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 popularity is growing. Newly proposed additions to BACnet make it very well suited for integrating fire alarm systems with building automation 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. The Life Safety Point pressure in the supply air duct. Variable- of sense. The technology is already being object represents the features of an air volume boxes control the airflow driven in that direction by market forces. individual detection or enunciation from the supply duct into individual device. The Life Safety Zone object rep- rooms by modulating dampers. The OTHER INTEGRATION ISSUES resents the status of a collection or control algorithms for these systems are “zone” of life safety devices. When complicated and require interlocks and Several important integration issues these objects detect an alarm, the alarm safeties to prevent overstressing duct- must be addressed if these potential status latches until a reset command is work in the event that dampers do not benefits are to be realized. The primary executed. A new application service open when fans are turned on. Smoke concerns are ensuring the integrity of has also been developed that provides management is much more complicated fire alarm systems in emergencies and a way to reset latched alarms and to with these systems and outside of the isolating them from interference caused silence annunciating devices. All these capability of most fire alarm systems. by failures of other building systems, additions were developed with assis- What is needed is a way for the fire meeting code and Underwriters tance from the fire alarm industry and alarm system to command the HVAC Laboratory (UL) listing requirements, have been approved by the BACnet control system to enter a smoke control and regulating and tracking human committee. They are currently undergo- mode and let the HVAC controllers responses to alarms and trouble ing a public review process and are manage the equipment. conditions. expected to be approved as part of the New sensors are being developed Maintaining the integrity of the fire BACnet standard.6 that can recognize various contaminants alarm system and protecting it from More detailed information about in the air that can represent a fire signa- failures in other building systems are BACnet concepts and structure may be ture or a hazardous contaminant that primarily a matter of system design found elsewhere.7 There is also tutorial poses a life safety threat. In an integrat- practice. Today this is being handled by information and an extensive bibliogra- ed system, these sensors could be used using a gateway to isolate the fire alarm phy available on a Web page main- by the HVAC control system to control system from outside interference. All tained by the BACnet committee ventilation rates with no adverse impact components of the fire alarm system (www.BACnet.org). on their life safety functions. Multiple reside on one side of the gateway and uses for the same information will communicate using proprietary proto- WHY INTEGRATE FIRE ALARM make it more cost-effective to imple- cols in the same way that they did SYSTEMS WITH OTHER BUILDING ment new sensor technology. before BACnet. The BACnet gateway SYSTEMS? In some buildings, access control sys- provides a way for other building systems monitor the location of building tems to get information from the fire There are many reasons for integrat- occupants. Providing access to this alarm system but protects it from inter- ing fire alarm systems with other build- information to the life safety systems ference from outside. This provides the ing automation and control systems. could be very helpful in an emergency. necessary protection, but it also limits Examples include smoke control, single- Emergency response personnel would the integration possibilities. seat access to building information, easi- know where to look for occupants who An alternative approach is to develop er maintenance, sharing sensor data, need to be evacuated. They could also best design practices for constructing obtaining information about the location reduce the risk to themselves by avoid- networks of integrated systems. By of people during an emergency, and ing dangerous areas where no people appropriate selection of network tech- providing infrastructure for new tech- are present. nology and appropriate use of routers nology to improve performance and Research is now underway at the and bridges to filter traffic, interference safety. National Institute of Standards and problems and concerns about guaran- Fire detection systems have been Technology (NIST) to develop a new teed access to network bandwidth in integrated with door locks and with generation of smart fire alarm panels an emergency can be effectively elimi- HVAC fan and damper controls for that can make use of sensor data from nated. Business network systems com- smoke management for several years, an integrated system to calculate heat monly use these techniques today, and

