AS controllers dropping offline (BACnet Command Priority related).


Following an upgrade to V1.5 from V1.4 the AS goes off/ online.

Product Line

SmartStruxure Solution


Automation Server AS

Enterprise Server ES

V1.50 and above.


Following an upgrade to V1.5 from V1.4 the AS goes off/ online caused by an incorrect setting of the Default Priority Level.


This issue only occurs if the site has changed the BACnet "Default Priority Level" from the default value of 16, to 8 or a smaller numeric value in the Automation Server while running in V1.4.

So before upgrading to 1.5 make sure the "Default Priority Level" within the Automation Server is set to 9 or higher.

If the system has been upgraded with the incorrect values, then: 

  • If the site uses single servers, or the ES/AS communication still operates correctly, then this can be corrected by changing the setting in both the AS and the ES to a value of 9 or higher.
  • If after upgrading a multiserver configuration and the AS does not stay online, then a Hotfix can be used fix the problem using the following steps:

1. Apply the hot fix #; available from Product Support Services

2. Fix the multi-server (by detaching/re-attaching the servers)

3. Correct the two properties (AS and ES).

WARNING: It is essential for any BACnet system at 1.5 or later that the "Default Priority Level" has a larger numeric value than the "Force Priority Level, otherwise some BACnet functions may not behave as expected, this also applies even if the hot fix is installed.

The effects of not setting the Default above the Force Priority level are:

1. If Force Priority Level is equal to the Default Priority Level:

Changing the Value of a BACnet value or a BACnet output object will cause the Value to appear Forced. This applies to the BACnet objects in both SBO servers and those in 3rd party BACnet devices.

2. If Force Priority Level has a larger numeric value than the Default Priority Level:

Changing the Value of objects mentioned above will cause the Priority Override icon overlay to be turned on next to the Value property in the WorkStation’s property grid.

Note: The Default and Force Priority Level are located/ defined in the Green "System" folder, "Interface Manager", "BACnet" for each Server.