Specifying lighting controls: Part 1
Part 1 looks at four common types of lighting controls: panelboards, dimming controls, addressable controls, and relay-based systems.
Lighting control is an effective way to save energy beyond using energy-efficient lighting sources and manual or sensor operated switches. A lighting control system controls multiple luminaires at one central point or it may be modular. This type of system allows local control or communicates with the BAS, and employs energy conservation measures such as daylight harvesting and occupancy sensing. With modern digital communications, the possibilities are essentially limitless, and the integration, operation, and coordination of these systems can become quite complex.
An engineer can use MasterSpec to specify one of four lighting control methods in a commercial or industrial project: a lighting control panelboard, central or modular dimming controls, addressable luminaire controls, and relay controlled circuits. These four don't cover every single type of lighting control, but they are the most common types of lighting controls specified in the United States.
Lighting control panelboards use electrically operated circuit breakers to control lighting. These panelboards can be a standalone or networked system, and they are very similar to standard panelboards, except that they use low-voltage or digital control circuits to operate circuit breakers. The circuit breakers provide the same or similar overcurrent and overload protection to the attached circuits. Note that circuit breakers are not as durable as other lighting control devices, such as relays. Individual luminaires or portions of the circuit controlled by the relays may additionally be controlled by an individual lighting control device, such as a snap switch or photoelectric relay, as long as the switch is properly wired into the circuit controlled by the circuit breaker.
One disadvantage of this control scheme that it only provides on and off control with no dimming capability, while an advantage is that both switch and overcurrent protection are combined into one unit, saving space and cost. This means that they are ideal for applications such as sports lighting or for luminaires that do not need to be dimmed.
Central and modular dimming controls allow the user to control light levels using a control interface. A central dimming system allows on-off control and control of groups or individual lighting levels. It is a hybrid of a wall-box dimmer and a theatrical lighting system. This combination results in a system that allows several different types of control panels and almost unlimited zones, but it requires dimmers to be mounted in remote cabinets and can result in complicated wiring schemes. Modular dimming controls consist of standard components that are combined to provide various dimming control schemes. These systems are not as robust or capable as a central dimming system, but they cost less. Both types of systems are capable of being controlled by or interfacing with a BAS.
Addressable luminaire lighting controls use a digital addressable lighting interface to control lighting. The original standard required separate cabling for a separate control unit connected to a luminaire; modern luminaires can have the control unit as part of the luminaire from the factory and use Cat 6 cable, powerline carrier, or wireless networking to control the luminaire. An advantage is that power may be connected to the luminaire and the luminaire may be controlled via a central system, local addressable switches, or both. Advances in this type of system make it difficult for a drawing or specification to stay current, so the engineer should carefully coordinate with a manufacturer or several manufacturers’ representatives. Of these four lighting control systems, this type offers the most flexibility and expansion potential, but also relies more on the manufacturer to support and maintain the system components than do the other types of lighting control.
A relay-based lighting control system uses a lighting control panel with mechanically held relays for switching the lighting on and off. Many of the characteristics are similar to a lighting control panelboard: the system can be standalone or networked, it can use line or ultra-low voltage for relay control, and the relays only turn the circuits on or off with no dimming capability. Individual luminaires controlled by the relays may also be controlled by an individual lighting control device, such as a snap switch or photoelectric relay, as long as the switch is properly wired into the circuit controlled by the relay. These types of systems are extremely reliable, and can be used for more than lighting control, as most relays are rated for up to a certain horsepower. Most relays have endurance ratings in excess of 50,000 operations at full load.
It should be noted that these four methods all can use similar time, light sensing, or computer control to control lighting. These systems can generate control signals internally by using occupancy schedules or responding to alarms. They can also accept external inputs from manual overrides, daylight harvesting sensors, or the BAS that can trigger action on part of the lighting control system and send information to related control systems, such as power demand control, tenant billing, or the BAS.
Choosing the proper lighting control system will depend on many different factors, some of which include the owner's desire for flexibility, energy savings, individual or group control, sensor or BAS integration, reporting, ease of use, and maintenance. The pros and cons of each type of system should be discussed between the engineer and the design team during programming or design development. The results of that discussion can help the engineer make the appropriate choice of lighting control system and coordinate the information on the drawings and in the specifications.
That's a brief discussion of lighting control as it is covered in MasterSpec. In the next article, we'll discuss some common criteria for specifying lighting control.
Michael Heinsdorf, PE, LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec. He has more than 10 years of experience in consulting engineering, and is the lead author of MasterSpec Electrical, Communications, and Electronic Safety and Security guide specifications. He holds a BSEE from Drexel University and is currently pursuing a Masters in Engineering at Drexel University.