Lighting Controls: Energy-Efficiency Edge
Advances in lighting controls have given managers in institutional and commercial facilities enhanced ability to control energy costs and provide better lighting for facility occupants and visitors.
By taking a closer look at recent advances in lighting control technology, managers can develop and refine guidelines for planning upgrades to lighting controls and better understand the role of lighting controls in qualifying for tax deductions under the Energy Policy Act of 2005 (EPAct).
Inefficiency on Display
The need for lighting controls is on display around the clock. Interior building lights burn all night, and outdoor lights burn all day. It’s as though facilities are permanently on and incurring unnecessary energy costs.
The most effective way to reduce lighting costs is to turn off lights. But there are many reasons lights remain on. Facilities often find themselves with complex lighting control systems that are difficult to manage, and in many cases, are bypassed by system technicians.
Simpler controls can be more effective. For example, managers can specify special switches to replace standard line switches. When operated manually, these switches turn lighting systems on and off. Switches left on are physically released, turning off lights after normal work hours. This action is the result of the momentary operation of relays by a time clock or building automation system.
Other time-activated, after-hours sweep systems pulse off low-voltage lighting relays by using an electronic sequencer. These sweep systems meet the requirement of ASHRAE/IESNA 90.1 for buildings larger than 5,000 square feet.
Occupancy sensors also can help organizations meet the requirement. Sensors, however, are not appropriate in some spaces. In open-plan offices or classrooms, for example, there is a greater potential for false-off situations than in small offices, restrooms or conference rooms, where the effectiveness of occupancy sensors has been proven.
In some cases, technicians install sensors with little or no attention to proper adjustment — a step in building commissioning — or to monitoring for proper operation. A recent survey found that occupancy sensors with a time delay of 10 minutes or less have higher callback rates for adjustments that those set with delays of 15 minutes or longer. The difference suggests a need for self-calibrating occupancy sensors to reduce callbacks.
The shorter the time delay, the greater the amount of savings. But unless managers specify programmed-start lighting ballasts, time delays of less than 15 minutes usually will reduce lamp life. For many applications, delays of no less than 15 minutes are specified when instant-start ballasts are switched.
The sensitivity control determines the amount of movement that will cause the sensor to activate the lights. When this control is set too high, the possibility of false-ons increases. When it is set too low, the potential for false-offs increases.
But managers must be aware that changing the sensitivity control also changes the coverage pattern. Sensors arrive in facilities with a factory-set sensitivity setting. Installers should adjust them to meet the application requirements.
By doing so, sensors will respond properly to the main tasks in the space at the correct distance. Installers also must take into account potential sources of nuisance switching, such as air flow.
ASHRAE/IESNA 90.1 is the energy conservation standard used in most states. Some states have adopted the International Energy Conservation Code (IECC), which is based on 90.1. New buildings, as well as space additions and lighting retrofits that affect more than one-half of a building’s fixtures, must use lighting controls. Spaces with ceiling-high partitions also must feature individual controls.
For limited-use spaces — such as supply, storage or janitorial closets — a good choice is a digital time switch, which can replace a light switch and automatically turns off lights at a preset time. It works like the electromechanical preset twist timers, except that a push button replaces the twist knob. A digital display shows timer countdown. Operators can turn off lights before the time elapses.
To qualify for the commercial building tax deduction for lighting projects, the interim rules of EPAct 2005 state that projects must meet the 90.1 controls requirements and have bi-level switching.
This requirement has created much discussion and controversy. The National Electrical Manufacturers Association (NEMA) has clarified the requirement by stating that bi-level switching is two discrete levels of light, not including off. All occupied areas, except hotel and motel guest rooms, storerooms, restrooms and public lobbies, must feature bi-level switching.
Managers can achieve bi-level switching through manual or automatic means, which can be as simple as a split-ballasting system with two circuits, each controlled by a separate switch accessible to occupants. Other means of providing bi-level switching include re-wiring alternate fixtures, in-board/out-board switching — two wall switches — high-low step-dimming ballasts, or bi-level switching ballasts.
One bi-level switching ballast on the market enables occupants to toggle between the high and low states by using one wall switch. When the switch is turned on, all lamps light. Turning the switch off and back on in a short time will switch the lighting to the lower setting.
This bi-level ballast can toggle between two lamps and four lamps on four-lamp fixtures, and between two lamps and three lamps on three-lamp fixtures. Fixtures with standard T8 lamps will use 73 watts in the two-lamp setting, 93 W in the three-lamp setting and 110 W in the four-lamp position.
Another available bi-level ballast is a high-efficiency instant-start unit with a built-in power-line carrier control that dims when it receives a signal in response to automated peak signal alerts. Utility system operators trigger facilities that have agreed to shed loads during high-demand periods. Signals come through telephone lines, radios, pagers, cell phones or the Internet. After receiving such a signal, power can be dropped in common-use areas, such as hallways and corridors, by as much as 33 percent.
Research by the Lighting Research Center shows that when organizations provide individual controls, building occupants are more responsible about controlling lights. In one test setting, occupants used 40 percent less lighting energy when given individual control, such as infrared remote controls or personal dimmers.
In small spaces with windows, such as individual offices, managers can use self-adjusting dimming ballasts to provide cost-effective daylight harvesting. These ballasts are equipped with individual photo-sensors that automatically and continuously adjust lamp output to take advantage of available daylight. System operators also can set initial light levels that will compensate for lamp lumen depreciation.
One important technology advance on the horizon is a simple, low-cost, and easy-to-install daylight switch for individual fixtures. This product turns off fixtures where there is sufficient daylight. It could save 30 percent on lighting costs and provide a three-year simple payback. This device should arrive in 2008 after testing is completed.
Take it Outside
One simple way to curtail outdoor lighting costs is to replace inexpensive cadmium-sulfide (CdS) photocells with photocells that use silicon. CdS cells drift, eroding energy savings, but silicon cells do not. Also, one model can turn off lights at some point overnight, saving considerable energy in parking lots.
The second best way to curtail energy consumption and costs with lighting controls is by simply turning lights down. Managers can provide dimming in conference rooms with fluorescent dimming ballasts, allowing the removal of costly incandescent fixtures. Dimming ballasts that respond to wall-box dimmers can be retrofit into fluorescent fixtures and connected to existing incandescent dimmers.
Finally, the promise of wireless lighting controls to greatly reduce installation costs for new systems and allow cost-effective retrofits in existing buildings has not yet materialized with any noticeable market penetration.
In addition to the higher potential for energy savings, wireless control systems have considerable potential for demand-reduction strategies in response to automated signals from a utility. The savings from such demand-response controls will play a more important role as real-time pricing rate structures become more common.
The opportunity for managers is fairly straightforward: Simple lighting controls can reduce lighting costs by turning off or turning down lighting systems.
Beyond that benefit, controls are required to meet the 90.1 and IEEC codes and to fulfill the requirements of the commercial building tax deduction for lighting projects. The question now is not so much when facilities will make the move, but how to specify, install and operate lighting-control technology that best suits each organization’s needs.
John L. Fetters, CEM, CLEP, is president of Effective Lighting Solutions in Columbus, Ohio.