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Occupancy sensors

Occupancy sensors reduce energy waste by taking over light-switch chores. Sensors turn the lights on when they sense someone coming into a room or area, and then turn the lights off some time after sensing the room is empty. These sensors are best suited in spaces that are used infrequently or unpredictably, such as conference rooms, private offices, classrooms, storage areas, and bathrooms. Sensors can be mounted on the wall just like a light switch or installed in the ceiling.

Occupancy sensors reduce energy waste as changing room temperature by controlling hvac equipment.

Generally speaking, there are three types of sensors: motion-detecting (ultrasonic and microwave), heat-sensing (infrared), and sound-sensing. The area to be lit and the types of surfaces in the space will determine which sensor is most effective

Passive infrared (PIR) or ultrasonic sensors. PIR sensors are the most common type and are able to "see" heat emitted by occupants. Triggering occurs when a change in infrared levels is detected, such as when a warm object moves in or out of view of one of the sensor's "eyes." PIR sensors are quite resistant to false triggering. They are best used within a 15-foot range for two reasons: There are potential "dead" spots between their wedge-shaped sensory patterns that get wider with distance (see Figure 1) and, being passive, they do not send out any signal; instead, they depend on the intensity of the heat output of the moving part of the subject, which drops with the square of the distance

Occupancy sensors reduce energy case Ben Franklin Elementary School
Michigan's Federal Facilities Case  
Northwest Elemantary School Case  
Fellsmere Elemantary School Case  
Selection Of Occupancy Sensors  
A common thread in successful lighting control projects is the high degree of involvement by the building owner. That’s because the benefits of controls — from reduced energy costs to improved productivity — appear only after construction is complete and the space is occupied. But while the space is being built or renovated, funds designated for lighting controls can be a tempting target. It is often up to the building owner to defend the investment in lighting controls against misguided value engineering, cost cutting or construction overrides.

That’s not to say that the building owner has to adopt a “money is no object” attitude toward lighting controls. Even for owners that identify energy savings as a project priority, first costs remain an important issue. That was the case in the construction of the Wal-Mart in City of Industry, Calif. Wal-Mart designated the facility as an Environmental Demonstration Store that could educate the public by example about the benefits of energy-efficient technologies and environmental issues. To that end, the goal of the project was to use an integrated design that beat California’s Title 24 energy standard by at least 25 percent. To achieve that goal, Wal-Mart was open to the use of controlled lighting, but the company wanted to be sure the design was cost-effective.

A collaborative design effort was the key to meeting energy and first-cost goals. Daylighting was a critical element of the design, which used special skylights and continuous dimming controls to respond automatically to daylight levels.

Testing conducted by the team showed that substantially less lighting was needed at night than was normally used. And the team found other savings that could help offset the investment in energy-efficient technologies. For example, the team determined that a drop ceiling wasn’t a necessity; removing it from the design saved $68,000.

How did the lighting design measure up at the bottom line? Lighting energy was cut by 47 percent from Title 24 requirements for 24-hour operation. Payback is estimated at less than three and a half years, excluding the photovoltaic panels used on the project.

Another reason that building owner involvement is crucial is that the owner has to live with the lighting controls. If the controls aren’t well-designed and properly adjusted, occupants may override or disable them. The controls have to be properly tuned to assure that cost and other benefits are achieved.



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