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BACnet BasicsBen H. Dorsey IIIVP, Marketing & CommunicationsKMC Controls, Inc.

Presentation TitleName & Company of PresenterPreviewBACnetthe standardBACnetthe communityBACnetand you2

CautionBACnet is BIG3

Part 1BACnetthe standard

What is BACnet?A bookAn open standardA data communications protocolAn acronym: Building Automation and Control NetworksA means of integrating building systemsA way of life!

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So . . . BACnet is a data communications protocol and an agreed-upon set of rules for creating interoperable networks of building systems.6

Encompassing . . .Building Automation Systems (BAS)HVAC Central Plant (Chillers, Boilers, Large Air Handlers)LightingPerimeter and Object SecurityFire and LifeSafetyElevatorsThe integration of all of the above.7Who did it?A working group (standard project committee) of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).Began work in 1987 under tremendous opposition (some said it would NEVER be done).Published as a standard in 1995.Supported and maintained by ASHRAE Standing Standard Project Committee 135.8

Its Alive!!!By design, the standard is under continual revision.First published in 1995.In recent times, most manufacturers products have been designed to the 2004 and 2008 versions of standard.9

Not a Reactive ProcessAddenda are issued as the committee works.Public review and comments are mandatory and common.So, for example, when 2008 was issued, it consisted of 2004 + previously issued addenda. (No surprises.)10

What the Standard DefinesIn essence, the standard defines the messages that devices exchange and how they are delivered.11messagetransport

Further . . .The rules of the protocol apply toElectrical signalingAddressingNetwork access (master/slave, peer-to-peer)Error checkingFlow controlMessage sequencing, segmentation, checkpointing Presentation format (compression, encryption)Message format12Source: Mike Newman, BACnet pioneerAnother Pyramid?13The protocol can be viewed as a matrix of layers.Properties14The nucleus to the BACnet atomthe smallest piece of BACnet informationProperties can be read and written.Properties can provide command control.They consist of names and values.

PropertiesExample: high_limit = 78.0The standard requires some properties; other properties are optional; still others can be proprietary.Required properties must be implemented for each object type.Optional properties do not have to be implemented, but if they are, they must conform to the specification.15Property IdentifiersProperty types 0 511 are reserved as standard.166 of these are currently defined in the BACnet specification.Property types above 511 are proprietary and unique to the vendor.The Vendor ID property is used to identify the manufacturer.16Objects17Objects are the fundamental building blocks (atoms) of the standard.Objects represent data that originates in physical inputs, physical outputs, or software processes. Each BACnet Object possesses a number of properties.

Object TypesBinary InputBinary OutputBinary ValueAnalog InputAnalog OutputAnalog ValueMulti-state InputMulti-state OutputMulti-state ValueAveragingPID LoopTrend LogCommandCalendarScheduleLife Safety ZoneLife Safety PointNotification ClassEvent EnrollmentProgramFileGroupDevicePulse ConverterAccumulator18The standard specifies 25 types of objects:

Presentation TitleName & Company of PresenterAccumulator and Pulse Converter added in last revision. Use in energy metering & monitoring applications such as gathering data for peak load management or billing management.ObjectsVendors can implement proprietary object types.When they do so, they use standard data types to promote interoperability.19

Object IDsNumerical identifier that combines object type and instance number.Object types 0 127 are reserved to identify standard BACnet objects.Object types 128 1023 are used to identify proprietary objects.20

Object IDsBACnet devices will support any mixture of object types up to a limit of 4,194,303 instances.Object IDs are typically referred to in this manner:Analog Input, 521ObjectsSummary Objects standardize the organization of data to facilitate the exchange of data between different vendors products.22

Devices23There are six device types or profiles specified by the standard:Operator Workstation (B-OWS)Building Controller (B-BC)Advanced Application Controller (B-AAC)Application Specific Controller (B-ASC)Smart Actuator (B-SA)Smart Sensor (B-SS)Presentation TitleName & Company of PresenterB-OWS: the operators window into the BACnet system. Scope of the standard defines only operation of system. May be used for configuration activities beyond the scope of the standard. It is not intended to perform direct digital control.

