Lighting controls can save energy and reduce peak demand in offices and other facilities. Controls save money while providing user convenience and an improved lighting environment. There are several different kinds of controls. The choice of control type should be based on lighting usage patterns and the type of space.
Occupancy sensors are the most common lighting control used in buildings today. Two technologies dominate: infrared and ultrasonic. Infrared sensors detect temperature changes in a room, and work well where the entire room is within the sensor's field of view. Ultrasonic sensors use high frequency sound, much like bats do, to detect motion (even around corners). Dual-technology sensors use both methods, increasing accuracy and flexibility, but at a higher price. Even though lamp-running life may be somewhat shortened by increased switching due to occupancy sensors, the overall chronological life of lamps is usually extended by the reduced daily burn hours.
Large open office areas work well with simple time scheduling—automatic switching at fixed hours of the day. Overrides allow users to turn on the lights after hours (using wall switches or telephone dial-up codes). Time scheduling can be accomplished with simple time clocks or more sophisticated computer controls. To save more energy, time scheduling systems can be designed so that lights are turned on manually rather than automatically at the beginning of the day, but are turned off automatically at 1 or 2 hours after close of business.
Some people prefer lower overhead lighting levels (especially if daylight is available). Lower light levels are often preferred for computer use, meetings, or tasks that are not visually demanding. Bi-level switching can provide simple manual control. For example, in a typical 3-lamp fluorescent fixture, the outer lamps are switched separately from the middle lamp, allowing the user to switch on one, two, or all three lamps. This low-cost measure is a minimum control requirement in some state energy codes, and can provide a simple means of loadshedding during peak hours if the bi-level lighting circuits are remotely controllable. In rooms where different light levels are needed at different times, such as conference rooms and some private offices, the use of manually-operated dimming controls is a common solution. These controls can either be wall-mounted or, for convenience, use wireless remote controls (like the controls for a TV or VCR).
Automatic daylight dimming, or "day lighting," uses a light sensor to measure the amount of illumination in a space. Then, light output from a dimming ballast is adjusted to maintain the desired level of illumination. The combination of daylight dimming with appropriate task lighting is often very effective. Corridors and open cubicles near windows, particularly those with task lighting, are good candidates for day lighting controls. Private offices with windows can also be equipped with individual daylight sensors. Initial commissioning and calibration of light sensors and controls is critical for effective day lighting, however; poorly calibrated daylight sensors can result in little or no savings, and may annoy occupants.