Answers Controlling Lighting with Building Automation Systems . Volume 4 Number 1 May 1997 Introduction • The ability to monitor and control lighting throughout a building or even throughout The potential for substantial energy savings a multi-building facility has made the use of automated lighting • The ability to minimize peak demand, controls such as timers, occupancy sensors, thereby reducing energy costs where and photosensors commonplace in modern utility rate structures are based on peak buildings. Similarly, building automation demand and real-time pricing systems that control heating, ventilation, and air-conditioning (HVAC) have become com- Conventional lighting control systems mon in new construction and are now in- often control equipment in a single room or cluded as part of many retrofit projects; more over a limited area, because they are cen- than half the large commercial buildings tralized control systems, which means that all (averaging 200,000 sq ft) surveyed by the the controlled circuits must be wired to a Wisconsin Center for Demand-Side Research single control panel. The computers used (WCDSR 1995) included a building automa- by these systems are typically dedicated tion system. microprocessors that perform only lighting Building automation systems can also control functions. be used to control lighting; however, high By comparison, modern building automa- initial and maintenance costs, the apparent tion systems are distributed control systems, complexity of these systems, and concerns which means that their computing hardware about the interoperability* of lighting sys- and software are distributed as a network tems and other building systems have lim- that comprises microprocessor-based control ited such applications. The National Lighting modules and standard personal computers Product Information Program (NLPIP) pre- (PCs). The control modules use direct digital pared this issue of Lighting Answers to ex- control technology to communicate with each plain the options, benefits, and potential other and act together as an “intelligent” pitfalls of controlling lighting with building whole. Direct digital control systems are automation systems and to direct lighting extendible virtually without limit, so that all specifiers and facility managers to resources the lighting in a facility can be controlled by for further information. a single, unified system—the same system Building automation system-controlled that also can control and monitor the lighting systems may offer incremental en- building’s HVAC, security, and smoke detec- ergy savings over properly applied timers, tion systems, manufacturing processes, occupancy sensors, and photosensors; in elevators, and more. addition to these savings, which are not usually large, building automation systems offer other benefits: What is a building automation system? A building automation system is a computer • Detailed reports on occupancy and network that integrates the controls of a energy use building’s various electrical and mechanical • Enhanced operation scheduling systems. There are two main techniques for • The ability to share occupancy information implementing a building automation system: with other building systems integrating a number of existing control *Terms in italics are • Diagnosis of lighting system problems systems and creating a new distributed con- defined in the glossary • A wide array of manual control options for trol network to control all of a building’s on p. 7. building occupants and building managers systems. Often strategies for automating building controls combine both techniques. How does a building automation system For example, an existing HVAC control sys- control lighting? tem can be connected to a new distributed control network that controls lighting, secu- A building automation system can control rity systems, and fire alarms. lighting using schedules, manual controls, Building automation systems require com- occupancy sensors, and photosensors, either puters, and thus are only as useful as their singly or in combination. programming. The sophistication of software for these systems varies widely. The simplest Schedules. Much of the energy savings system may merely schedule operation of the produced by a building automation system equipment. A more sophisticated system comes from scheduling the operation of running custom software developed using electrical loads. For instance, the lighting in fuzzy logic may have the ability to learn occu- a building can be programmed so only occu- pancy patterns, so that it can anticipate when pied spaces are lighted during the evening or to turn on devices that require warm-up time, at night. Different schedules can be pro- such as metal-halide lighting systems, manu- grammed for individual circuits or groups of facturing equipment, or copy machines, and circuits (called zones). Each zone also can so that it can adjust the HVAC system accord- have a unique schedule for weekdays, week- ing to the schedules of occupants. ends, or special events. Some systems auto- matically adjust a lighting zone’s schedule to account for seasonal variations in the What is direct digital control? availability of daylight. A building automa- tion system using fuzzy logic could dynami- Direct digital control is the technology used in cally adjust schedules based on typical a distributed control system. Each circuit to occupancy patterns. be controlled or monitored is connected to a direct digital control module or a multi-circuit Manual controls. The availability of manual direct digital control panel which represent controls often is a key factor in occupant nodes on a distributed control network. Unlike acceptance of a new lighting system. Manual centralized control systems, which require controls may also increase productivity by that all nodes be wired to a central hub, each providing a means by which occupants can new direct digital control node can be wired to optimize their work environment to their the nearest node on the network. For network changing needs. A study by Rensselaer Poly- setup, monitoring, data logging, and direct technic Institute’s Center for Architectural control, PCs with a direct digital control inter- Research showed that productivity in an insur- face card can be connected anywhere on the ance office increased 3%, and complaints network as an administration node. about the environment dropped to zero when Direct digital control modules are minia- occupants were given convenient manual ture computers. Each one informs the net- work about the status of the device to which it . is connected, and each one can be pro- grammed to respond to direct commands Figure 1 from other modules or to a change in status of Programmable control pad for DDC any other device on the network. Direct digital manual control control modules are available for any type of Customers of the electric lighting load or sensor; many lighting control utility Central and South- components, including occupancy sensors and west Corporation in photosensors, are available with this technol- Laredo, Texas, use this ogy built-in. Direct digital control modules and bilingual control pad to program the operation of components for other building systems are their air conditioners, also widely available. water heaters, and other The hardware for a direct digital control appliances. Customers system can be installed more easily and faster can set their appliances than that of a centralized control system. to automatically respond when the utility varies the Expanding or modifying the system is also cost of electricity during quick and easy. the day in response to demand. 2 control over the temperature and lighting in the building automation system can turn on their workstations and lighting systems. (Kro- the hallway lights on that floor, adjust the ner et al. 1992). Manual dimming controls can temperature in that office, alert the security also save energy in daylit offices, or where staff that the room is occupied, and even occupants perform tasks requiring low light- send an empty elevator to that floor to pick ing levels for part of the day. up the occupants. Direct digital control modules can be A building automation system can also be connected to existing manual light switches programmed to respond to a signal from an and dimmers. The system can be pro- occupancy sensor by dimming lights rather grammed to let manual controls override than switching them off or by dimming them signals from sensors or to consider the status at first and then switching them off only if the of manual controls and sensors and the time space remains unoccupied for an extended of day in an algorithm when determining period of time, to minimize the likelihood what lighting control commands to send. that occupants will be left in total darkness. A wide variety of specialized manual con- Actual lighting energy savings from occu- trols are also available for direct digital control pancy sensors vary widely from none to al- networks, including control pads with multiple most 80%, but manufacturers frequently cite programmable buttons, multifunction liquid- an average savings of 30% for private offices crystal display panels (such as the one in (Sensors Save A Lot, Field Tests Show, 1995). Figure 1), and hand-held remote controls. Allowing occupancy sensors to also control Interfaces are available that make manual the HVAC system may substantially increase control possible through touch-tone tele- the total savings. phones. PCs with access to the