B-BC: a general-purpose, field programmable device capable of carrying out a variety of building automation and control tasks.B-AAC: A control device with limited resources relative to the B-BC. It may be intended for specific applications and supports at least some degree of programmability.B-ASC: A controller with limited resources relative to the B-AAC. It is intended for use in a specific application and supports limited programmability.B-SA: a simple device with limited resources intended for a specific application.B-SS: A simple sensing device with very limited resources.Services24Think of BACnet services as the messages that BACnet devices send to each other.Some services read and write properties of one or more objects.Other services send notification of alarms or special events.Still other services read and write files.ServicesBACnet services follow a Client-Server model.A BACnet client is a device that requests a serviceA BACnet server is a device that performs a service25

Categories of ServicesAlarm and EventRouting & event notificationFile AccessAccessing & manipulating files contained in devicesObject AccessRead and write properties Create and delete objectsManipulate lists of dataRemote Device ManagementRemote monitoring and control of devicesVirtual TerminalUsed by a client user to establish a connection to an application program server in another BACnet device.26ServicesReadProperty27

We wish to read the present value for an analog input called SPACE_TEMPService= ReadPropertyObjectIdentifier = (Analog Input, Instance 5)PropertyIdentifier = Present_ValueOperator Workstation(client)

MS/TP AAC(server)Service= ReadPropertyObjectIdentifier = (Analog Input, Instance 5)PropertyIdentifier = Present_ValueValue = 72.3Assuming the target machine can locate the object with this ID and the requested properties, the result would be:The result indicates that the present value of SPACE_TEMP is 72.3Source: ANSI/ASHRAE Standard 135-2004, page 494Presentation TitleName & Company of PresenterBIBBS28BACnet Interoperability Building BlocksBIBBS are collections of servicesBIBBS define 5 areas of interoperability:Data SharingAlarm and Event ManagementSchedulingTrendingDevice and Network ManagementBIBBSData Sharing BIBBSDescriptionB-OWSB-BCB-AACB-ASCB-SAB-SSDS-RP-A (read property)DS-RP-BDS-RPM-A (read property multiple)DS-RPM-BDS-RPC-A (read property conditional)DS-RPC-BDS-WP-A (write property)DS-WP-BDS-WPM-A (write property multiple)DS-WPM-BDS-COV-ADS-COV-BDS-COVP-ADS-COVP-BDS-COVU-A (COV, unsolicited)DS-COVU-B29Alarm & Event Management BIBBSDescriptionB-OWSB-BCB-AACB-ASCB-SAB-SSAE-N-A (notification)AE-N-I-B (notification, internal)AE-N-E-B (notification, external)AE-ACK-A AE-ACK-BAE-ASUM-A (summary)AE-ASUM-BAE-ESUM-A (enrollment summary)AE-ESUM-BAE-INFO-A AE-INFO-BAE-LS-A (life safety)AE-LS-B30Scheduling & Trending BIBBSDescriptionB-OWSB-BCB-AACB-ASCB-SAB-SSSCHED-ASCHED-I-B (internal)SCHED-E-B (external)31DescriptionB-OWSB-BCB-AACB-ASCB-SAB-SST-VMT-A (viewing & modifying)T-VMT-I-BT-VMT-E-BT-ATR-A (automated trend retrieval)T-ATR-BDevice & Network Management BIBBS(1 of 2)DescriptionB-OWSB-BCB-AACB-ASCB-SAB-SSDM-DDB-A (dynamic device binding)DM-DDB-BDM-DOB-A (dynamic device object)DM-DOB-B DM-DCC-A (device communication control)DM-DCC-BDM-PT-A (private transfer)DM-PT-BDM-TM-A (text message)DM-TM-BDM-TS-A (time synchronization)DM-TS-B or orDM-UTC-A (UTC time synchronization)DM-UTC-B (UTC time synchronization)DM-RD-A (reinitialize device)32Device & Network Management BIBBS(2 of 2)DescriptionB-OWSB-BCB-AACB-ASCB-SAB-SSDM-RD-BDM-BR-A (backup & restore)DM-BR-BDM-R-A (restart)DM-R-BDM-LM-A (list manipulation)DM-LM-BDM-OCD-A (object creation & deletion)DM-OCD-BDM-VT-A (virtual terminal)DM-VT-BNM-CE-A (connection establishment)NM-CE-BNM-RC-A (router configuration)NM-RC-B33BIBBs Summary Example: B-BCData SharingAbility to provide the values of any of its BACnet objectsAbility to retrieve the values of BACnet objects from other devicesAbility to allow modification of some or all of its BACnet objects by another deviceAbility to modify some BACnet objects in other devicesAlarm & Event ManagementGeneration of alarm/event notifications and the ability to direct them to recipientsMaintain a list of unacknowledged alarms/eventsNotifying other recipients that the acknowledgement has been receivedAdjustment of alarm/event parametersSchedulingAbility to schedule output actions, both in the local device and in other devices, both binary and analog, based on date and timeTrendingCollection and delivery of (time, value) pairsDevice & Network ManagementAbility to respond to queries about its statusAbility to respond to requests for information about any of its objectsAbility to respond to communication control messagesAbility to synchronize its internal clock upon requestAbility to perform re-initialization upon requestAbility to upload its configuration and allow it to be subsequently restoredAbility to command half-routers to establish and terminate connections34Transport OptionsBACnet IPBACnet Ethernet (8802-3)Master Slave/Token Passing (MSTP)ARCnetLonTalkPoint-To-Point (PTP)35

