BACnet – Global standard for open building management solutions

Adopted from:

1. Slides from Christian Mueller, Honeywell Building Solutions Germany

2. http://www.bacnet.org/Tutorial/HMN-Overview

Amarjeet Singh

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The BACnet History

He has a real problem ...

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The BACnet History

He has got a solution ...

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Increasing Demand for Integration

0

2

4

6

8

10

12

14

16

Number (%)

Lighting

Video

AccessFire

Smoke

Energy M

anagement

Other systems

Percentage of construction projects in Germany

that demand integration

1992

1995

1997

2000

I&I Limited

The European Market 2000-2005

Intelligent Controls in Buildings

5

Heterogeneous System Integration

Cost for

integrating

three systems

System A

System B System C

Resulting

system-

functionality

6

1987

1991

1995

1998

2001

2002

2003

2004

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 135-1995 standard. BACnet also becomes ANSI standard

BACnet becomes EN 1805-1 and ENV13321 by CEN TC247

FND withdrawn by CEN as ENV

ANSI/ASHRAE 135-2001 published

BACnet becomes worldwide ISO norm as the only BMS-protocol

The first BACnet devices are conformance tested in Europe

BACnet History ...

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What is BACnet?

BACnet is a communication standard that allows for data exchange (including complex data) between systems from various vendors Correspondingly allows for interoperability of devices and

systems from various vendors

BACnet is most suited for HVAC control applications

Integration with other building sub-systems

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What can BACnet Provide?

BACnet does standardize transactions like: COS/COV (Change of State/ Change of Value)

Alarm/event handling supporting alarm/event priority

Historical data

Data access control

Command priority

File transfer

Save/Restore of programs

Calendar and Scheduling functionality

BACnet is independent from any specific hardware, operating system or software platform

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BACnet Objects

Objects Represent physical inputs, physical outputs and software

processes

Devices and systems are seen as black boxes consisting of a number of objects

BACnet objects only define the outside behaviour of the devices and systems – no internal functionality is defined

Examples A physical device (device objects)

A temperature input (analog input)

A relay control (binary output)

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Object Properties

Standard Objects have required and optional properties defined Properties are of the form “name and value”

Vendors may add proprietary object properties or vendor specific objects to a device

Object_Name ROOM_TEMP

Object_Type ANALOG INPUT

Present_Value 20.3

Unit

High_Limit 30.0

Low_Limit 15.0

required

optional

62 = °C

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BACnet Object Types

BACnet defines 23 object types

For each of the above object, minimum behaviour (properties it contains and services it provides) is also defined

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BACnet Binary Object

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BACnet Object Identifiers

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BACnet Devices

Most important object types in BACnet

Represent controllers

Contain a list of point objects related to the device (e.g. I/O if a device)

Typical BACnet device might have 16 BI and BO objects, 2 or 3 Schedule objects, and so on.

BACnet Device is uniquely located by network number (ranges between 1-65534) and MAC address (ranges between 1-99 for MS/TP)

Device Object Identifiers are unique “internetwork wide” 15

Standard BACnet device profiles

B-OWS BACnet Operator Workstation, GLT

B-BC BACnet Building Controller

B-AAC BACnet Advanced Application Controller

B-ASC BACnet Application Specific Controller

B-SA BACnet Smart Actuator

B-SS BACnet Smart Sensor

B-GW BACnet Gateway

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Proprietary Objects

Proprietary objects: Vendor may create proprietary objects or proprietary properties for standard objects Objects/Properties to be documented in the same style

as standard objects

Must use BACnet-defined data types to represent values

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BACnet Services

Services Communication between BACnet devices and systems is

done using specific services.

Services can be used for example to read object properties.

