By William and Patti Feldman
While facility owners and managers have, for many years, had to grapple with the needless waste of keeping lighting in buildings turned on, even when areas and rooms are unoccupied, few have made the leap to install occupancy sensors in their facilities. Instead, they have woefully had to contend with the high utility bills that result from having lights working all day and night, or play policeman and remove tape, wedges or other jury-rigs that renters commonly use to override mechanical timers that are installed to control lighting.
Recognizing that occupant-responsive lighting controls resonate advantageously on the bottom line, Ron Urban, owner and manager of Electrical Concepts and Construction Inc., a New Jersey-based electrical-contracting firm that specializes in design/build work for the self-storage industry, suggested these devices to several clients as part of the electrical installation he performs for new construction projects. These devices automate on/off light switching to correspond to actual occupancy patterns throughout a building. Urban cites two benefits: First, facility owners/managers save money year round on energy costs; second, they simultaneously provide tenants with automated, safe, secure lighting throughout all parts of the facility.
In the six occupancy-sensor installations covering more than 600,000 square feet of self-storage space that Urban has performed to date, he installed state-of-the-art occupancy sensors from Leviton Manufacturing Co. of Little Neck, N.Y. These were typically installed in place of manual timers. "No one likes being left in the dark," notes Urban. "Occupancy sensors that reliably jump-start lighting in the nick of time are a great way to avoid the potential hazard of someone entering a darkened area and having to grope for a light switch.
"The renter doesn't have to juggle bundles or put down bulky items to turn on a switch," Urban points out. "And without any action on the part of the renter, the device saves energy by turning lighting off after a specified period, once movement is no longer detected in the area."
The intent of occupancy sensors is to monitor an area or room for human presence and turn lights on automatically when the area is occupied and off once the person has left. There are two types of sensor technologies: passive infrared (PIR), which requires an unobstructed view of the occupant, and ultrasonic (US), which relies on frequency changes. Both are effective control solutions in locations with infrequent occupancy such as offices, storage areas, utility closets or restrooms. Technical preference of one sensor over another depends upon room layout and environmental factors, such as what type of equipment, obstructions, or heating and cooling devices are present.
PIR sensors react to the movement of a human body as a heat-emitting source in a direct line of sight or "field of view" and would be a good match for an entryway, hallway, office or open space; however, they may not work well in a space such as a restroom, where the sensor's field of view could be obstructed by a stall or partition. In this instance, an ultasonic sensor might be the better choice, since it does not depend on a direct line of sight.
Ultrasonic sensors continually generate high-frequency sound waves beyond the capacity of human hearing, in the 25kHz to 40 kHz range, which means they that bounce off everything in their range. These sensors monitor changes in the return time of the reflected sound waves, and turn lights on when they sense a change in frequency. Because they can detect motion behind fixed objects in a room, they are suited to enclosed areas and are a versatile choice for installation throughout a storage facility.
In storage facilities, where space is occupied by people only sporadically, annual electrical savings for lighting usage can quickly supercede the cost of the sensors. (EPA figures indicate that first cost makes up only about 8 percent to 9 percent of the whole cycle cost of a lighting system, with maintenance responsible for about 1 percent to 2 percent and energy consumption responsible for the remaining 90 percent.) Furthermore, occupancy sensors have been shown to extend usable lamp life and the time between lamp replacement, minimizing maintenance costs. In addition, air-conditioning costs are also lowered because less heat is generated from lamps and ballasts that are turned off when they don't need to be on.
Benefits of Using Sensors
Urban says he typically installs the sensors in indoor, multi-floor facilities, using as many as 30 to 50 devices throughout a facility. "Automated lighting control enables users of the self-storage facilities to have their hands free while unloading or loading their equipment, cartons, files and furniture," he says. "We have determined that occupancy sensors are a valuable asset to the owners because the lights are on only when they need to be.
"A secondary benefit of occupancy sensors is that renters were taping up timer switches to keep them on so that they didn't run the risk of having the lights in the hallway go out while they were inside the building. The occupancy sensors, which go on immediately, eliminate the potential hazard of someone getting hurt in a darkened area while looking for a light switch."
Today, the use of sensors is becoming increasingly popular in self-storage facilities. "From my experience, I see that all the big players are installing them. We are incorporating the occupancy sensors into our design and having tremendous results with our customers, who are very happy," Urban says.
Occupancy sensors also work well in both new construction and in retrofit projects. In fact, savings may be biggest for owners of self-storage facilities that were converted for that purpose. Typically, owners of converted facilities will leave the lighting fixtures in place or move them around, but they leave the lights on all of the time. If the ceilings in the hallways are higher than those typically found in a building constructed for self-storage, and the fixtures and lamps are not energy efficient, that much more lighting will necessarily be used. All that lighting remaining on for intermittent visits translates into a lot of wasted energy consumption. A retrofit with occupancy sensors can save owners a bundle on energy expenditures, while helping to avoid the possibility of a personal-injury judgment resulting from the hazards of poor lighting.
William and Patti Feldman write for magazines, newspapers and corporations on industry-related trends and products. They can be reached at [email protected], or call (914) 238-6272.
Leviton Manufacting Co. is a privately-held manufacturer of wiring devices switches and receptacles, lighting controls, surge- protective devices, personnel-protection products, voice/data products and a wide range of connection products.