage, which can be a substantial cost in warehouses.
One final point to be aware of is the advent of LED lighting. LED bulbs are even more efficient than fluorescent bulbs. They are bright, they render color nicely, and they're not sensitive to temperature like fluorescent bulbs. They are also directional, so they don't need the same kind of reflective fixtures to send their light toward a working area. The primary reason we don't see more LED lights in warehouses as of this writing (2014) is that the bulbs still have enough of a price gap that most businesses prefer to stick with fluorescent bulbs. As LED bulbs continue to fall in price, they may well become the warehouse lighting of choice.
We hope this article helps you to understand the basics of warehouse lighting. At Lighting Supply, we not only carry a wide selection of warehouse lights, fixtures, and ballasts, but our customer service representatives are certified lighting experts and can help to answer your questions if you want a guiding hand.