Direct Digital Control (DDC) Networks - etouches

1 Direct Digital Control (DDC)NetworksBy Greg JourdanWenatchee Valley CollegeMay 7th, 2014 (1:25-2:20 )Agenda HVAC DDC system architecture Open system interconnection architecture models DDC topologies Open Protocols-BACnet, Lon, Modbus andNiagara/ Tridium Networks Common solutions to upgrade existing HVACDDC systems and how to integrate controls. Advantages and disadvantages of open systemsWhy Use Open DDC Systems?Because Open DDC Systems IntegrateThe DDC Manufacturer s ControlsModern DDC Controls HaveFour Level Architecture-What are they?Courtesy Alerton ControlsFour Level ArchitectureLevel One Sensors Courtesy Alerton ControlsFour Level ArchitectureLevel Two Field Controllers Courtesy Alerton ControlsFour Level ArchitectureLevel 3 Integration & Open Systems Courtesy Alerton ControlsFour Level ArchitectureLevel 4 Management Integration Courtesy Alerton ControlsThus, Modern DDC Controls HaveFour Level ArchitectureCourtesy Alerton ControlsDDC Networks and ArchitectureLAN ConfigurationsCourtesy DDC-Online OrgDDC Networks and ArchitectureLAN ConfigurationsCourtesy DDC-Online OrgDDC Networks and ArchitectureLarge SystemsCourtesy DDC-Online OrgDDC TopologiesDDCNETWORKTOPOLOGIEST here are three basic configurationsused to connect DDC ComputerControls, what are they?

2 DDCNETWORKTOPOLOGIEST here are three basic configurationsused to connect DDC ComputerControls, They are:1. Bus2. Ring3. StarBus topology This type of network was widely used in the 1980 s In this configuration every computer (node) shares thenetworks total bus capacities. In this configuration adding more DDC panels willreduce the access speed on the network . Each computer communicates to other computers on thenetwork independently this is referred to asPEER-TO-PEER networkingProblems with BusTechnology One of the main problems with this type ofnetwork is that it is not very fault tolerant, abreak or defect in the bus would affect thewhole networkRing Topology In Ring topology each node is connected to the twonearest nodes so the entire network forms a circle Data only travels in one direction on a Ring networkHowRing Topologyworks A node has information to send to anothercomputer on the network so it sends theinformation out on the network This method of repeating the data helps keep theintegrity of the data readable by other computersStar topology In a Star topology every node is connectedthrough a central device such as a Hub.

3 Switchor Router Compared to a Ring or Bus topology a Startopology requires that more thought be put intoits setupHUBThe Good and Bad of aStar network The upside of a star network is that if anyone cable fails then only the node connectedon that cable would be affected Another positive point to this type ofnetwork is that it is very simple to join twostar Networks together by connecting theircentral devices to each otherHUBWhat are Some Open Protocols?Open Protocols BACnet Lon Modbus Tridium Not really an Open ProtocolWhat is a Protocol?A protocol is?Protocol Inner WorkingsA protocol is a set of rules defining theformat of data transmission betweentwo or more protocol defines: Data format and composition Addressing Error checking Data compression Send/receive message notificationFor communications to work effectivelybetween two or more devices, the rulescovering the required functionality mustbe interpreted and implementedexactlythe same wayThe OSI Modelexplains the basicsOpen Protocol Forces DDC Manufacturer s todo What?

4 Open Protocol Forces DDC Manufacturer s toIntegrate and Share DataAutomation systems allow communication withmultiple vendors including: HVAC Equipment Fire alarm, security Lighting, fan units PLCs (Programmable Logic Controllers) Boilers and chillersOpen Communication Standards SoftwareIntegration(BACnet, LON, Modbus, Tridium) BACnet, was developed by ASHRAE True, Non-proprietary, Open Protocol Industry Standardized Multiple Vendor ControllersBACnet Software is theDDC Standard ProtocolCourtesy York/Johnson ControlsBACnet Connects Various Manufacturersof DDC ControlsThe Principles of How BACnet Works32 Transport System LANs InternetworkingRepresentingInformation ObjectsMaking Requestsand Interoperating ServicesApplication LanguageSource: David Fisher, PolarSoftTypical BACNet System View33 Management LevelIntegration LevelField Controller LevelOperatorWorkstationEthernet or IP LANR outerGatewayMSTP LANP roprietary LANBACNet PanelsApplication LevelProprietary ControllersBACnet-enabled Applications & other appsBACnet the standardWhat is BACnet?

