BACnet alarms in Home Assistant

Alarms the controller already tracks are shown in Home Assistant. Nothing is configured or acknowledged on the device. Each device gets two entities and fires an event.

Alarm binary sensor

The Alarm binary sensor turns on while any imported object has its IN_ALARM status flag set, or the device reports an active alarm.

Active alarms sensor

Active alarms sensor listing a high-limit alarm

The Active alarms sensor shows the number of active alarms the device reports through the BACnet GetEventInformation service. It is polled with every poll.

Its alarms attribute lists every entry the device reports, including objects that are back to normal but still wait for an acknowledgement at the building management system. Those do not count as active. At most 50 entries are listed, active ones first, with alarms_truncated: true when there are more. Each entry has:

object_type and instance
object_name
event_state: high-limit, low-limit, offnormal, fault and so on
acknowledged: which transitions are acknowledged

Objects you did not import are included too. The state unknown means the device does not support GetEventInformation; the Alarm binary sensor still works from the status flags.

The bacnet_alarm event

The event bacnet_alarm fires when an alarm appears, changes state or clears (event_state: normal). Event data:

Field	Meaning
`device_id`	BACnet device instance
`object_type`	Type of the object in alarm
`instance`	Instance number of the object
`object_name`	Name of the object
`event_state`	New state, for example `high-limit` or `normal`
`previous_event_state`	State before the change

Alarms that are already active when Home Assistant starts do not fire an event.

For a notification automation, see Notify on BACnet alarms.

Note: GetEventInformation does not carry the alarm message text. That only exists in event notifications sent to the notification recipients of the controller, which this integration does not receive.