Lighting Design Lab Articles -Occupancy Sensor Application

Occupancy Sensor Application

Occupancy sensors are "application-sensitive" devices, meaning that most problems in the field are the result of misapplication. Here are some general guidelines that can help with occupancy sensor application:

Calibrate the sensor. The sensor will be provided with manufacturer-default settings for sensitivity to magnitude of motion and time delay before switching the lights off. The default time delay may be from 30 seconds to 15 minutes. Be sure to calibrate the sensor to specific conditions in the space for best performance.

Understand local occupancy patterns. Occupancy sensors generate the greatest savings in spaces where occupancy is unpredictable and/or intermittent.

Line of sight must be maintained between the sensor and the occupant except in the case of an enclosed space with hard surfaces covered by an ultrasonic sensor. Be sure to view sensor specifications to determine the amount of coverage that will be provided to the space by the sensor; this will aid with choosing the number of sensors required to cover an area properly and where to place them.

The amount of motion required to keep the lights on is based on distance between the sensor and the occupant. Ultrasonic sensors are more sensitive at greater distances than PIR sensors.

Avoid conditions that may result in false triggering. Conditions to generally avoid include using an ultrasonic sensor for restricted-coverage areas and high-bay and outdoor applications; setting the ultrasonic sensor to maximum sensitivity so that it picks up small non-human movements in the space; and setting the sensor so that it turns off too quickly or cannot see the occupant, such as bathrooms/stalls. Avoid placing an ultrasonic sensor where it can pick up vibrations and air currents, and placing a PIR sensor where it is exposed to direct sunlight that can trigger it. If a PIR sensor has a line of sight into an adjacent hallway, resulting in false triggers, then simply put a masking label on the section of the lens that can "see" into the hallway to restrict its coverage.

Consider the direction of motion. Ultrasonic sensors are most sensitive to occupants moving towards and away from the sensor, while PIR sensors are most sensitive to lateral motion.

Check the load limits for the sensor selected. Ensure that the load handled by the sensor is within the minimum and maximum limits specified by the manufacturer.

Check with the manufacturer to determine if there is a limitation in compatibility with any other lighting equipment, such as electronic ballasts.

Determine switching’s effect on lamp life. Frequent switching can shorten lamp life, particularly if the lamps are instant start lamps. However, also calculate into the total impact of occupancy sensors the effect of reduced operating hours.

Trial installation. Consider a trial installation to learn more about actual occupancy sensor performance in a given space before full installation. Note that most occupancy sensors include an LED to indicate that the sensor is detecting occupancy/motion.

Commission the system. After installation, set the desired time delay and sensitivity, then calibrate performance by testing the sensors.