5 35 What is BACnet? A book An open standard A data communications protocol An acronym:BuildingAutomation andControlNetworks A means of integrating building systems A way of life!36So .. BACnet is a data communications protocoland an agreed-upon set of rules for creatinginteroperable Networks of building .. Building Automation Systems (BAS) HVAC Central Plant (Chillers, Boilers,Large Air Handlers) Lighting Perimeter and Object Security Fire and Life Safety Elevators The integration of all of the Started this BACNet Thing?39 Who Started this BACNet Thing? A working group (standard projectcommittee) of the American Society ofHeating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Began work in 1987 under tremendousopposition (some said it wouldNEVER be done). Published as a standard in 1995.

6 Supported and maintained byASHRAE Standing Standard ProjectCommittee the Standard Defines In essence, the standard defines themessages that devices exchange and howthey are .. The rules of the protocol apply to Electrical signaling Addressing network access (master/slave, peer-to-peer) Error checking Flow Control Message sequencing, segmentation, check pointing Presentation format (compression, encryption) Message format42 Source: Mike Newman, BACnet pioneerBACNet PyramidBIBBSS ervicesDevicesObjectsProperties43 The protocol can be viewed as a matrix of The nucleus to theBACnet atom thesmallest piece ofBACnet information Properties can be readand written. Properties can providecommand Control . They consist of namesand Example: high_limit = The standard requires some properties;other properties are optional; still others canbe proprietary.

7 Required properties must be implementedfor each object type. Optional properties do not have to beimplemented, but if they are, they mustconform to the Objects are the fundamentalbuilding blocks (atoms) ofthe standard. Objects represent data thatoriginates in physicalinputs, physical outputs, orsoftware processes. Each BACnet Objectpossesses a number TypesBinary InputBinary OutputBinary ValueAnalog InputAnalog OutputAnalog ValueMulti-stateInputMulti-stateOutputMu lti-stateValueAveragingPID LoopTrend LogCommandCalendarScheduleLife SafetyZoneLife SafetyPointNotificationClassEventEnrollm entProgramFileGroupDevicePulseConverterA ccumulator47 The standard specifies 25 types of objects:Objects Vendors can implement proprietary objecttypes. When they do so, they use standard datatypes to promote IDs Numerical identifier that combines objecttype and instance number.

8 Object types 0 127 are reserved to identifystandard BACnet objects. Object types 128 1023 are used to identifyproprietary IDs BACnet devices will support any mixture ofobject types up to a limit of 4,194,303instances. Object IDs are typically referred to in thismanner:Analog Input, 550 Objects Summary Objects standardize the organization of datato facilitate the exchange of data betweendifferent vendors There are six device types orprofiles specified by thestandard: 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)ServicesBIBBSS ervicesDevicesObjectsProperties53 Think of BACnetservices as themessages that BACnetdevices send to eachother. Some services read andwrite properties of oneor more objects.

9 Other services sendnotification of alarmsor special events. Still other services readand write BACnet services follow a Client-Servermodel. A BACnet client is a device that requests aservice A BACnet server is a device that performs aservice54 Categories of Services Alarm and Event Routing & event notification File Access Accessing & manipulating files contained in devices Object Access Read and write properties Create and delete objects Manipulate lists of data Remote Device Management Remote monitoring and Control of devices Virtual Terminal Used by a client user to establish a connection to an applicationprogram server in another BACnet Read Property56We wish to read the present value for an analog input called SPACE_TEMP Service= Read Property Object Identifier = (Analog Input, Instance 5) Property Identifier = Present_ValueOperator Workstation(client)MS/TP AAC(server)

10 Service= Read Property Object Identifier = (Analog Input, Instance 5) Property Identifier = Present_Value Value = the target machine can locate the object with this ID and the requested properties, theresult would be:The result indicates that the present value of SPACE_TEMP is : ANSI/ASHRAE Standard 135-2004, page 494 What is BIBBS?ServicesDevicesObjectsProperties57 BIBBSBIBBS is:ServicesDevicesObjectsProperties58 BACnet InteroperabilityBuilding Blocks BIBBS are collections ofservices BIBBS define 5 areas ofinteroperability: Data Sharing Alarm and EventManagement Scheduling Trending Device and NetworkManagementBIBBSE xample of Scheduling & TrendingBIBBSD escriptionB-OWSB-BCB-AACB-ASCB-SAB-SSSCH ED-A SCHED-I-B (internal) SCHED-E-B (external) 59 DescriptionB-OWSB-BCB-AACB-ASCB-SAB-SST- VMT-A (viewing & modifying) T-VMT-I-B T-VMT-E-BT-ATR-A (automated trend retrieval) T-ATR-B BACNet Transport Options BACnet IP BACnet Ethernet (8802-3) Master Slave/Token Passing (MSTP) LonTalk Point-To-Point (PTP)60 Transport ComparisonBACnet IPPopular, fast.