4 FM quick reads on occupancy sensors
1. Occupancy Sensors Need Not Leave Occupants in the Dark, Shorten Lamp Life
Today's tip comes from James Piper, contributing editor for Building Operating Management magazine: Properly installed occupancy sensors won't leave occupants in the dark or reduce lamp life.
One of the biggest complaints concerning the occupancy sensor is that it can leave occupants in the dark if it falsely believes that the space is unoccupied. Most occupancy sensors work by detecting motion. Once detected, the sensor turns the lights on for a preset amount of time. Each time that motion is detected, the sensor's timer is reset. If no motion is sensed and the timer reaches its preset interval, the lights are turned off. If the space is still in use, the occupants can be left in the dark.
In most cases, the failure to detect occupants is the result of installation or application errors. To be effective the sensor needs to be able to see all or most of the space. Sensors have a limited viewing range and angle. Objects within the space or unusual room configurations can partially block the view of sensors, resulting in false readings. By selecting the right type of occupancy control and by properly placing that control, most false readings can be eliminated. If there still are concerns about leaving occupants in the dark, a single, low wattage fixture can be left switched on at all times to provide backup lighting.
A related concern is that, as a result of their frequent on off cycles, occupancy sensors kill lamp life. While there is no question that this frequent cycling does reduce lamp life as measured by total operating hours, it can actually extend the calendar life of the lamps, particularly in applications where light is only needed a small fraction of the time.
This has been a Building Operating Management Tip of the Day. Thanks for listening.
Lighting Retrofits: Look Closely at Controls
This is Chris Matt, Managing Editor – Print & E-Media with Maintenance Solutions magazine. Today's tip is the energy-savings potential of lighting controls.
Most managers considering lighting retrofits consider only the lighting equipment when, in fact, some of the greatest potential for energy savings comes from controls. At the most basic level, occupancy sensors can save 15-30 percent of a space's lighting energy use if the space has intermittent use throughout the day.
Occupancy sensors can be simple replacements for wall switches, and wireless versions are available that eliminate the need for an electrician to rewire the space. In rooms with daylight, photocells that automatically dim the lights in conjunction with daylight can save an additional 30-50 percent of energy use. By making the leap from devices to systems, managers can tie lighting controls to room schedules, give users individual control of the fixtures in their immediate area, shed load to avoid peak-demand charges from the utility, and set a high-end trim if light levels are higher than needed.
To analyze the opportunities a retrofit presents to an organization, managers will need to plan in advance. A lighting designer can guide managers through the many available options and prioritize the highest-yield returns. A salesperson associated with a manufacturer or distributor primarily is interested in selling their products, so managers need to be aware they will slant their sales pitches to achieve that goal. By comparison, an independent lighting designer who is knowledgeable about current technologies is more likely to look at all potential options.
The designer will learn about the organization and its operations to understand the level of feasible change. They do not have a financial interest in the final equipment selected, so they can make recommendations with the organization's best interest in mind.
The Proper Commissioning of Occupancy Sensors
This is Chris Matt, Associate Editor of Maintenance Solutions magazine. Today’s tip is understanding how to commission your occupancy sensors.
Commissioning begins during the design phase by selecting the right occupancy sensor and locating it correctly on the plans.
During field commissioning, installers should verify that the wiring connecting the sensor or power pack to the power and loads is correct. They also should verify sensor placement and orientation against specifications and drawings. Installation might require two or even three primary adjustments.
The system’s time-delay setting allows installers or in-house technicians to change the amount of time before the sensor turns off lights after it perceives the room is unoccupied. Shorter time delays produce higher energy savings, but they also result in shorter lamp life due to more frequent switching. Longer time delays avoid continual on-off cycles because occupants might enter and leave a space frequently.
The sensitivity setting allows the installer or in-house technician to determine the amount of movement that will trigger the lights to turn on and stay on, or shut off. If the sensitivity level is too high, the sensor might turn on the lights, even though the space is unoccupied. If it is too low, the sensor might turn off the lights, even though the space is occupied.
The light-level setting is available with models that offer a daylight-switching feature. It allows the installer or in-house technician to delay turning on the lights if the room receives enough daylight.
Controlling Lighting Systems
This is Chris Matt, Associate Editor of Maintenance Solutions magazine. Today’s tip is taking control of your lighting systems.
Occupancy sensors have become the lighting control of choice for reducing wasted lighting energy in common-area applications. Sensors can save energy and extend the life of lamps and ballasts. Using occupancy sensors lowers energy use by reducing:
• the kilowatt hours of use
• the power used during the peak demand period, either by automatically dimming lights or turning them off when they’re not needed
• and a building’s internal heat gains; cutting lighting use lowers the building’s cooling needs.
The challenge of effectively specifying occupancy sensors involves selecting the right sensor technology. Examples include: ultrasonic, passive infrared, sound, or combination-dual technology. Standard occupancy sensors also require manual adjustment of their sensitivity and time delay to avoid false triggering.
Sensitivity controls determine the level of movement that will cause the sensor to activate the lighting system. Setting the sensitivity too high increases potential false-on triggering, while setting the sensitivity too low increases the possibility for false-off triggering.
Here’s the bottom line: Using sensors to turn down or turn off lighting systems can reduce energy costs. And when applied correctly, they can improve working conditions and comfort for building occupants.