Manufacturers of Occupancy Sensors

Space Type	Use Pattern	If...	Then...
Cafeterias or Lunchrooms	Occupied occasionally	Daylighted	Consider daylight-driven dimming or on/off control
Cafeterias or Lunchrooms	Occupied occasionally	Occupied occasionally	Consider ceiling-mounted occupancy sensor(s). Make sure minor motion will be detected in all desired locations.
Classroom	Usually occupied Occasionally occupied	Multi-tasks like overhead projectors, chalkboard, student note taking and reading, class demonstrations	Consider manual dimming
		Occupied by different students and teachers	Consider ceiling- or wall-mounted occupancy sensor(s) and manual dimming. Make sure that minor motion will be detected.
		Lights left on after hours	Consider centralized controls and/or occupancy sensors.
Computer Room	Usually unoccupied	Lights are left on all the time	Consider occupancy sensors with manual dimming. Be sure that minor motion will be detected and that equipment vibration will not falsely trigger the sensor.
Conference Room	Occupied occasionally	Multi-tasks from video-conferencing to presentations	Consider manual dimming (possibly preset scene control)
		Small conference room	Consider a wall box occupancy sensor
		Large conference room	Consider ceiling- or wall-mounted occupancy sensor(s). Be sure that minor motion will be detected in all desired locations.
Gymnasium or Fitness	Usually occupied	Requires varied lighting levels for activities	Consider manual dimming and occupancy sensors. Be sure that the HVAC system will not falsely trigger the sensor.
Hallways	Any	Occasionally or usually occupied	Consider occupancy sensors with elongated throw. Be sure that coverage does not extend beyond the desired area.
Hallways	Any	Daylighted	Consider daylight on/off control
Health Care - Examination Rooms	Occasionally occupied	Different lighting needs for examination	Consider manual dimming
Health Care - Examination Rooms	Occasionally occupied	Small areas	Consider a wall box occupancy sensor
Health Care - Hallways	Usually occupied	Daylighted...	Consider automatic daylight-driven dimming
Health Care - Hallways	Usually occupied	Requires lower lighting level at night	Consider centralized controls to lower lighting levels at night
Health Care - Patient Rooms	Usually occupied	Different lighting needs for watching television, reading, sleeping and examination	Consider manual dimming. Occupancy sensors may not be appropriate
Hotel Rooms	Occasionally occupied	Use primarily in the late afternoon through evening for sleeping and relaxing	Consider manual dimming
Laboratories	Usually occupied	Daylighted...	Consider automatic daylight-driven dimming in combination with occupancy sensors.
Laundry Rooms	Occasionally occupied	Requires high light levels, yet lights are usually left on	Consider occupancy sensors
Libraries - Reading Areas	Usually occupied	Daylight...	Consider automatic daylight-driven dimming
Libraries - Reading Areas	Usually occupied	Lights left on after hours	Consider centralized controls
Libraries - Stack Areas	Occasionally occupied	Stacks are usually unoccupied	Consider ceiling-mounted sensor(s)
Lobby or Atrium	Usually occupied but no one "owns" the space	Daylighted and lights should always appear on...	Consider automatic daylight-driven dimming
		It isn't a problem if lights go completely off in high daylight...	Consider automatic daylight-driven dimming or on/off control
		Lights are left on all night long, even when no one is in the area for long periods	Consider occupancy sensors. Be sure that minor motion will be detected in all desired areas.
Office, Open	Usually occupied	Daylighted...	Consider automatic daylight-driven dimming
		Varied tasks from computer usage to reading	Consider manual dimming
		Lights left on after hours	Consider centralized controls and/or occupancy sensors.
Office, Private	Primarily one person, coming and going	Daylighted...	Consider manual dimming, automatic daylight-driven dimming, or automatic on/off
		Occupants are likely to leave lights on and occupants would be in direct view of a wall box sensor	Consider a wall box occupancy sensor
		Occupants are likely to leave lights on and partitions or objects could hide an occupant from the sensor	Consider a ceiling- or wall-mounted occupancy sensor
Photocopying, Sorting, Assembling	Occasionally occupied	Lights are left on when they are not needed	Consider an occupancy sensor. Be sure that machine vibration will not falsely trigger the sensor.
Restaurant	Usually occupied	Daylighted	Consider automatic daylight-driven dimming
		Requires different lighting levels throughout the day	Consider manual dimming (possibly preset scene dimming)
		Requires different lighting levels for cleaning	Consider centralized control
Restroom	Any	Has stalls	Consider a ceiling-mounted ultrasonic occupancy sensor for full coverage.
Restroom	Any	Single toilet (no partitions)	Consider a wall switch occupancy sensor
Retail Store	Usually occupied	Daylighted...	Consider automatic daylight-driven dimming
Retail Store	Usually occupied	Different lighting needs for retail sales, stocking, cleaning	Consider centralized controls or preset scene dimming control
Warehouse	Aisles are usually unoccupied	Daylighted	Consider daylight-driven dimming or daylight on/off control
Warehouse	Aisles are usually unoccupied	Lights in an aisle can be turned off when the aisle is unoccupied	Consider ceiling-mounted occupancy sensors with elongated throw. Select a sensor that will not detect motion in neighboring aisles, even when shelves are lightly loaded.

Introduction to Occupancy Sensors

Method of Operation

Applications