INTEGRATING Fire Alarm Systems with Building Automation and Control Systems By Steven T. Bushby INTRODUCTION ntegrating fire alarm systems with building automation systems can result in many Ieconomic and operational benefits. Such integration requires communication standards and careful design practices. BACnet™ is an internationally recognized communication protocol standard specifically designed for integrating building automation and control systems. Thousands of BACnet systems can be found around the world, and its populari- ty is growing. Newly proposed additions to BACnet make it very well suited for integrat- ing fire alarm systems with building automa- tion systems. SUMMER 2001 Fire Protection Engineering 5 Equilavent BACnet Layers OSI Layers BACnet Application Layer Application BACnet Network Layer Network ISO 8802-2 (IEEE 802.2) Type 1 MS/TP PTP Data Link LonTalk ISO 8802-3 (IEEE 802.3) ARCNET EIA - 485 EIA - 232 Physical Figure 1. BACnet Protocol Architecture Maintaining the integrity of fire alarm In the United States, the National nication. There are thousands of systems when they are integrated with Electrical Manufacturer’s Association installed systems ranging in complexity other building systems requires more (NEMA) Signaling, Protection, and from a single gateway to very large than just communication standards. Communication Section (3SB) has office buildings with top-to-bottom Best design practices, appropriate test- endorsed the use of BACnet as the pre- native BACnet systems, to campus or ing procedures, and modernized build- ferred way to integrate fire alarm sys- city- wide systems linking multiple ing are also needed. tems with other building control sys- buildings. BACnet products include The technology of building automa- tems. The National Fire Protection HVAC controls, lighting controls, tion and control systems has advanced Association (NFPA) is in the process of access controls, and fire detection rapidly over the past fifteen years. revising NFPA 722 to address design systems. Today’s technology provides building issues related to integrating fire alarm Fundamentally, BACnet, like any owners and designers with a rich systems with other building systems. communication protocol, is a set of assortment of options and flexibility. First-generation BACnet fire alarm sys- rules that provide a way to exchange Powerful personal computer worksta- tem products are already available in information. BACnet was designed and tions and intelligent distributed con- the marketplace in the United States optimized specifically to meet the trollers that process complex algorithms and in Europe. These are clear indica- needs of building automation and con- quickly and efficiently characterize tions of interest in integrating fire alarm trol applications, and to convey the state-of-the-art building automation and systems with other building systems data needed by these applications control systems. These advances have and in using the BACnet protocol as a including, but not limited to, hardware taken place across a variety of building means to accomplish that goal. binary input and output values; hard- services including heating, ventilating, ware analog input and output values; and air conditioning (HVAC) control A BACNET OVERVIEW software binary and analog values; systems, lighting control systems, access schedule information; alarm and event control systems, and fire alarm systems. BACnet is a standard communication information; files; and control logic. In spite of these advances, building protocol developed by the American BACnet does not define the internal owners have been frustrated by the Society of Heating Refrigerating, and configuration, data structures, or control inability to bid projects competitively Air-Conditioning Engineers (ASHRAE). logic of the controllers. and to integrate innovative products It has been adopted as a prestandard BACnet is designed to be scalable made by different manufacturers in ways by the European Community3,4 and has from very small, low-cost devices to that best suit the unique needs of their been proposed as an ISO standard. very large complex systems that may facility. The main obstacle has been Today there are over 70 companies involve thousands of devices and multi- incompatible proprietary communication with registered BACnet vendor identi- ple buildings located anywhere in the protocols. The adoption of BACnet1 as fiers. These companies are located in world. It achieves this by combining an the standard communication protocol for North America, Europe, Asia, and object-oriented representation of the integrating building control products has Australia. Commercial BACnet product information to be exchanged, flexible changed the industry and opened the offerings range from gateways that choices for local area network (LAN) door to new innovation in building con- connect proprietary systems to com- technology, an ability to interconnect trol technology and true integration of plete product lines that use BACnet as local area networks, and an ability to previously isolated building