How to Select Lighting Controls: Where and Why

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 served.
 Areas with intermittent occupancy are well-suited to occupancy sensors. In large, open office areas with many occupants, scheduled switching (“time scheduling”) is often an effective energy-saving strategy. In daylit offices, properly adjusted daylight sensors with dimming ballasts make sense. Because some workers prefer lower lighting levels, bi-level manual switching is another option. Advanced lighting controls can be used for demand limiting to allow building managers to reduce lighting loads when electricity demand costs are high.

Some types of lighting are not well suited to certain controls. For example, daylight dimming and occupancy sensing are not generally appropriate for high intensity discharge (HID) lighting (which requires a delayed re-start), whereas time scheduling is usually a good match for HIDs.

Proper illumination levels depend on the type of work being performed, and on occupant preference. Recommended illuminance levels for offices range from 30 to 60 footcandles (10.8 lux), but the quality of the visual environment can have a substantial impact on the “appropriate” amount of illumination. In well-designed office spaces, with lightcolored surfaces, appropriate task lighting, and careful placement of lights and furniture to avoid glare and shadows, much lower illuminance levels are acceptable, and usually even preferred.

Proper placement and orientation of both daylight and occupancy sensors is essential. Placement of controls should take into account furniture placement as much as possible. Occupancy sensors must be able to sense all occupants to avoid turning off lights while the space is occupied. At the same time, “false-on” incidents can be triggered by an automatic on/off sensor that is exposed to passersby in an adjoining hallway. Daylight sensors that are placed where they are exposed to an amount of daylight not proportionate to the daylight at the desktops being served will not properly control lighting levels (and will likely result in dissatisfied users who may attempt to disable the control system).

Set time scheduling controls so that the switching times and intervals make sense for the occupants and usage pattern of the space. Occupants need to know how to override the schedule easily when needed.

Choose daylight sensors that can be calibrated quickly and easily, and take the time to calibrate them correctly. The dimming adjustment should be easily accessible to the installer and provide an acceptable range of dimming.

Commissioning and calibration of lighting controls are essential if energy savings are to be achieved and maintained. Occupancy sensors with sensitivity set too high can fail to save energy, but occupancy sensors with too low a sensitivity or too short a delay time can be annoying to occupants. Similarly, improperly adjusted daylighting controls can dim the lights too low, causing occupants to override them (e.g., by taping over the sensor), or can fail to dim the lights at all.
Share on Google Plus


Post a Comment

Contact Form


Email *

Message *