Presentation TitleName & Company of PresenterEquivalent to the Data Link and Physical layer of the OSI protocol stackTransport ComparisonBACnet IPPopular, fast. No real performance difference between this and 8802-3.Use BBMD or PAD router to get across an IP router.Broadcast issues.BACnet 8802-3Popular, fast. No real performance difference between this and IP.Cannot get across IP routers.MSTPVery popular, especially as a low-level bus technology for AACs and ASCs. Uses EIA-485 signaling over twisted pair wiring.Lower performance.36Presentation TitleName & Company of PresenterBBMDBACnet IP Broadcast Management DeviceExtend a BACnet IP network beyond a single IP subnetSupports BACnet IP onlyOne-hop BBMDTwo-hop BBMDForeign Device Registration

PADPacket Assembler Disassembler (PAD) RouterA PAD router receives traffic intended for a remote subnet and repackages the message such that it can pass through the router.A companion PAD router receives the message, unpacks it, and retransmits it on to the target network.Each PAD router must know the IP address and port number of its companion.

BACnet Layers vs OSI Layers37Standard OSI Reference ModelApplicationPresentationSessionTransportNetworkData LinkPhysicalEquivalent OSI LayerApplicationNetworkData LinkPhysicalBACnet LayersBACnet Application LayerBACnet Network LayerISO8802-2 (IEE 8802.3)Type 1Source: ANSI/ASHRAE Standard 135-2004, page 9ISO8802-3 (IEE 802.3)ARCNETLonTalkMS/TPEIA-485EIA-232PTPAuxiliary DevicesRoutersUseful when networks using different BACnet transport options need to exchange data.*38

Operator Workstation on BACnet IP network

Router BACnet MSTP Controller Network

*This concept is referred to as Internetworking.Presentation TitleName & Company of PresenterHalf routeralso used in some BACnet applications. Basically a trunk in IT terms. It is a node or device that participates as one partner of a serial, point-to-point (PTP) connection. Often used for temporary connections. It is possible, with a PTP driver, for the configuration or OWS software to act as a half router.Auxiliary DevicesGatewaysUseful when devices on a BACnet network must exchange data with devices on a non-BACnet network.*39

BACnet network

Gateway Proprietary Network*This is also Internetworking.

So, whats the difference?A router is really a pass-through device. It doesnt change the form or content of the message but just the packagingmuch like repackaging a standard USPS letter for sending via Fedex. A gateway has to translate and is inherently more complex. It opens the letter, translates it into a second language, and puts it back into some sort of envelope and sends it on.40Source: Mike Newman, BACnet pioneerHow Does BACnet Work?41

Transport SystemLANsInternetworking

Representing InformationObjects

Making Requestsand InteroperatingServicesApplication LanguageSource: David Fisher, PolarSoftPresentation TitleName & Company of PresenterBACnet works by dividing the problem of interoperability into three distinct areas, and by defining methods and standards for implementing each. All information within an interoperable BACnet device is modeled in terms of one or more information objects. Each object represents some important component of the device, or some collection of information which may be of interest to other BACnet devices. BACnet devices ask each other to perform services. For example, a device to which a temperature sensor is attached, may perform the service of reading the temperature and providing this information to another device which needs it. The model of objects and services is realized by encoding messages into a stream of numeric codes which represent the desired functions or services to be performed. The "language" of this encoding is common to all BACnet devices. BACnet devices actually exchange information and do things by sending and receiving electronic messages containing this coded application language. BACnet provides flexibility by allowing multiple types of transport systems to be used to convey these coded messages between devices. The transport system uses different types of electronic messaging standards and methods to convey coded messages. Even though different transport methods are used, the coded message content remains the same. This philosophy allows the designer or specifier to choose the most cost-effective transport method for a given application. The critical thing to keep in mind is that BACnet allows you to use multiple types of transport mechanisms for electronic messages, but the contents of the messages are the same language. Typical System View42

