Transcript Hello

BACnet Basics
Ben H. Dorsey III
VP, Marketing & Communications
KMC Controls, Inc.
Preview
• BACnet—the standard (for the techie types)
• BACnet—the community (for everyone)
• BACnet—and you (hey, for you)
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Caution
• BACnet is BIG
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Part 1
BACnet—the standard
What is BACnet?
• An open standard
• A data communications protocol
• An acronym: Building Automation and Control
Networks
• A means of automating buildings and
integrating building systems
• A 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.
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Encompassing . . .
• Mechanical systems
• HVAC Central Plant (Chillers, Boilers, Large Air
Handlers)
• Lighting
• Perimeter and Object Security
• Fire and Life Safety
• Elevators
• The integration of all of the above.
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Who did it?
• A working group (standard project
committee) of the American Society of
Heating, Refrigerating and AirConditioning 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.
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It’s Alive!!!
• By design, the standard is under
continual revision.
• First published in 1995.
• In recent times, most manufacturers’
products have been designed to the
2008 edition of standard.
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Not a Reactive Process
• Addenda 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.)
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What the Standard Defines
• In essence, the standard defines the messages
that devices exchange and how they are
delivered.
message
transport
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Further . . .
• The rules of the protocol apply to
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Electrical signaling
Addressing
Network access (master/slave, peer-to-peer)
Error checking
Flow control
Message sequencing, segmentation, checkpointing
Presentation format (compression, encryption)
Message format
Source: Mike Newman, BACnet pioneer
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Pyramid Scheme
• The protocol can be viewed as a matrix of layers.
BIBBS
Services
Devices
Objects
Properties
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Properties
• The nucleus to the
BACnet atom—the
smallest piece of BACnet
information
• Properties can be read
and written.
• Properties can provide
command control.
• They consist of names
and values.
BIBBS
Services
Devices
Objects
Properties
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Properties
• Example: high_limit = 78.0
• The 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.
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Property Identifiers
• Property 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.
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Objects
• Objects 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.
BIBBS
Services
Devices
Objects
Properties
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Object Types
• The standard specifies many types of objects:
Binary Input
Binary Output
Binary Value
Analog Input
Analog Output
Analog Value
Multi-state
Input
Multi-state
Output
Multi-state
Value
Averaging
PID Loop
Trend Log
Command
Calendar
Schedule
Life Safety
Zone
Life Safety
Point
Notification
Class
Event
Enrollment
Program
File
Group
Device
Pulse
Converter
Accumulator
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Objects
• Vendors can implement proprietary object
types.
• When they do so, they use standard data
types to promote interoperability.
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Object IDs
• Numerical 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.
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Object IDs
• BACnet 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, 5
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Objects—Summary
• Objects standardize the organization of data
to facilitate the exchange of data between
different vendors’ products.
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Devices
• There are several device types or
profiles specified by the
standard:
– Advanced Operator Workstation
(B-AWS)
– Operator Workstation (B-OWS)
– Operator Displays (B-OD)
– Building Controller (B-BC)
– Advanced Application Controller
(B-AAC)
– Application Specific Controller
(B-ASC)
– Smart Actuator (B-SA)
– Smart Sensor (B-SS)
– Other BACnet devices (B-Oth)
BIBBS
Services
Devices
Objects
Properties
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Services
• Think 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.
BIBBS
Services
Devices
Objects
Properties
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Services
• BACnet services follow a Client-Server model.
– A BACnet client is a device that requests a service
– A BACnet server is a device that performs a
service
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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 application
program server in another BACnet device.
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Services—ReadProperty
We wish to read the present value for an analog input called “SPACE_TEMP”
Service= ReadProperty
‘ObjectIdentifier’ = (Analog Input, Instance 5)
‘PropertyIdentifier’ = Present_Value
Operator Workstation
(client)
MS/TP AAC
(server)
Assuming the target machine can locate the object with this ID and the requested properties, the
result would be:
Service= ReadProperty
‘ObjectIdentifier’ = (Analog Input, Instance 5)
‘PropertyIdentifier’ = Present_Value
‘Value’ = 72.3
The result indicates that the present value of “SPACE_TEMP” is 72.3
Source: ANSI/ASHRAE Standard 135-2004, page 494
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BIBBS
• BACnet Interoperability
Building Blocks
• BIBBS are collections of
services
• BIBBS define 5 areas of
interoperability:
– Data Sharing
– Alarm and Event
Management
– Scheduling
– Trending
– Device and Network
Management
BIBBS
Services
Devices
Objects
Properties
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BIBBs Summary Example: B-BC
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Data Sharing
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Alarm & Event Management
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Ability to schedule output actions, both in the local device and in other devices, both binary and analog,
based on date and time
Trending
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Generation of alarm/event notifications and the ability to direct them to recipients
Maintain a list of unacknowledged alarms/events
Notifying other recipients that the acknowledgement has been received
Adjustment of alarm/event parameters
Scheduling
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Ability to provide the values of any of its BACnet objects
Ability to retrieve the values of BACnet objects from other devices
Ability to allow modification of some or all of its BACnet objects by another device
Ability to modify some BACnet objects in other devices
Collection and delivery of (time, value) pairs
Device & Network Management
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Ability to respond to queries about its status
Ability to respond to requests for information about any of its objects
Ability to respond to communication control messages
Ability to synchronize its internal clock upon request
Ability to perform re-initialization upon request
Ability to upload its configuration and allow it to be subsequently restored
Ability to command half-routers to establish and terminate connections
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Transport Options
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BACnet IP
BACnet Ethernet (8802-3)
Master Slave/Token Passing (MSTP)
ARCnet
LonTalk
Point-To-Point (PTP)
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Transport Comparison
BACnet IP
Popular, fast. No real
performance difference
between this and 8802-3.
Use BBMD or PAD router to
get across an IP router.
Broadcast issues.
BACnet 8802-3
Popular, fast. No real
performance difference
between this and IP.
Cannot get across IP
routers.
MSTP
Very popular, especially as a
low-level bus technology for
AACs and ASCs. Uses EIA485 signaling over twisted
pair wiring.
Lower performance.
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BACnet Layers vs OSI Layers
Standard OSI Reference Model
Application
BACnet Layers
Presentation
Session
Transport
Network
BACnet Application Layer
Application
BACnet Network Layer
Network
ISO8802-2 (IEE 8802.3)
Type 1
ISO8802-3
(IEE 802.3)
Equivalent OSI Layer
MS/TP
Data Link
PTP
LonTalk
ARCNET
EIA-485
EIA-232
Physical
Data Link
Physical
Source: ANSI/ASHRAE Standard 135-2004, page 9
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Auxiliary Devices
• Routers
– Useful when networks using different BACnet
transport options need to exchange data.*
Operator Workstation on
BACnet IP network
Router

