Lighting controls help make commercial buildings more comfortable, productive, and energy efficient. These controls can either turn lights off when you don’t need them or dim lights so they don’t produce more light than you need. You can use the on-off or dimming functions individually or together to gain even greater benefits. Control equipment ranges from simple timers to complex electronic dimming circuits.
A well-designed control system will provide the right amount of light when and where it’s needed. The system will cut lighting energy use by 5% to 60%, depending on the baseline conditions and the control strategies used. A metastudy performed by Lawrence Berkeley National Laboratory (LBNL) reviewed 240 savings cases described in 88 papers and case studies and summarized the average savings achieved from all major control types (figure 1).
Figure 1: Combining lighting control strategies provides the highest energy saving
Advanced lighting control (ALC) systems, which have a central control system and employ multiple strategies, are growing in popularity. ALCs can improve your maintenance by signaling lamp outages and monitoring output levels to indicate when they fall below desired levels. You can also participate in utility demand-response (DR) programs when you have lighting controls.
LBNL predominately focused on studies that covered fluorescent lighting savings, but LEDs offer the potential for even higher savings, as they’re more efficient than most lighting sources and better suited for controls. However, the total savings (in kilowatt-hours) from controls may not be as high because if you’re already using LEDs, you may be starting from a lower power level to begin with.
Instant response and no cycling effect LEDs respond instantly, and their lamp life isn’t shortened by frequent switching. Fluorescent lamp life decreases when the lamps are cycled on and off frequently; high-intensity discharge (HID) lamps have a long delay time on start-up and restrike.
Dimming capability LEDs are dimmable, and dimming can lengthen the life of LEDs because they run cooler when dimmed. However, you should make sure that they’re paired with a compatible dimmer—an incompatible dimmer can cause power-quality issues such as flickering.
Color controllability LEDs can be designed for a certain color tint, typically referred to as color temperature and expressed in Kelvin (K). LEDs with color temperatures lower than 3,000 K emit a yellowish light and are warmer, while those with color temperatures above 3,000 K emit a bluish-white light and are cooler.
Good-quality LEDs can maintain a constant color temperature as they dim, but some lamps are designed to change color when dimmed. For example, some lamps have cooler color temperature at full illuminance and can change to warmer color temperatures when dimmed to mimic incandescent lamps. In color-tunable LEDs, controls can change the color temperature of lamps to simulate natural light or adjust it for a particular task.
You can achieve dramatic savings when you combine LEDs and controls. Sacramento Municipal Utility District’s Intel Advanced Lighting Controls Project found lighting energy savings of 50% to 90% in more than a dozen projects. About 60% of savings were from light-source upgrades, while 40% were from the addition of controls.
What are the options?
The two major categories of lighting control are on-off and dimming controls. However, you can achieve the highest levels of energy savings by combining dimming, on-off strategies, scheduling, occupancy control, daylight harvesting, personal control, task tuning, and DR. ALCs and building automation systems (BASs) offer a combination of these strategies.
The simplest way to reduce lighting energy consumption is to turn off lights when you’re not using them. All electric lights have manual switches for that task, but building occupants don’t use switches often. The lighting industry has developed various devices to solve that problem.
Occupancy sensors Occupancy sensors typically turn lights on when they detect occupants in a space. The sensors are most effective in spaces that people frequently move in and out of in unpredictable patterns, such as private offices, warehouses, and conference rooms. Occupancy sensors are less likely to be effective in open-plan offices, reception areas, lobbies, retail spaces, or hospital rooms.
Vacancy sensors are similar to occupancy sensors and turn lights off when the space is empty. However, users have to manually turn the lights on after entering the space. In either case, you can install systems that are in partial-on configurations, where the lights turn on at less than full power, and you can then manually turn them up to full output.
The three most common types of occupancy sensors are passive infrared (PIR), ultrasonic, and those that combine the two technologies.
PIR devices are the least expensive and most common type of occupancy sensor. They detect the heat emitted by occupants and are triggered by changes in infrared levels when, for example, a person moves in or out of the sensor’s field of view. PIR sensors are resistant to false triggering and are best used within a roughly 15-foot radius.
Ultrasonic devices emit a sound at a high frequency above the audible range for humans and animals. The sensors are programmed to detect a change in the frequency of the reflected sound. They cover a larger area than PIR sensors can and are more sensitive—but they’re also more prone to false triggering. For example, ultrasonic sensors can be fooled by the air currents produced by a person running past a door, moving curtains, or the on-off cycling of an HVAC system.