Management LevelIntegration LevelField Controller LevelOperator WorkstationEthernet or IP LAN

Router

GatewayMSTP LANProprietary LANASCs & AACsApplication LevelProprietary ControllersBACnet-enabled Applications & other apps

Part 2BACnetthe community

Engineers & EducatorsMembers of ASHRAE12 standard regions with 7-16 chapters in eachBeyond America, ASHRAE reaches into Canada and South America.Beyond the Americas, ASHRAE reaches into Hong KongMiddle EastScotlandMalaysia IndiaWalesPhilippines AfricaIrelandSingapore EuropeTaiwan ScandinaviaThailand England44

SSPC 135Consists of 7 working groups:ApplicationsLighting ApplicationsLife Safety & SecurityNetwork SecurityObjects & ServicesUtility IntegrationXML & Web Services

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Manufacturers, Integrators, OwnersBACnet InternationalFormed in January 2000 to "encourage the successful use of the data communication protocol, "BACnet", in building automation and control systems, through interoperability and compliance testing, educational programs, and promotional activities."46

Corporate BI Members47

PlugfestsAmong the many initiatives undertaken by BACnet International are interoperability workshops or plugfests.Dozens of member compnaies routinely take part in these 3-day events for validating product interoperability.48

Presentation TitleName & Company of PresenterNo hype, no politics. No marketing guys like me allowed. Engineers just making sure their products interoperate. 3 days of two hour blocks with other vendors of your choice. 30 or so sample questions to test for and freedom to test anything else. Round off 3 days by building as big a system as possible, see how it discovers the entire network, and put it through its paces. Interests GroupsBIGs consist of users, integrators, manufacturers, contractors, and other interested parties.

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BIG-SUBIG-FIBTLBACnet Testing LaboratoriesEstablished under direction and continued supervision of BACnet International in Feb 2000Our goal is to improve interoperability between BACnet products through a combination of BTL lab testing, multi-vendor interoperability testing, and adherence to the BTL's device implementation guidelines. (Jim Butler, BTL Manager)Lists products by issuing mark50

BTLHas freedom to make requirements above and beyond the minimum requirements specified in the standard.Manufacturers are given pretest guidelines.Requires an extended engineering commitment of manufacturers.51Part 3BACnetand you

BACnet & YouWhy go BACnet?Engineer & owner considerationsIs it really interoperable?Whats next?53

BACnet BenefitsIt is an accepted standard domestically (ASHRAE/ANSI 135-2004), in Europe (CEN TC 247), and worldwide (ISO 16484-5).It was developed specifically for building systems.While HVAC is at its roots, the standard nicely incorporates other integrated functions.

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BACnet BenefitsIt can be implemented on low-cost networks (dedicated or shared) and is extremely flexible in LAN types.BACnet devices are cost-competitive with long-standing proprietary devices.The standard specifically provides for scheduling, trending, and alarming.55

BACnet BenefitsIt is easily scalable at all levels for any size job.It is completely open and not dependent on specific hardware.It provides for automatic device discovery (saving installation costs).56

Presentation TitleName & Company of PresenterBACnet allows intelligent systems from various industries and manufacturers to exchange information, such as temperatures, setpoints, schedules, trend logs and alarms, and coordinate equipment operation to achieve optimum building performance. It saves facility owners/managers the costs of purchasing, engineering and maintaining custom interfaces for supervising packaged HVAC equipment (e.g. chillers), as well as integrating diverse building systems such as HVAC, lighting, fire, elevators, electrical services, etc.

BACnet empowers facility owners/managers with the flexibility of expanding and adding systems without being locked into one manufacturer. Instead, they can select the most appealing technology and services available and gain investment protection because current systems can be expanded without replacing the entire system.

BACnet ChallengesIt does not specify hardware configuration. Therefore, configuration tools (required for initial device setup) vary by manufacturer. No standard application types are defined; therefore, its not yet plug-n-play.

