Installation & Operation Manual - Model AVR6000
Contents of this Manual are Subject to Change Without Notification
Page 48
SECTION 7 - BACnet
BACnet® is a standard data communication protocol designed specifically for building
automation and control networks. The AVR controller uses the BACnet MS/TP (Master-
Slave/Token Passing) protocol which is a type of MAC layer implemented using the EIA-485
signaling standard. The performance of the MS/TP network is heavily influenced by the
network traffic load, the assignment of MS/TP node addresses, Baud Rate, and the
configuration of network parameters such as
Nmax_info_frames
and
max_master
.
Additionally, it is imperative the physical network layer is properly configured (cabling, EOL
terminations, bias, etc...) and is verified to be reliable otherwise the network performance can
be compromised.
7.1
BACnet Objects
The AVR AccuValve supports a collection of BACnet-visible objects. In addition to a Device
object whose instance is programmed by writing to the current Object_Identifier or the
“wildcard” Object_Identifier whose instance is 4194303, the AVR supports several standard
object types as described herein. The following table defines the visible objects. The PV
column indicates whether the Present_Value is Read Only “R”, Writable “W” or a
Commanded “C” point.
The standard objects; DEV, AI, AV, AO, BI, BV, and MSI support required properties for those
object types. Object_Name is writable with provision for 64-character maximum length
names. BI Inactive_Text and Active_Text, and MSV State_Text are writable.
Each AI/AV/AO object’s Units property automatically changes to the appropriate unit for US
or SI measurement based on the value of MSV2 and MSV3. Internally Present_Values are
stored in US units and converted to/from SI units only when read or written.
Standard object property values other than Present_Value shall be derived as follows:
Object_Identifier: generated automatically from request
Object_Type: generated automatically from request
Object_Name: writable
Polarity: always NORMAL
Units: MSI3 and MSI4 (Reference BACnet Tables below)
State_Text, Inactive_Text: Active_Text writable
Status_Flags: always {FALSE,FALSE,FALSE,FALSE}
Event_State: always NORMAL
Out_Of_Service: always FALSE
The internal Airflow Control loop dictates the Airflow Actuator Position (AO1) at a priority of
10 and the AccuValve Insight Configuration Software commands the Airflow Actuator
Position at priority 9. Devices external to the AVR that need to control the actuator directly
shall use higher priority levels (8, 7, 6….).
Objects; AI, AV, and AO shall support the COV_INCREMENT property which shall also be
writable.
