Consulting-Specifying Engineer - June 2008 - (Page 68)

Equipment Lifecycles Conference room layout Plan view Occupancy sensor PP J S Power pack Junction box Wall switch Low voltage wiring Line voltage wiring Wallwash luminaire Pendant luminaire Dual-technology sensors use both PIR and ultrasonic technologies and keep lighting on as long as one of the technologies detects occupancy. Dual technology sensors are recommended for hard-to-control spaces such as large offices, conference rooms, and classrooms where occupants may be relatively still. Coverage patterns Occupancy sensors are available in a wide variety of coverage patterns of various shapes and sizes. To select a pattern that is the best fit for the application, consider the shape and dimensions of the space, not simply the square footage. Additionally, select sensors that have been tested to confirm coverage of both major and minor motions as prescribed in NEMA Guide Publication WD 7-2000. Sensor layout should facilitate detection of the type of motion anticipated in the space; in many workspaces small motions must be detected to ensure proper operation. Position the sensors above, or close to, the main areas of activity and then add sensors as needed to provide complete coverage. In small offices and spaces up to 12x12 ft, wall switch sensors often work well if the activity can be sensed from the switchbox location. Beware of switchboxes behind doors or in vestibules where sensors might not be able to properly sense the controlled area. In many cases, ceiling sensors will provide the best coverage for the space. When multiple sensors are used, place them so that the coverage patterns overlap slightly. Remember to consider the ceiling height, as this will affect the area that will be covered. Create zones controlled by different groups of sensors to manage lighting in large areas; check energy code requirements when determining zone sizes. c Whiteboard a,b c a,b J Sa Sb Sc PP Isolated relay output to BAS or HVAC system Section Luminaire power wiring J-Box Power pack and J-box above ceiling J-Box PP Low voltage wiring to occupancy sensor Low voltage wiring to power pack Low voltage isolated relay wiring to BAS or HVAC Mount occupancy sensor at same height as bottom of luminaire so sensor's view of room is not blocked Occupancy sensor Wall switch for manual control At the top, the occupancy sensor is positioned in the corner where it has a clear view of the activity in the room, but does not see activity in the adjacent hallway. It is mounted below the ceiling so that the suspended lighting fixtures do not block its view. In the lower image, wall switches provide manual control of the individual lighting loads. Source: Watt Stopper/Legrand 68 Consulting-Specifying Engineer • JUNE 2008

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Consulting-Specifying Engineer - June 2008 Contents Viewpoint Letters News M/E Roundtable No Gambling Allowed on Smoke Control in Las Vegas Be Prepared: Hospital Protections for Catastrophic Events Ready for Retail Commissioning Documents: Necessary Evil Codes & Standards Codes & Standards Case Study Equipment Lifecycles New Products Advertiser Index Green Space

Consulting-Specifying Engineer - June 2008

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