The BACnet object alarm states InAlarm, Unacked and Unreset are grouped in the following blocks:
- The CommonAlarm block for Desigo PX
- The CommonEvent block for Desigo room automation
The difference between CommonAlarm and CommonEvent is, that the CommonAlarm block supports intrinsic reporting. The alarm detection and notification of the CommonEvent block is handled by a special Event Enrollment object called CommonEventEnrollment. The CommonEventEnrollment block also handles the common alarm reset / ack and common manual intervention functions.
All alarms generated by alarm-generating BACnet objects on the same chart level or subordinate charts are automatically grouped into a common alarm. There is therefore no need for the user to create a common alarm by establishing links or interconnections. The engineering process simply involves placing the block at the required chart level. No other configuration steps are necessary.
Common alarm reset / ack
Similarly, all the alarms covered by this block can be the subject of a common alarm reset and acknowledge.
Acknowledging the common alarm object is equivalent to acknowledging all objects on the same and lower levels in the hierarchy.
Resetting the common alarm object is the equivalent to resetting all objects on the same and lower levels in the hierarchy.
Common manual intervention
The same common alarm object also uses the status flag Overridden to indicate the manual operation of one or more of the BACnet objects (with [StatFlag] override facilities) on the same or a lower chart level. Manual intervention are determined on the properties: Out of service [OoServ], overridden, commanding to Prio 7 (manual switch) and Prio 8 (operator).
This diagram shows the practical application of the common alarm object within the technical hierarchy. The common alarm object in the partial-plant compound encompasses all the alarms of this partial plant. The higher-level common alarm encompasses the alarms of both partial plants.