How can I change the Device Instance ID of a VT7000 series BACnet thermostat?

Issue

Using the keypad on the stat to set the comm address may result in duplicate Device Instance IDs on a BACnet network.

Product Line

Andover Continuum, SmartStruxure Solution

Environment

Viconics

Cause

Find New BACnet Device does not result in new Viconics stat added to the system. This is due to the default assignment ID scheme used by Viconics. It is resulting in a duplicate Device ID on the BACnet network.

Resolution

By default, the Device Instance ID (called the Device Node ID in Continuum) is generated using the first two digits of the model of the thermostat + the comm (MAC) address assigned to the stat. Example: For a VT7200C5000 thermostats with MAC address 115, the default Device Instance would be 72115.

The problem is that when installing the same model stats on multiple MSTP networks on the same BACnet system, this scheme can easily result in duplicate Device Instance IDs.  

The resolution is to change the duplicates or use a scheme to assign unique IDs manually to all the stats on a system.  Any number between 1 and 4194303 (between 1 and 3FFFFF in Hex) is accepted by the thermostat.

One scheme would be to use the BACnet Network ID and append the MAC address to it. Since each BACnet Network ID must be unique across the entire system, and the MAC address on each BACnet Network must be unique, this assures the combination is unique across the system. 

For example, if you have a bCX with an MSTP bus on comm2 that has a BACnet Network ID - Comm2 of 2765 and a stat with a MAC address of 9, assign it the Device Instance ID 2765009.    

A BACnet Explorer that provides write access to the Device Instance ID is required to change the default Device Instance ID. See Lessons Learned #14525 for a link to the Viconics VT7000 BACnet Configurator utility . 

For additional support on the above utility contact Viconics Support at  1-800-563-5660.