Server: Object that provides the service

Client: Object that requests a service

Most objects can be both server and client

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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)

A Direct Digital Control (DDC)-system for example may act as

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

S C

Initiate

Service

Execute

Service

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BACnet Services

BACnet currently includes 38 services on the application layer which are subdivided into 5 categories: Object Access

Remote Device Management

Alarm and Event

File Access

Virtual Terminal

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Services - Object Access

Object access services include services like: Read and write data (object

properties) Request a specific data range (e.

g. to retrieve trend log data) Services to create other objects at

runtime or delete them (like notification class objects or schedule objects)

Services to add data to lists or remove data from lists (data point and events to/from notification class objects)

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Services - Device Management

Network start-up Who-Is, I-Am

Who-Has, I-Have

Time Synchronization

Request device start-up (via network) …

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Services - Alarm- and Event

Services include Alarm- and event handling and

COV/COS (Change of Value/State)

Request alarm summary list (e. g. after a communication restart)

Services to acknowledge alarms

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Alarm and Event handling

BACnet allows for three different methods for alarm and event handling COV Events

One or more recipients subscribe specific changes to state or value from a COV-server using SubscribeCOV(Property) service.

The COV-Server sends changes to the receivers that have subscribed for the event using (Un)ConfirmedCOVNotification

Intrinsic Event Reporting

The recipient list of alarms and events from specific objects will statically or dynamically be managed using NotificationClass objects

The objects to support intrinsic alarming will have to support various optional properties like the EventEnable property

Algorithmic Change Events

In order to support algorithmic change events, the EventEnrollment object needs to be supported. The EventEnrollment object list contains stages and values of datapoints that need to be monitored.

In case of a limit violation, the distribution of alarms/events can either be handled by the EventEnrollment object itself (if recipients are defined) or via a Notification Class object list if a NC object is defined with the object in alarm.0

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BACnet Confirmed Services

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BACnet Unconfirmed Services

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BACnet Networking Options

Ethernet

BACnet over IP

Serial (RS232/RS485)

ARCnet

MS (Master Slave)/TP (Token Passing)

LonTalk (is not equal to LonMark!)

Data-Link

Media-Access

Physical

Network

Application BACnet Application Layer

BACnet Network Layer (allows Routing)

ISO 8802-2 Type 1

RS 485 RS 232

MS/TP PTP LonTalk

ARCNET ISO 8802-3 „Ethernet“

BACnet/IP

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Native BACnet

To interconnect multiple LANs a “network layer”

protocol is required

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Routers for Interconnection

Routers implement the BACnet network layer protocol and

allow devices on disparate networks to communicate 29

Routers for Interconnection

• Routers build and maintain routing tables automatically using

network layer protocol messages (e.g. Who-Is-Router-To-

Network, I-am-Router-To-Network)

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Gateways for Translation

Gateways translate messages before retransmission – can

get tricky if the two protocols do not support same messaging

concepts 31

Example Gateway: Modbus to BACnet

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BACnet Data on IP Network - I

• Annex H: Place in the standard where the process of converting

BACnet packet into IP packet is defined

• Annex H routers talk to each other using UDP (encapsulating BACnet

packet)

• Each message shows up twice in each network 33

BACnet Data on IP Network - II

• BACnet/IP: BACnet + Intrinsic IP

• BACnet/IP devices: don’t need Annex H routers to talk

• IP routers don’t normally broadcast messages: Hence the need for

BBMD (BACnet Broadcast Management Device)

• Alternatively IP multicast may be used 34

BACnet Broadcast Management Device

The BACnet Broadcast Management Device (BBMD) handles broadcast telegrams (Who-Is, Who-Has, I-Am, I-Have, …) through routers that connect different IP-subnets.

The BBMD can be an external device or be integrated in another BACnet device like B-BC, B-OWS.

BBMD: act as Annex-H devices except that they only handle forwarding of broadcasted (infrequent) IP messages

BBMD Function

IP-Segment A IP-Segment B

IP-Router

B-BC

B-OWS B-OWS

B-BC

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Foreign Devices Within BACnet

Foreign devices can talk to any BACnet device directly but will only receive broadcast if registration procedure is followed

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BACnet/IP Devices

BACnet/IP devices should behave like other BACnet devices in terms of their network activities. They should be able to Communicate directly with peer devices on their network Make use of local broadcasts, received by all peer devices on their

network Send remote broadcasts to devices residing on networks with different

network number Global broadcasting should still work as before

Assumptions: Devices have unique address (IP address) and they know what the

address is Device do not know (or do not need to know) their BACnet network

number

BACnet/IP uses UDP for IP communication

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The BACnet PICS

PICS: Protocol Implementation Conformance Statement

The PICS is a standard way of describing the BACnet functionality of a specific solution in a kind of table format and contains information about BACnet services supported