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Presentation TitleName & Company of PresenterBy design that there are no defined config tools. Allows manufacturers to distinguish themselves. An applications working group exists in the SSPC 135. Proposals for macro object types are being examined. ConsiderationsBecome familiar with PICSProtocol Implementation Conformance StatementsDefined formatSpecify device type, BIBBS supported, Object Types supported, and Data Link layer transport options.Required for each BACnet deviceAvailable to you58Presentation TitleName & Company of PresenterA general indication of how the protocol has been implemented in particular devices. A general measure of product capability. This is how different manufacturers can learn what they need to know to ensure interoperability.Refer to page 452 of standard (informative).

ConsiderationsBecome familiar with PICS.Look for native BACnet.Native BACnet typically refers to a device that inherently represents data in BACnet format and communicates utilizing BACnet messaging. Native BACnet devices can be connected to a BACnet system without requiring a gateway device or software driver to translate to and from any proprietary protocols. (Source: Delta Controls website)59ConsiderationsBecome familiar with PICS.Look for native BACnet.Specify BTL listed products.This is the BACnet communitys seal of approval.Note exception for operator workstations (no testing yet provided).60Presentation TitleName & Company of PresenterThis is the BACnet communitys seal of quality.ConsiderationsBecome familiar with PICS.Look for native BACnet.Specify BTL listed products.Need spec writing assistance? Do not go to the standard (at least for this purpose).Use your manufacturers reps.Try www.ctrlspecbuilder.com.61

Presentation TitleName & Company of PresenterRefer to page 452 of standard (informative).ConsiderationsBecome familiar with PICS.Look for native BACnet.Specify BTL listed products.Get spec writing assistance if needed. Use protocol analyzers.62

Presentation TitleName & Company of PresenterThese networks can be complex. When something goes wrong or doesnt work, its difficult to determine where the fault lies. A protocol analyzer can help. Cimetrics, Polarsoft, Frontline. Check out the communications, reveal whats bad. Some even capture and decipher whats on the wire. ConsiderationsBecome familiar with PICS.Look for native BACnet.Specify BTL listed products.Get spec writing assistance if needed. Use protocol analyzers.Demand training.63

Presentation TitleName & Company of PresenterTIs it really Interoperable?64

YES!Presentation TitleName & Company of PresenterNot plug-n-play. To drop in a VAV controller from manufacturer X and a pre-existing network from manufacturer Y, youll need to determine how the others are configured, use manufacturer Xs configuration tool to set up the replacement controller, then drop it in. Other considerations: beware of proprietary objects and properties. Sample Interoperability450 Golden Gate, San FranciscoPhillip Burton Federal BuildingLandmark BACnet installation using two vendor systems (Alerton BACtalk and Trane Tracer Summit) on BACnet network. 9000 points, over 1000 VAV terminal units, 8 large AHUs, 13 single-zone AHUs

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Sample InteroperabilityPaducah Community College, KentuckyBACnet installation using two vendor systems (Alerton and Reliable Controls) on BACnet network. 6 buildings, 1000 points66

Sample InteroperabilityNY Metropolitan Hospital, ManhattanBACnet installation using two vendor systems (Delta Controls and KMC Controls) on BACnet network.Recent isolation wing renovation brought KMC AACs onto the Delta ORCAview network.

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Sample Interoperability/IntegrationUniversity of Arizona435 total buildings. BACnet IP campus WANNumerous vendor systems featuring BMA members Automated Logic Corporation and FieldServer TechnologiesALCs WebCTRL manages the front end. FieldServer integrates numerous devices and systems (including Modbus, LonWorks, and Simplex) into the BACnet network.68

Where is BACnet Going?BACnet support of IP communications lays the necessary groundwork for enterprise-wide challenges.To meet these challenges, however, will require greater utilization of Internet protocols developed in the IT realm.69

XML & Web ServicesNot really applicable to field-level controllers but high-level communications.XML provides for examining high-level data while not being dependent on the communication protocol of the BAS, such as BACnet.So, BACnet manufacturers need to support XML in the operator workstation, for example.Further, web services, such as .NET, provide for greater possibilities in information exchange.The SSPC 135 XML Working Group is defining how data can be exchanged consistently between building automation systems and other enterprise management systems.70Presentation TitleName & Company of PresenterBACnet community also tied into oBIX (OASIS Open Building Information Xchange)Further Resourceswww.bacnet.orgwww.bacnetinternational.org

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So, what are you waiting for?72