SUMMER 2001 Fire Protection Engineering 9 there is no reason why they cannot be listed fire-detection devices. The testing they are based on performance criteria applied to building automation systems. and listing procedures need to be instead of prescriptive requirements. Having fire alarm systems tested by updated to recognize this reality. By In fire alarm systems, it is very impor- UL and listed for their intended purpose combining good design practices with tant to ensure that only authorized per- is an expensive and time-consuming tests that ensure the integrity of the fire sonnel can silence alarms, reset alarms, practice. It is unrealistic to expect man- alarm system under conditions that can and perform other operations that sig- ufacturers of other building automation occur if the design practices are fol- nificantly affect the performance or sta- devices to absorb this expense when lowed, safety concerns can be satisfied tus of the system. Traditionally this has their products are not directly involved without sacrificing the benefits of inte- been accomplished by having dedicated in detecting or responding to a fire just gration. In some locations, building fire system workstations that provide because they can communicate with codes may need to be modified so that the operator with capabilities that are assigned when the operator logs in. In an integrated system, there may be many workstations with the ability to send messages to fire alarm system components. Fire alarm panels need to be protected from accidental or inten- tional disruption from other devices or workstations in the building. BACnet provides mechanisms for authenticating messages but they are not widely implemented. This is another design issue that needs to be addressed.

INTERNATIONAL STANDARDS ACTIVITIES

As stated before, BACnet has been adopted as a standard in the United States and as a prestandard in the European Community. The Internation- al Organization for Standardization (ISO) Technical Committee 205 is delib- erating the adoption of BACnet as a world standard. This is being done as part of the activities of Working Group 3, Building Control System Design. The participants in this activity include rep- resentatives from the United States, Europe, Japan, and Australia. BACnet is now at the “committee draft” (CD) stage and is expected to advance to the “draft international standard” (DIS) stage soon. The ISO activities are being coordinated with the ongoing maintenance of BACnet in the United States. The inten- tion is to incorporate into the U.S. standard any additional features needed to obtain international acceptance of the protocol. It is also expected that any additions that come from the continu- ous maintenance process in the U.S. will be incorporated into the ISO standard. An effort is being made to coordi- nate BACnet testing and certification programs in Europe and the U.S. There is a strong international consensus that it is in everyone’s interest to be able to freely market BACnet products anywhere in the world. A common stan-

10 Fire Protection Engineering NUMBER 11 dard and reciprocal certification recogni- National Fire Protection Association, 6 Addendum c to ASHRAE 135, First Public tion are critical if this is to happen. Quincy, Massachusetts, 1999. Review Draft, 2000. American Society of Heating, Refrigerating, and Air- There are a variety of important rea- 3 ENV 1805-1: European Committee for Conditioning Engineers, Atlanta, Georgia. sons for integrating fire alarm systems Standardization. with building automation systems. 7 Bushby, S. T., “BACnet,™ a standard 4 ENV 13321: European Committee for communication infrastructure for intelli- These include smoke control, single- Standardization. seat access to building information, eas- gent buildings,” Automation in Con- ier maintenance, sharing sensor data, 5 ISO 7498, Information Processing Systems struction 6 (1997). Elsevier, pp. 529-540. – Open Systems Interconnection – Basic obtaining information about the loca- Reference Model, International For an online version of this article, go tion of people during an emergency, Organization for Standardization, 1984. to www.sfpe.org. and providing infrastructure for new technology to improve performance and safety. A standard communication protocol is a critical infrastructure com- ponent to make this integration possible. BACnet is such a protocol, and it is gaining popularity around the world. More than just communication standards need attention. Systems must be designed and maintained in ways that will assure the integrity of the fire alarm system even when other components of the building automation system fail. It is also necessary to design the system so that bandwidth is available to the fire alarm system when an emergency arises. Best practice design guidelines can meet these needs. UL testing and listing procedures need to be updated to address open integrated systems. In some cases, building codes may need to be revised to performance-based approaches. Market forces are already pulling the industry in the direction of integrated systems. As new technology is developed that adds capabilities because of the integration, the pressure to integrate systems will grow. The end result will be buildings that are easier to operate and are safer for the occupants.

Steven Bushby is with the National Institute of Standards and Technology.

* Certain trade names and company products are mentioned in the text in order to specify ade- quately the equipment used. In no case does such identification imply recommendation or endorsement, nor does it imply that the products are necessarily the best for the purpose.

REFERENCES

1 ASHRAE 135. BACnet – A Data Communica tion Protocol for Building Automation and Control Networks. American Society of Heating Refrigerating, and Air-Conditioning Engineers, Atlanta, Georgia. 2 NFPA 72. National Fire Alarm Code.

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