BACnet standard objects supported including information Whether or not BACnet objects can be created and deleted

during runtime

Which object properties are supported and which are read-only

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The BACnet PICS

PICS continued ... Data Link Layer Options

Description of the network options supported (like Ethernet, BACnet /IP)

Special functionality Restrictions to properties, if exist

e. g. the max. number of characters for a key name or the character set (e. g. ANSI X3.4)

The BACnet PICS is an important means for end customers and consultants to understand the functionality provided by a BACnet solution.

This is achieved through BACnet Interoperability Building Blocks (BIBBs) Standard device profiles

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BACnet Interoperability Building Blocks

BIBBs – Define a set of BACnet services to provide a specific function. BIBBs are either client (A) or server (B) related.

There are BIBBs for the following areas of interoperability: Data Sharing (DS)

Alarm and Event Notification (AE)

Scheduling (SCHED)

Trending (T)

Device Management (DM)

Network Management (NM)

Virtual Terminal Management (VT)

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BACnet Interoperability Building Blocks

BIBBs example: DS-COVP-B (Data Sharing-COVP-B)

(A) is user (Client), (B) is server (Server)

(A) subscribes change of value of a specific property from (B)

(B) serves (A) with COV of the object property without the need of polling

BACnet Service Initiate Execute

SubscribeCOVProperty X

ConfirmedCOVNotification X

UnconfirmedCOVNotification X

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Standard BACnet Building Blocks

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BIBBS, tested in Europe today

DS-RP-B (B) provides data upon request from (A)

DS-WP-B (B) allows a value to be changed by (A)

DS-COV-B (B) accepts subscription requests from (A) and replies with COVNotifications

DM-DDB-B (B) provides information about itself to (A)

DM-DOB-B (B) provides information about its objects upon request from (A)

DM-DCC-B (B) responds to comm. control request from (A)

DM-TS-B / DM-UTC-B (UTC – Greenwich Mean Time) (B) accepts time sync. request from (A)

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BACnet PICS (Extract)

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B-BC Example: Honeywell Excel Web

LINUX operating system

10/100MBit/s network interface

Integrated Web-Server with HTML-pages installed for parameter setting, local operation via browser

No need for ActiveX controls

Trend capacity can be expanded using standard CF memory cards

Up to 1.000 BACnet objects

I/O modules based on LonTalk (78kbps, Free topology wiring

DIN rail or direct mounting

LINU

X

inside

!

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Case Study: Technology compound at the German Parliamentary Buildings

Reichstag

Jakob-KaiserHaus

Paul-Löbe

Haus

Supervisorx BMS

Marie-Elisabeth-Lüders

Haus

BACnet/IP

Supervisory BMS of the Energy compound

Ethernet (TCP/IP)

Unter den Linden 71

Wilhelmstraße 60

Unter den Linden 50

Honeywell

Schadowstr. 12/13

und Dorotheenstr. 88

Dorotheenstraße 88

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Case Study: Technology compound at the German Parliamentary Buildings

Access to BACnet objects like schedule, calendar and loop

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BACnet/OPC comparison

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OPC Introduction

The task: Get data from a PLC (Programmable logic controller) into

a Microsoft based application within a PC-based network. Prior to OPC a special driver needed to be written and

maintained for each protocol that had to be integrated into a visualisation (SCADA system)

Target: Provide a standard interface with standard objects (OPC server)

that every PLC-vendor could integrate and that could also be integrated by every vendor of visualisations (OPC client)

Provide a standard interface between plant control level and information technology

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OPC History

1995 A task force composed of Fisher-Rosemount, Rockwell Software, Opto 22,

Intellution, and Intuitive Technology developed a basic, workable, OPC specification.

OPC = Object linking and embedding for process control

1996 A simplified, stage-one solution was released in August 1996.

OPC foundation group started up.