You can find hybrid devices that incorporate PIR and ultrasonic sensors. They take advantage of the PIR device’s resistance to false triggering and the higher sensitivity of the ultrasonic sensor. See our guide on occupancy sensors for more information.
Timed switches Timed switches operate either after a time-lapse on triggering or on a programmed schedule. Elapsed-time switches, also called timer switches, typically fit into or over a standard wall-switch box and allow occupants to turn lights on for a predetermined time. Lights turn off at the end of that interval unless the occupants extend the time or switch off the lights sooner. Time intervals typically range from 10 minutes to 12 hours. Timer switches are easier to program, harder to misadjust, and lower in cost than occupancy sensors are.
These switches may be mechanical or electronic (figure 2). Mechanical units are spring-wound kitchen timers connected to a relay, and they’re subject to mechanical failures if used in high-traffic areas. Installers set time intervals on electronic switches using a hidden setscrew. These electronic devices look like conventional toggle switches, so occupants are usually unaware of the presence of the device, reducing vandalism and theft.
Clock switches control lights by turning them on or off at prearranged times regardless of occupancy. They’re most useful in locations where occupancy follows a well-defined pattern, such as stores or streetlights.
Installers will typically place clock switches in electric closets that house lighting power panels. The switches are relatively cheap to install and can control large loads with a single set of contactors.
Clock switches may use mechanical devices—such as motors, springs, and relays—or sophisticated electronic systems that handle several schedules simultaneously. You might need to correct mechanical switches for daylight saving time or after a power failure unless battery backup is available (which can triple the device’s price). Electronic devices include battery backup, and you can easily program them to adjust for shifts to and from daylight saving time or for holiday schedules.
High-end electronic clock switches may include long-life lithium batteries and the capability to receive time signals from the National Institute of Standards and Technology to keep the clocks current. You can integrate electronic clocks with software that lets you monitor system performance, check for overrides, and determine whether the schedule needs to be changed.
Dimming controls save energy by matching lighting levels with human needs. When combined with photosensors that measure light levels, dimmer controls can adjust electric lighting based on available ambient light. Dimming comes in two varieties: stepped and continuous.
Step dimming Step dimming is popular in three-way incandescent lamps. Users can turn individual lamps in a bank of lamps on or off to change light levels (one for low light, two for medium light, and three for full brightness). Newer LED installations have two lighting levels, known as bi-level switching.
Step-dimming ballasts offer more light control and energy savings than nondimming ballasts and cost less than the more-versatile continuous-dimming ballasts (figure 3).
Step-dimming ballasts typically offer two or three lighting levels, and you can use the ballasts with occupancy sensors so that the sensors can dim the lamps rather than turn them off. Dimming reduces on-off cycling, extends lamp life, and increases safety in areas where building managers may be reluctant to turn lights completely off when areas are unoccupied, such as stairwells and hallways. The dimmers also offer a viable way to reduce lighting levels during noncritical hours and to shed peak demand in common areas such as corridors.
Continuous dimming Continuous-dimming controls let you finely adjust lighting levels from bright to dark. They offer more flexibility than step dimming and are used in a variety of applications, including mood setting and daylight dimming. You can use dimming on all lamp types found in commercial buildings (fluorescent, HID, and LED).
LEDs may not work well on existing residential dimming circuits because dimmers and lamps have to be compatible for optimal lamp performance. For example, an LED driver connected directly to a line-voltage incandescent dimmer may not receive enough power to operate at lower dimming levels, and fluctuations in the current may damage the lamp. Manufacturers of LED light fixtures typically publish lists of specific dimmer products tested and approved for use with their fixtures.
You can find more-sophisticated LED dimmers that use low-voltage controls (variable resistors or 0-to-10-volt direct-current [DC] controls) connected separately to the electronic driver. Full alternating-current power is provided to the driver enabling the electronic controls to operate at all times, allowing you to uniformly dim LEDs (typically down to 5% or lower). However, the dimmers may require additional low-voltage wiring for retrofit applications.
Low-voltage-controlled ballasts Low-voltage-controlled ballasts dim fluorescent lights by reducing the amount of voltage sent to the lamp. They’re popular and are the least expensive type of fluorescent-dimming ballast available. Most use a standardized 0-to-10-volt DC signal—a control signal in which the voltage varies between 0 and 10 volts of DC to produce varying light levels—which makes them compatible with a range of sensors, controls, and BASs manufactured by other companies.
Power-line-controlled ballasts Power-line-controlled ballasts work with phase-control dimmers, which dim lights by reducing the time the lamps receive full voltage. They’re similar to standard incandescent dimmers and eliminate the need to run additional wiring since they run signals over existing power lines.
