Basic Protocol Information; Bacnet Networks - Daikin MicroTech II Installation And Maintenance Manual

BACnet Networks

Compatibility
The MicroTech II Chiller Unit Controller conforms to the
BACnet Standard (ANSI/ASHARE 135-2004) as stated in the
Protocol Implementation and Conformance Statement (PICS).
See BACnet Protocol Implementation Conformance Statement
on page 102.
BACnet Objects
MicroTech II Chiller Unit Controllers incorporate standard
BACnet object types (i.e., object types defined in the BACnet
Standard) and additional proprietary BACnet object types that
conform to the BACnet Standard. and some include additional
proprietary properties. Objects contain properties that control
unit variables or data points. Some object types occur more
than once in the unit controller; each occurrence or instance has
different property values and controls different unit variables or
data points. Each instance is designated with a unique instance
index. Some properties can be adjusted (read/write properties,
e.g., setpoints) from the network and others can only be
interrogated (read-only properties, e.g., status information).
Each data point accessible from a BACnet network is
described with a table that gives the Object Identifier, Property
Identifier, Full BACnet Reference or path, and the Name
enumeration of the property.
Example of BACnet Data Point
Object Identifier
Type
Object Type
Enumeration
Analog Input 0
Object Name
EntCondWaterTemp
Object Identifier
Object Identifiers are each designated with an Object type as
defined in the BACnet specification. The first column of the
data point definition gives the object type. This object happens
to be the Entering Condenser Water Temperature.
The object identifier is a property of the object that you
can read from the object code. The name of the property
is "Object_Identifier" and the property identifier is 75. The
ASHRAE BACnet specification reserves the first 128 numbers
for ASHRAE defined objects. Manufactures may define
additional object types and assign a number above 127 as long
as they conform to the requirements of the ASHRAE BACnet
specification.
ED 15062-7 • MICROTECH II CHILLER CONTROLLER
Property Identifier
Property Property
Instance
Name Enumeration
18 Present Value
Each object in a chiller controller has a unique identifier.
BACnet object identifiers are two-part numbers of BACnet
Object Identifier data type. The first part identifies the object
type (the first 10 bits of the 32-bit BACnet Object Identifier
[See ANSI/ASHRAE 135-2004 BACnet A Data Communication
Protocol for Building Automation and Control Networks]). The
first column of the data point definition gives the object type.
The second part identifies the instances of that particular object
type (the last 22 bits of the 32-bit BACnet Object Identifier).
The object identifier is shown in the data points listing as two
numbers. The first number is shown in the Type Enumeration
column and designates the Object type enumeration.
The second number is shown in the Instance column and
designates the instance of that particular object type.
Each object also has a name. Object names are character
strings. The object name is a property of the object that you
can read from the object. The name of the property is "Object_
Name" and the property identifier is 77.
Objects are sometimes referred to as an object type and
instance number as they are in the BACnet specification. The
example object above is Analog Intput, Instance 18.
Property Identifier
Each object has a number of properties or attributes. Each
property has a unique identifier of BACnet Property Identifier
data type. Property identifiers are an enumerated set; a
number identifies each member. The value of the Property
Identifier enumeration is shown in the Property Enumeration
85
column. In the example above the property identifier is 85.
Property Name
Each property also has a unique name. Property names are
character strings and shown in the Property Name column.
In the example above the property name is Present Value
(Property Enumeration 85).
Object Name
This property is a character string that is the unique name of
the object in the BACnet device. In the example above the
object name is EntCondWaterTemp
Property Values
Some properties are standard data types and some are
enumerated sets. If the property value is an enumerated set,
all enumerated values and corresponding meaning are given in
the Property Values column of the data point listing.
8
b P I
asIC roToCol nformaTIon
b P
asIC roToCol
www.DaikinApplied.com
I
nformaTIon