1998 OPC becomes an industry standard

1998 OPC Data Access 2.0 published

2001 Compliance Testing and Certification program available

2004 The OPC Foundation has got more than 300 members.

Honeywell is also a member of the OPC Foundation.

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OPC Introduction

OPC (OLE for Process Control) is a Client-/Server Software Interface, based on the Microsoft COM / DCOM component technology. It is used to exchange data between different applications on one machine (COM) or between different applications on a network (DCOM).

OPC is not a new bus standard, no norm It may be compared with a printer driver available with a

printer which is the interface between the hardware and the office application

OPC is best suited for Simple I/O type of information which need to be

integrated into office applications Data exchange between software applications

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OPC data types, object model

OPC only supports simple data objects (so called OPC Items). OPC Items consist of Value, state

Time stamp

Information about the quality of data

OPC Object model OPC Groups are defined on an OPC server. OPC groups

contain OPC Items that are handled in a similar way. E. g.: Periodical data transmission

Data transmission on a COV/COS

Each OPC Item may have properties defined like value range, engineering unit

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OPC Specifications

OPC Data Access Used to move real-time data from PLCs and other control

devices to HMIs and other display clients. Standard on the market is OPC DA 2.04. The Data Access 3 specification is now a Release Candidate.

OPC Alarms & Events Provides alarm and event notifications on demand

(in contrast to the continuous data flow of Data Access). OPC Clients can subscribe for alarms and events from the

OPC server (OPC-AE 1.10).

OPC Data eXchange This specification takes OPC from client/server to server-to-server with communication across Ethernet

field bus networks.

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OPC Specifications

OPC Historical Data Access Where OPC Data Access provides access to real-time,

continually changing data, OPC Historical Data Access provides access to data already stored. (OPC DX 1.0)

OPC Security OPC Security specifies how to control client access to these servers in order to protect this sensitive

information and to guard against unauthorized modification of process parameters (OPC Security 1.0)

OPC XML-DA OPC XML-DA is developed to expose plant floor data

using XML and SOAP. Specification still under development

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Need more information?

OPC Foundation web pages www.opcfoundation.org

OPC European membebr web pages www.opceurope.org

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BACnet

Vendor independence ISO Standard, independent

from OS, hardware or vendor

Best suited for Automation and

management level

Peer-to-Peer communication for HVAC control and safety controls

Communication IP support, Client-Server

OPC

Vendor independence De-facto-Industry Standard,

based on Microsoft COM/DCOM technology

Best suited for Move real-time data from PLC

to visualisation and business applications

Peer-to-Peer communication possible if OPC data eXchange extension becomes available

Communication IP support, Client-Server

OPC/BACnet Comparison

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BACnet

Specifications/Profiles

Data Sharing (with

priority)

Alarms and Events

Historical Trends

Scheduling

Device and Network

Management

Access Control

mechanisms build in

BACnet via XML:

Specification in public

review

OPC

Specifications/Profiles

Data Access (DA)

Alarm & Events (AE)

Historical Trends: Only few

implementations exist, Normally

done on SCADA level

Scheduling: needs to be done

on SCADA level

Access Control: available. Only

a few Implementations make

use of OPC Security

OPC XML-DA : spec. under

development

OPC/BACnet Comparison

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BACnet

Planning and Start-up

BACnet is not Plug & Play : example due to optional object properties

An in depth comparison of the PICS is required

Test installation recommended

OPC

Planning and Start-up

OPC allows for Plug & Play if the network is correctly set up.

No optional object properties

Configuration of DCOM in complex network environment can be tricky.

Many times firewalls do not allow for port 15 (OPC/DCOM) to be open as several virus attacks (like W32Lovsan) came through this port

OPC/BACnet Comparison

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BACnet and OPC complement each other

BACnet is most suitable if it comes to ... Building Management applications (alarming with

acknowledgement, scheduling, save and restore of application programs, command priority, Peer-to-Peer data communication)

Data exchange between devices (e. g. an energy manage-ment application requires data from various DDC systems on the LAN for peak load control)

OPC is best suited if it comes to ... Simple data exchange between a SCADA system and a

PLC or integration of a fire panels into a Visualisation

Data exchange with IT- or ERP (Business) applications

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