BACnet MSTP Controller Network
*This concept is referred to as
“Internetworking.”
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Auxiliary Devices
• Gateways
– Useful when devices on a BACnet network
must exchange data with devices on a nonBACnet network.*
Gateway

*This is also
Internetworking.
BACnet network
Proprietary Network
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So, what’s the difference?
• A router is really a pass-through device. It
doesn’t change the form or content of the
message but just the packaging—much 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.
Source: Mike Newman, BACnet pioneer
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How Does BACnet Work?
•Objects
Application Language
Representing
Information
Making Requests
and Interoperating
•Services
Transport System
•LANs
•Internetworking
Source: David Fisher, PolarSoft
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Typical System View
Operator
Workstation
Management Level
Ethernet or IP LAN
Router
Gateway
Integration Level
MSTP LAN
Proprietary LAN
Field Controller Level
ASCs & AACs
Proprietary Controllers
Application Level
BACnet-enabled Applications & other apps
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Part 2
BACnet—the community
Engineers & Educators
• Members of ASHRAE
– 12 standard regions with 7-16 chapters in each
– Beyond America, ASHRAE reaches into Canada and
South America.
– Beyond the Americas, ASHRAE reaches into
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Hong Kong
Malaysia
Philippines
Singapore
Taiwan
Thailand
Middle East
India
Africa
Europe
Scandinavia
England
Scotland
Wales
Ireland
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SSPC 135
• Consists of working groups:
– Applications
– Lighting Applications
– Life Safety & Security
– Network Security
– Objects & Services
– Utility Integration
– XML & Web Services
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Manufacturers, Integrators, Owners
• BACnet International
– Formed 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."
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Corporate BI Members (partial)
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Plugfests
• Among the many initiatives undertaken by
BACnet International are interoperability
workshops or “plugfests.”
• Dozens of member companies routinely take part
in these 3-day events for validating product
interoperability.
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Interests Groups
• BIGs consist of users, integrators,
manufacturers, contractors, and other
interested parties.
BIG-SU
BIG-FI
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BTL
• BACnet Testing Laboratories
– Established under direction and
continued supervision of BACnet
International in Feb 2000
– “Our 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.” (former
BTL Manager)
– Lists products by issuing mark
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BTL
• Has 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.
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Part 3
BACnet—and you
BACnet & You
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Why go BACnet?
Engineer & owner considerations
Is it really interoperable?
What’s next?
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BACnet Benefits
• It is an accepted standard domestically
(ASHRAE/ANSI 135-2008), 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 Benefits
• It 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.
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BACnet Benefits
• It 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).
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BACnet Challenges
• It does not specify hardware configuration.
Therefore, configuration tools (required for
initial device setup) vary by manufacturer.
• No standard application types are defined;
therefore, it’s not yet plug-n-play.
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Considerations
• Become familiar with PICS
– Protocol Implementation Conformance
Statements
– Defined format
– Specify device type, BIBBS supported, Object
Types supported, and Data Link layer transport
options.
– Required for each BACnet device
– Available to you
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Considerations
• Become familiar with PICS.
• Look for “native” BACnet.
– Native BACnet refers to a device that inherently
represents data in BACnet format and
communicates utilizing BACnet messaging. Native
BACnet devices were designed from the ground up
as BACnet (as opposed to adding BACnet
functionality to a previously designed product).
BACnet
“Native” BACnet
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Considerations
• Become familiar with PICS.
• Look for “native” BACnet.
• Specify BTL listed products.
– This is the BACnet community’s seal of
approval.
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Considerations
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Become familiar with PICS.
Look for “native” BACnet.
Specify BTL listed products.
Demand training.
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Is it really Interoperable?
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Interoperability Case Studies
• We’re populating our web site and the web site of
BACnet International with numerous case studies
that illustrate multi-vendor interoperability and
systems integration:
– http://www.kmccontrols.com/products/projectshome.aspx
– http://www.bacnetinternational.net/success/stories.php
• One such KMC project was awarded
“Best in Show” by BACnet International as the
top interoperable project published on the
BI web site in 2010:
– Kuwait Oil Company Project
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Where is BACnet Going?
• BACnet support of IP communications lays
the necessary groundwork for enterprisewide challenges.
• To meet these challenges, however, will
require greater utilization of Internet
protocols developed in the IT realm.
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XML & Web Services
• Not really applicable to field-level controllers but highlevel 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.
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Further Resources
• www.bacnet.org
• www.bacnetinternational.org
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So, what are you waiting for?
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