NEWSLETTER

Get Control of Your Lighting

By Joe I. Moreland, PE, CSI (GA PE#26321)

Have you ever been told by a client that you have control issues? If so, you're probably in the good company of many other architects and engineers. Now, before you take offense and start writing an e-mail complaint, let me clarify that we're talking about lighting control issues. No design professional wants to discover that his or her lighting design doesn't function as intended because the controls weren't specified properly. BSD's new Section 26 0923 - Lighting Control Devices covers several devices commonly used for automatic control of lighting, with extensive master note content to help you avoid those lighting control issues (we'll leave the other kind of control issues to Dr. Phil).

Occupancy Sensors

Occupancy sensors are used to control loads by detecting occupancy within the space. They are available with various detection technologies, mounting configurations, coverage patterns, and features, all of which must be considered in order to optimize functionality and flexibility.

In order to properly match occupancy sensors to the application, it is critical to understand how the various available detection technologies work. The occupancy sensor article covers the four most common types of detection technologies:

• Passive infrared occupancy sensors work by sensing movement of thermal energy between zones. They require a clear line of sight in order to detect motion, which can be useful for limiting false activation since complete cut-off of detection coverage is possible. However, the disadvantage is that obstructions can prevent the sensor from detecting motion.
• Ultrasonic occupancy sensors work by sensing frequency shifts in emitted and reflected inaudible sound waves. They do not require a clear line of sight in order to detect motion, which can be useful for detecting motion around objects such as restroom partitions. However, the disadvantage is that complete cut-off of detection coverage may not be possible, so care should be taken to avoid unintended detection such as motion in adjacent spaces reflected through open doors.
• Passive infrared/ultrasonic dual technology occupancy sensors work by using a combination of both passive infrared and ultrasonic technologies. They can provide increased reliability for certain applications that may be more difficult for single technology occupancy sensors. Usually, they are set such that motion detection by both technologies is required to turn the load on, while motion detection by either technology will keep the load from turning off, therefore decreasing the potential for both false activation and shutoff.
• Passive infrared/acoustic dual technology occupancy sensors are similar to the passive infrared/ultrasonic dual technology occupancy sensors described above but work by using a combination of both passive infrared and audible sound sensing technologies.

Occupancy sensors are grouped within the article according to mounting configuration type, which may be either wall switch, ceiling mounted, directional, or luminaire mounted. Within these groups they are organized by detection technology and further by coverage range where applicable. Occupancy sensors may either be line voltage type, which may directly control lighting, or low voltage type, which generally requires accessory power packs to control lighting.

Key optional features to consider include:

• Adaptive technology can help optimize energy efficiency and help reduce false turn-offs by continually adjusting settings according to area usage patterns.
• Integral photocells can help provide additional energy savings by turning load off when adequate daylighting is available.

Outdoor Motion Sensors

Outdoor motion sensors are basically directional passive infrared occupancy sensors that are rated for outdoor use. They are available with or without integral lampholders.

Time Switches

Time switches are used to turn loads on and off according to selected time schedules and may be either digital electronic or electromechanical.

Time switches are commonly available with three basic types of programming capability:

• 24-hour time switches use the same schedule for each day of the week. Products are available with a skip-a-day feature to omit selected days.
• 7-day time switches are capable of different schedules for each day of the week. Products are available with an additional holiday schedule to override the normal schedule for selected days.
• Astronomic time switches are similar to 7-day time switches but are field-configurable to automatically adjust for seasonal changes in sunrise and sunset times.

In-Wall Time Switches

In-wall time switches perform the same function as standard time switches but are designed for installation in a standard wall box, with more limited availability of types and features. Like standard time switches, they may be digital electronic or electromechanical.

In-Wall Interval Timers

In-wall interval timers differ from in-wall time switches in that the load is turned on manually by the user and is turned off automatically by the timer at the end of the preset time interval. They may be digital electronic or spring wound.

Outdoor Photo Controls

Outdoor photo controls are used to turn loads on and off according to available daylight and may be stem-mounted, locking receptacle-mounted, or button type. Locking receptacle-mounted types are most commonly installed on matching receptacles provided in street lighting.

Daylighting Controls

Daylighting controls are used to control loads according to available daylighting within a space. Control may be achieved by switching, stepped dimming, or continuous dimming of loads. Switching controls incorporate a no switching "dead band" between turn-on and turn-off set points to avoid unwanted cycling.

Systems may be designed as open or closed loop. Closed loop systems incorporate feedback by measuring the lighting being controlled, including light from both natural and artificial sources. Open loop systems only measure the incoming natural light source, not the contribution from the controlled artificial lighting source. System components include photo sensors, control modules (switching or dimming), and accessory power packs.

Energy Code Considerations

Most energy codes contain specific requirements for lighting controls that should be considered in the specification and application of devices covered by this section. As always, verify the requirements of the codes that are applicable for your project. Some common considerations that may apply include:

• Occupancy sensors might be used as an exception to the requirement for additional manual controls for lighting reduction in 2009 IECC.
• Occupancy sensors might be used to comply with the requirement for space controls in 2007 ASHRAE 90.1.
• Occupancy sensors might be required to comply with the requirement for occupant sensing devices for classrooms, conference/meeting rooms, and employee lunch and break rooms in 2007 ASHRAE 90.1.
• Occupancy sensors and time switches might be used to comply with the requirement for automatic lighting shutoff in 2009 IECC and 2007 ASHRAE 90.1.
• Daylighting controls might be used to comply with the requirement for separate daylight zone controls in 2009 IECC.
• Time switches and outdoor photo controls might be used to comply with requirements for exterior lighting control in 2009 IECC and 2007 ASHRAE 90.1

LEED Considerations

• LEED (all) 2009, EA Prerequisite 2, requires compliance with 2007 ASHRAE 90.1 mandatory provisions for lighting controls in Section 9.4.
• Points may be earned for LEED-CI 2009, EA Credit 1.2, for the qualified use of daylighting controls or occupancy sensors.
• Points may be earned for LEED (all except EB and CS) 2009, EQ credit 6.1, for qualified lighting controllability.

Other Design Considerations

Electronic fluorescent ballasts may have very large inrush currents that can damage switching contacts of automatic lighting controls if they have not been tested and rated accordingly. Consider requiring lighting controls be tested and rated for compatibility with the expected worst case inrush currents defined in NEMA 410. Similarly, also consider requiring that ballast inrush currents be within those limits.

Consider using programmed-start fluorescent ballasts for fluorescent luminaires controlled by occupancy sensors. Programmed-start ballasts can provide increased lamp life for applications with frequent starting conditions that are typical with occupancy sensors.

It is important to coordinate dimming photo sensors and dimming control modules for daylighting controls with specified dimming ballasts to ensure compatibility.

Conclusion

Since many of your projects likely use at least one of these devices, we expect that you will find our new Section 26 0923 - Lighting Control Devices to be a useful, if not essential, addition to your specifications.