All fluorescent lamp phase-control dimmers can dim incandescent lamps, but not all incandescent phase-control dimmers can dim power-line-controlled fluorescent ballasts. Most manufacturers of power-line-controlled dimming ballasts list compatible phase-control dimmers on the specification sheet or associated documents.
Three-wire power-line-controlled ballasts A third power-line voltage wire connected to a special control switch regulates these ballasts; they can dim to low levels without requiring a separate low-voltage control wire. However, these ballasts are hard to retrofit into an existing installation if the third voltage-level line isn’t already available.
Low-voltage digitally controlled ballasts Low-voltage digitally controlled ballasts use communication protocols that are either open—such as Digitally Addressable Lighting Interface (DALI), LonWorks, and BACnet—or proprietary.
Since each ballast has an identifier (or an address), you can control them individually on a single network from a central location without a dedicated control wire between each ballast and the control point. The central control system and fixtures can communicate wirelessly over a dedicated network or over the existing Ethernet connection in the building.
You can also add conventional low-voltage-controlled dimming ballasts to digital lighting-control systems with special interfaces that connect to DALI systems and convert the DALI commands to standard 0-to-10-volt DC control signals. You can find DALI controls that can interface with most lamp types—including linear fluorescent lamps, halogen lamps, HIDs, and LEDs—and work with wireless communications.
Personal dimming controls, which allow individuals to control light levels in just their work areas, are also becoming available. Controls are located on a fixture mounted near the individual’s workspace. Personal dimming controls reduce energy use and increase satisfaction levels.
HID dimming is more limited because color shifting, reduced color-rendering index (color accuracy), increased flicker, adverse impact on lamp life, and inadvertent lamp shutdown accompany it during line-voltage variations. Electronic dimming ballasts for metal-halide lamps reduce the severity of some of these problems and make HID dimming more efficient.
Panel-level controllers, also called power reducers, lower the circuit voltage upstream of the ballasts and are useful in dimming HID and fluorescent lights. They’re best in overlit situations that have large banks of lights that are switched simultaneously, such as in retail stores, supermarkets, and large open-plan offices. Dimming levels are usually limited to 25% or less.
A BAS (also known as an energy management system) manages lighting similar to a clock switch or dimmer but with additional features. A typical BAS can handle various loads, including HVAC and plug loads, but lighting-only management systems are also available. You can find BASs that combine on-off and dimming capabilities and manage individual ballasts for ultimate flexibility in setting up lighting-control zones.
One common BAS feature is the sweep mode, which automatically cycles lights on or off in one section or floor to signal that lights will soon turn off. Occupants can override the shutdown in their area by pressing a local switch or sending a code to the BAS. Open communication protocols such as BACnet and LonWorks also make it easier for a BAS to communicate with dedicated lighting-control systems, providing more flexibility.
ALCs are becoming more common in commercial buildings. They use multiple control strategies, and you can control fixtures with a central system. Additional features include:
- A graphical user interface that provides a near-real-time view of lighting-fixture status on a floorplan view of the facility
- The ability to modify schedules for each control zone
- The ability to regroup fixtures into a new zone structure
- A range of communication methods, such as software, internet, and smartphone apps
- The ability to track energy use, demand, and savings
- The ability to modify settings from a computer or tablet for occupancy sensors, photosensors, and task tuning
- DR capabilities
The most common wireless control for buildings is the mesh network, where control is split up among the different points in the network (such as sensors, switches, or other addressable devices) so that there are multiple, redundant paths through the network. With a split control, two nodes that might temporarily have no direct link to each other can still communicate. Mesh networks make it possible to cover large distances with limited transmitting power because the nodes can hand off data to each other. They’re also scalable to larger sizes.
Lighting installers can establish a mesh network in many ways, but the leading approach comes from the ZigBee Alliance. Formed in 2002 as an independent nonprofit organization, ZigBee consists of hundreds of companies working together to develop a global open communication standard for low-power, wireless networks. ZigBee’s ultimate goal is to build wireless intelligence into a variety of devices. Although the group is growing rapidly and products are already on the market, the ZigBee approach still needs to prove itself in terms of reliability, scalability, and cost.
Many facility managers are skeptical of wireless systems because they’re concerned about protecting the network and maintaining the batteries needed to power wireless sensors and switches. Battery-free technology is a futuristic approach to overcome this latter issue. Zero-power wireless sensors use energy from the environment—a process known as scavenging—to operate without batteries. They create electrical energy capable of powering network devices using sources such as the kinetic energy from pushing on a switch or the energy from ambient light. The technology is still evolving and there aren’t many zero-power wireless sensors available yet; one example is VTT Technical Research Centre of Finland’s Energy-autonomous wireless sensor networks.
