The Low Bay Lighting Low Down Boston MA

With many styles of lighting fixtures available today, it may be a little tricky to determine what type of lighting systems should be installed. Adding to the complexity, about 20 percent to 30 percent of total energy consumed by businesses is just for lighting. Companies are looking at every angle to maximize the energy efficiency of their facilities. This includes looking at the luminaries style and type of lamp used in their low bay systems.

To truly understand what is happening in the industry, we need to have a clear understanding of low bay lighting systems and how trends will affect decisions you make on your projects.

What is a Low Bay Fixture?

There are three main distinguishing features of a low bay fixture. A fixture is classified as "low bay" when the bottom of the unit is 12 feet to 20 feet from the ground. Next, low bay can be identified by a prismatic lens located on the bottom of the fixture. The purpose of the lens is two-fold: it serves as a shield to reduce the brightness of the light and also spreads the light evenly to achieve a smooth, even distribution.

Lastly, low bay fixtures typically exhibit smoother candlepower curves with wider spacing criteria, a ratio indicating the maximum recommended spacing allowed to maintain uniform illumination. This ratio is interpreted as the maximum distance in mounting heights that you can space your fixtures apart. In this case, the fixture mounting height is actually defined as the distance between the bottom of your luminaire and the top of your work plane height (the height of the surface at which you will ultimately measure or require your designed light levels).

Typically, low bay lighting is an ideal choice for industrial, commercial, distribution or retail applications. It's always a good idea to consult an application engineer to create a quality layout for your lighting project. Application engineers utilize ceiling height and other project-specific variables such as type of mounting, ballast design and optical system to determine which fixture works best for a particular setting. Ideally, a low bay installation should mate fixture, lamp type and wattage with a desirable mounting height and consistent spacing to ensure maximum lighting uniformity and optical distribution.

Available lamp styles

There are two basic lamp styles used with low bay lighting: high-intensity discharge (HID) lamps and linear fluorescent lamps.

HID lamps emit light from a capsule of gas rather than a filament. These lamps tend to produce a brighter, whiter light that is closer in appearance to natural lighting. The main variable you need to consider with an HID fixture is the aperture size, generally ranging from 16 inches to 30 inches in diameter. Typically, a wider aperture diameter creates a wider distribution that allows for greater spacing criteria with less source brightness.

"HIDs work very well," said Brian Geiger of Geiger Electric in Peoria, Ariz. "The prismatic lens does a good job of spreading light and the fixtures are also quick and easy to install. We usually have one guy mounting it and one guy on the ground level. It's very simple."

The second type of lamp, linear fluorescent, is available in two main models—T5HO and T8—with a varying number of lamps per fixture. These lamps are smaller in diameter but four inches long. They are capable of providing comparable light levels with less brightness, due mostly to their longer linear shape and reduced output per lamp.

Fluorescent lamps retain as much as 95 percent of their initial lumen output at 40 percent of rated life whereas HID lamp lumens can be anywhere from 60 percent to 85 percent of initial at 40 percent of rated lamp life. Most importantly, fluorescent lamps can offer up to a 50 percent energy savings compared to HID and last two to three times longer.

HID vs. linear fluorescent

More facilities are upgrading to linear fluorescent lamps from HID as they provide comparable levels of light compared to other types of lamps and require half the amount of energy to operate.

"Fluorescent low bays are one of our most popular fixtures," Geiger said. "I've been monitoring chain stores such as Wal-Mart and they're all starting to use a lot more linear fluorescent lights. People love the energy savings and rebates. The fixtures are a little bit pricy at first, but they use half the energy and get twice the light output. They're amazing."

There are three main reasons why businesses are upgrading from HID to linear fluorescent lamps. The first is energy utility companies offering rebate incentives to upgrade lighting technologies. Often, the value of the rebate program offsets the labor cost of retrofitting current fixtures, resulting in payback in as little as 16 months. Additionally, the 2005 Energy Policy Act may allow for tax deductions on energy efficient lighting upgrades.

Second, HIDs don't work well with occupancy sensors since the lamps cannot be restarted immediately after cooling and typically require at least 15 minutes to warm up. There are certain ballast models that allow for dimming of lamps to 50 percent if a sensor identifies the room as unoccupied.

The drawback of this type of feature is its lack of energy efficiency as power is always flowing to the unit whether the light is dimmed or fully illuminated. Adding a motion sensor to fluorescent lighting will increase a company's annual energy savings even more through a 25 percent (or lower) power draw in the low setting compared to the requisite 50 percent power draw with HID systems.

Lastly, linear fluorescent lamps offer additional benefits over HID lamps such as improved visual performance and longer lamp life. Fluorescent lamps also seem more widely available than HID systems, especially since more and more facilities are upgrading.

Choosing lamp styles

The justification for upgrading to fluorescent lamps may seem like an obvious decision after learning how these lamps maximize energy and cost savings, enhance performance, and propose utility rebates. Be cautious that linear fluorescent is indeed the best option for your application. Consider the point that linear fluorescent lamps may be too bright for the area of application. Just like HID, fluorescent lighting can be overbearing when it's mounted too low but in most cases, can be adjusted to suit application needs.

Also keep in mind that if the facility has less than ideal lighting conditions, upgrading a low bay system to linear fluorescent lamps will not help to solve the issues. Therefore, a redesign probably should be considered, which may translate to construction or added cost.

Lastly, the environment also plays a contributing factor. Linear fluorescent systems are more sensitive to extremes in temperature. Too hot or too cold of an environment can detrimentally impact the lumen output of your linear fluorescent system.

On the other hand, the operation of HID systems is fairly stable regardless of their ambient temperature range, which generally covers -40° C to as high as 60° C.

Facilities may choose to upgrade their low bay lighting systems with energy efficient linear fluorescent lamps now or later. One thing is clear: the sooner businesses strive for best practices in energy conservation and cost reduction, the faster they'll start to see the savings. Upgrading low bay lighting is an easy first step.

David Magruder is a freelance writer specializing in the lighting industry. Mike Krueger has been with Ruud Lighting for 20 years and manages the Application Engineering Team.