systems. the primary or sole means of commu- use Internet protocols (IP) to link build- 6 Fire Protection Engineering NUMBER 11 Unitary Controllers Unitary Controllers Low-Speed LANs High-Speed LANs Low-Speed LANs Field Panel Field Panel Router Field Panel Field Panel Internet Ethernet Ethernet Router Field Panel Field Panel Workstation Workstation Figure 2. A Hierarchical Building Control System Structure ings over wide area networks. The defined, it is necessary to provide a lines or hardwired EIA-232 connections. structure of the BACnet protocol and its way to transfer the information from A key point is that BACnet messages relationship to the Open Systems one place to another. BACnet provides are the same no matter which LAN is Interconnection (OSI) – Basic Reference a choice of five LAN technologies to used. This makes it possible to easily Model5 is shown in Figure 1. meet this need. Several choices are pro- combine LAN technologies into a single BACnet represents the information vided because different building control system. The purpose of the network and functionality of any device by applications must meet different cost layer is to provide a way to make such defining collections of related informa- and performance constraints. A single interconnections. It is common in large tion called “objects,” each of which has network technology cannot meet the systems to combine high-speed (and a set of properties that further charac- needs of all applications. A LAN is high-cost) networks with lower-speed terize it. For example, an analog input defined by a combination of the data (and lower-cost) networks in a single is represented by a BACnet Analog link and physical layers of the OSI system. Such a system is shown in Input object that has a set of properties model. The LAN options available in Figure 2. Figure 2 also illustrates that that include its present value, sensor BACnet are shown in Figure 1. BACnet has wide area networking type, location, alarm limits, and others. The first option is ISO 8802-3, better capability that is implemented using IP. Some properties are required and oth- known as “Ethernet.” It is the fastest In principle, BACnet messages can ers are optional. A device is represent- option and is typically used to connect be transported by any network technol- ed by an appropriate collection of net- workstations and high-end field ogy. This means that technologies that work-visible objects. Once the informa- devices. The second option is ARCNET, have not even been invented yet can tion and functionality of a device are which comes in modestly high speeds be used in the future to convey BACnet represented on the network in terms of or in slower, lower-cost versions. messages, and they can be integrated standard objects and properties, mes- BACnet defines the MS/TP (master- into today’s systems in the same way sages can be defined to access and slave/token-passing) network designed that multiple existing network technolo- manipulate this information in a stan- to run over twisted-pair wiring. gies can be combined today. This lack dard way. This combination of standard Echelon’s proprietary LonTalk* network of dependence on today’s technology is objects and standard messages to can also be used. The Ethernet, ARC- a very important feature of BACnet. access and manipulate their properties NET, and LonTalk options all support a The object-oriented structure also makes up the BACnet application layer. variety of physical media. BACnet also provides a way to add new application Once the information to be defines a dial-up or “point-to-point” functionality to BACnet by defining exchanged and message structures are protocol called PTP for use over phone new objects and/or new application SUMMER 2001 Fire Protection Engineering 7 but these systems have relied on relays release rates in a fire. Using this infor- controlled by the fire alarm system to mation, a fire model in the panel can override the normal controls. This kind predict how the fire will grow and of integration has primarily involved spread. Emergency response personnel constant-volume HVAC systems and can use these predictions to plan a strat- required only on/off control of fans egy for fighting the fire. It could even and dampers to be moved to fully be transmitted by the building systems open or fully closed positions. to fire stations or fire trucks so that Many modern HVAC systems are far planning can begin before emergency more complex. Variable air volume sys- personnel reach the site. This could sig- tems are used to reduce energy con- nificantly improve response time, saving services. This is being done to add sumption. These systems require sophis- lives and reducing property loss. functionality needed for fire alarm sys- ticated control algorithms to operate For all of these reasons and probably tems. Two new BACnet objects, Life either a continuously variable-speed fan others, integrating fire alarm systems Safety Point and Life Safety Zone, have or inlet guide vanes to control the static with other building systems makes a lot been developed.