How to make the best choice
Select the control based on how you use the space, and make sure that your selections conform to local code requirements. You should consider occupancy sensors and timers if space use is unpredictable, such as in warehouse aisles, hotel hallways, or any space that’s unoccupied in an unpredictable fashion for more than 30% of the time. Consider timed switches if space use is predictable and not part of a 24-hour operation. Light-sensitive photoswitches and timed switches work well for exterior lighting used on facades, on signs, and in parking areas. If daylight is available, consider dimming systems or multilevel systems with photosensors. In daylit spaces, vacancy sensors will be more effective than occupancy sensors because users will turn on the lights only if needed.
In choosing between step-dimming and continuous-dimming controls, it’s helpful to know how occupants will use the space. Step-dimming controls are more practical in spaces where:
- Sunlight is abundant
- Fixtures are mounted out of occupants’ sight
- Abrupt changes in light levels aren’t distracting, such as in hallways and atriums
In contrast, continuous-dimming controls are best for areas where occupants might see the fixtures (or the lamps within the fixtures) and there is a concern that drastic lighting changes will distract occupants, such as in classrooms and office spaces.
Thanks to increased availability and lower prices, wireless solutions are growing in popularity. They work well in structures such as:
- Small buildings that have been underserved by technology in the past
- Office buildings where high churn rates lead to frequent reconfiguring of space
- Old buildings that are being converted to modern office spaces
Wireless systems have a lower payback period in buildings that are eligible to participate in utility incentives and DR programs.
Select the right type of control for the expected load profile For a space with predictable work hours and limited weekend use, select controls that will reduce peak demand. Occupancy sensors and photosensors will help reduce demand in tenant spaces, and timed switches can do the same in public areas. In a facility with longer working hours, occupancy sensors coupled with manual dimming or multilevel switching can help to reduce wasted energy.
In spaces that are open day and night, use photosensors along with dimming ballasts to cut daytime energy use, and use manual dimming and multilevel switching to account for lighting preferences and cut energy use at night. Manual controls work best in spaces such as gymnasiums or conference rooms that are lit for specific events; manual dimming and multilevel switching are the best energy-saving options in those situations.
Evaluate cost-effectiveness Energy savings will vary depending on the type of space. You can more precisely estimate occupancy by studying occupant patterns or results from data loggers. Scale models or full-scale mockups may help you estimate the savings potential from daylighting.
Once you estimate potential savings, you can use the incremental cost of the controls to calculate a simple payback period or perform a life-cycle cost analysis.
Test system compatibility Each component in a lighting-control system—including ballasts or drivers, controllers, photosensors, occupancy sensors, and switches—must be compatible. It can be tricky when each item comes from a different manufacturer, so do a small-scale test to help sort out compatibility issues before attempting a large installation.
Commission lighting-control systems Almost all lighting controls require commissioning (testing and calibrating) to operate as intended. For occupancy sensors, you should adjust time delays and sensitivity for each workspace. For photosensors in daylighting systems, you need to set the sensitivity for local room conditions. For best results, professionals can commission the systems initially, and you can fine-tune the systems to meet your needs. Periodic recommissioning will ensure you’ve adjusted all settings properly.
What’s on the horizon?
Lighting controls are expected to become more common as wireless technology makes retrofits more cost-effective, changes national and local codes, and encourages the use of sustainable building guidelines—such as the US Green Building Council’s Leadership in Energy and Environmental Design.
The ASHRAE 90.1 building energy-efficiency code increased the requirements for lighting controls. According to the 2013 update, all new-construction buildings require automatic shutoff controls; prior to 2010, that requirement was for buildings larger than 5,000 square feet. The new code also has more standards for daylighting and requires more types of space to use occupancy sensors than the previous version did. Spurred by these trends, control manufacturers are introducing sophisticated new systems that provide whole-building lighting control and monitoring capabilities.
The ability to control LED lighting to produce variable color temperature could also lead to the introduction of a growing number of products that might affect health, education, and productivity.
Who are the manufacturers?
- Acuity Brands
- Current by General Electric
- Delta Controls
- Digital Lumens
- Energy Resources Inc.
- Limelight (a Lutron product)
- nLight (an Acuity Brands brand)
- Osram Encelium
- Philips OccuSwitch
- Schneider Electric
- Synergy (an Acuity Brands brand)
- Wattstopper (a Legrand product)
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