Selection Of Occupancy Sensors

Pick the right sensor type.

Ultrasonic sensors are more sensitive to movement than PIR devices, but they're also more prone to false triggering. Both will work in the typical office setting if they are installed carefully, as described below. PIR sensors are a better choice in a typical workstation, where the line-of-sight requirement of a PIR sensor can be easily meet, and the PIR's resistance to false triggering gives it an edge over ultrasonic technology.

Install sensors carefully. As is the case for wall- and ceiling-mounted occupancy sensors, the sensors that come with smart power strips are easily visible and can potentially be improperly adjusted, stolen, vandalized, or fooled into perceiving a human presence when a space is unoccupied. For continued energy savings, users should take the following precautions:

• Involve building personnel in planning for the sensors.

• Train maintenance personnel and office occupants to keep sensors operational rather than disconnecting them when problems occur.

• Position sensors carefully so that they only see the area that you want them to see; the biggest cause of false triggering is incorrect sensor positioning.

Decide on an area of coverage. Some smart power strips come with small-range sensors that only sense a presence in the workstation; others cover a wider area and detect the presence of people in the office around the workstation. Choose the latter if you want equipment to turn off less frequently and turn on sooner.

Pick a product with an adjustable time delay. Smart power strip products may come with either adjustable or factory-set time delays that determine how long a period of nonoccupancy must be before the equipment is turned off. A product with an adjustable time delay allows adjustment of the smart power strips to suit individual work habits.

Purchase Energy Star equipment in addition to smart power strips. The Energy Star program, a joint effort of the EPA and the U.S. Department of Energy, encourages manufacturers to produce more efficient equipment and to incorporate low-power sleep modes in many devices. These features can reduce energy use in office equipment to some degree, but they are best viewed as supplements to smart power strips rather than alternatives. That's because not all office equipment is available with a sleep mode (task lights, for example), and even sleep modes use some power, which can be eliminated with a smart power strip. Also, Energy Star features don't work for all situations, such as when manufacturers or equipment users disable Energy Star features.