The BACnet history He has a real problem...

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2 The BACnet history He has a real problem...

3 The BACnet history He has got a solution...

4 BACnet history Foundation of the ASHRAE (American Society of Heating Refrigeration and Air-Conditioning Engineering) committee SPC135. Team charter: Development of a communication protocol which would be neutral and allow monitoring, control and energy management within buildings. First draft version of the new protocol available BACnet was published as ASHRAE standard. BACnet also becomes ANSI standard BACnet becomes EN and ENV13321 by CEN TC247 FND withdrawn by CEN as ENV ANSI/ASHRAE published BACnet becomes worldwide ISO norm as the only BMSprotocol The first BACnet devices are conformance tested in Europe

5 What is BACnet? BACnet (Building Automation and Control Network) is a true, non-proprietary open protocol communication standard. BACnet makes ist possible for products, created by various manufacturers to fully interoperate in a building automated control system The BACnet protocol defines a model for BAS to communicate between devices and systems. The protocol model specifically defines: Data and control functions structured in an object oriented manner Services that describe data requests and responses Network data link types A scalable and flexible internetwork and network architecture

6 Device Integration Physical interconnection Network routing Data representation Data exchange Action-Requests/Response Capability Boiler Chiller Air Handler

7 Functional Integration Data representation options Data exchange options Action-Requests/Response options Capability options HVAC Access Control

8 Application Integration Data representation options Data exchange options BAS Asset Management

9 Application Integration Data representation options Data exchange options BAS Remote Monitoring

10 Tip! Think of network types as different transportation methods for the same message, like delivering a letter via plane, train, or automobile. What networks does BACnet specify? BACnet specifies six network types to accomodate different project and system requirement. - Ethernet - 10Mbs to 10Gbs, CSMA/CD, allows devices to transmit when the medium is clear. - Arcnet - 150kbs to 7.5Mbs, token bus standard, rarely used. - MS/TP (a twisted pair RS-485 network created by BACnet) - 9.6kbs to 76.8kbs, low cost - Point-to-Point (also created by BACnet) - 9.6kbs to 56.0kbs, internet-worked communications over modem, direct cable communication - LonTalk - BACnet/IP (also called BACnet over IP, this was added later to accomodate BACnet messages to be transported across the Internet) - devices only speak BACnet, communicate diretly from device to device.

11 Network Layers

12 BACnet Client/Server architecture A BACnet device may trigger a service or can react on a service request: - Client: Requests services (Service user) - Server: Offers services (Service provider) Initiate Service C S Execute Service A DDC-system for example may act as a - client for various field devices in an automation system, - server for other DDC-systems or for a BMS (Building Management System) that requests specific data or alarms

13 Tip! Objects and Properties are similar in concept to folders and documents in a PC. Think of an object as a folder containing documents describing the information in the folder. The folder is the object, and the documents describing the folder are the properties. BACnet Protocol The BACnet Protocol is based on devices, objects, properties, and services - Devices microprocessor-based unit designed to understand the BACnet protocol, typically a controller, gateway, or user interface that contains a collection of information about the device called objects and properties. (Includes device identifier and instance number) - There are six device types specified by the standard, also known as PICS (Protocol Implementation and Conformance Statement. - PICS disclose the following areas of information about a BACnet device: B-OWS (BACnet Operator Workstation) B-BC (BACnet Building Controller) B-AAC (BACnet Advanced Application Controller) B-ASC (BACnet Application Specific Controller) B-SS (BACnet Smart Sensor) B-SA (BACnet Smart Actuator)

14 - Objects a collection of information within a device, represents physical and virtual information such as AI/AO, DI/DO, algorithms, specifand calculations. ic applications, Standard defines 25 standard object types for which a vendor may be able to provide interoperateability, non standard objects may also be created. Objects will always be identified with object identifiers that are 32- bit binary number containing object type and instance number. Every object has a collection of properties that define the object.

15 - Properties property conveys information about a object, typical object has an extensive collection of properties based on function and purpose of the object. Each propertie contains two pieces of information a name/identifier and values. Its purpose is to allow other BACnet devices to read information about the object and possibly command it to a different value. Properties may be required or optional. The BACnet standard identifies 192 property identifiers.

16 Tip! Services act like the action verb in the BACnet protocol. Services ask for an action to take place, like a read temperature request or a write to setpoint request. - Services are actions that a BACnet device takes to read or write to another BACnet device.currently there are 38 services on the application layer which are subdivided into the following catagories: - Object Access read/write data, create/delete - Device Management discover, time, snchronize, backup, and restore - Alarm and Event alarms and changes of state - File Transfer trend data, program transfer - Virtual Terminal HMI via prompts and menus - Security - Summary