22 August 2006
5-5.1.2 Non-task-dominant areas. Automatic daylight on/off is more acceptable in
these areas, yet dimming is still preferred. Occupancy sensors in these public areas will
save the most energy, though lights can be turned off with an energy management
system. If occupancy devices allow adequate time, especially in transition areas, then
the lighting is not disrupted during normal hours of operation.
5-5.1.3 Passive infrared sensors detect the difference in heat between a human and
the surroundings. Because of this, the sensor must be able to "see" the entire space
and any obstruction such as partitions, shelves, or cabinets will block detection.
Changes in ambient temperature will also reduce the effectiveness of infrared sensors.
5-5.1.4 Ultrasonic technology relies on high frequency sound waves to detect
movement in the space. This movement could be a person moving, or air movement
created by a person's activity. This type of sensor is therefore appropriate for spaces
that have partitions such as restrooms or open office areas. Such sensors need to be
located so that they do not sense the "false-occupancy" of an air vent or a passer-by in
an adjacent space. Room finishes such as carpeting may absorb the ultrasonic waves
and reduce coverage.
The light source also needs to be considered in designing a control system.
Some sources are more suitable for dimming or switching than others. Dimming and
switching may also affect the life of the lamp. In other cases, undesirable color shift
may occur when a source is dimmed. Table 5-7 outlines some of the issues that need
to be considered in matching control strategies with lamps. In all cases, lighting
controls must be commissioned to optimal operation and user satisfaction.