User Manual

Alarm management
Effects of BACnet properties on alarm response
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blocks (including the BACnet Device Info Object) are only monitored in the operational status RUN.
Corresponds to the standard BACnet Property Out_of_Service.
Present value [PrVal]
OFFNORMAL alarms are monitored exclusively on the basis of the current value of [PrVal] the present
value variable. The source of this present value (whether a process value, operator value, replacement
value or commanded value) is irrelevant. This is equivalent to the standard BACnet property Present_Value.
Reliability [Rlb]
The value under [PrVal] is only plausible if [Rlb] = NO_FAULT_DETECTED.
When [Rlb] <> NO_FAULT_DETECTED, this is precisely the condition for a FAULT alarm.
The BACnet Device Info Object is an exception. The value of [Rlb] for the BACnet device object is
NO_FAULT_DETECTED, except in the case of the fault FLASH_FULL (FAULT condition). This is equivalent
to the standard BACnet property Reliability.
Reference value [RefVal]
[RefVal] is a set point, used to set the value which [PrVal] (the measured value) must assume in order to
initiate an alarm after the time defined by [TiMonDvn] has expired. [RefVal] is equivalent to the standard
BACnet property Alarm_Value.
Reference values [RefVals]
The variable [RefVals] comprises a list of multistate elements. The value range (number of states) of the
items in the list is the same as for [PrVal]. All states to be treated as OFFNORMAL are entered under
[RefVals]. [RefVals] is equivalent to the standard BACnet property Alarm_Values.
Example of [RefVals] : STEP 1, STEP 2, STEP 4
Name Value
State 1 STEP 1
State 2 STEP 2
State 3 STEP 4
In this example, an incoming OFFNORMAL alarm will be detected if [PrVal] = STEP 1, STEP 2 or STEP 4
after expiry of the period defined by [TiMonDvn].
State flag [StaFlg]
The variable [StaFlg] includes the two bits 'In_Alarm' and 'Fault'.
By definition, In_Alarm is TRUE whenever [EvtSta] is not equal to NORMAL.
By definition, FAULT is TRUE whenever [EvtSta = FAULT].
The value of these two [StaFlg] variables is thus derived from another variable.
For each change of the variable [StaFlg] a Change of Value (COV) notification is sent to all COV
subscribers of the alarm-generating object. In this way, the COV subscribers can be kept informed of an
alarm state in their COV server. This is equivalent to the standard BACnet property Status_Flags.
Suppress event detection [SupEvtDet]
[SupEvtDet] (Boolean type) lets you turn the OFFNORMAL and FAULT alarm detection on/off.
OFFNORMAL and FAULT alarms are only detected when [SupEvtDet] = FALSE. This is equivalent to the
standard BACnet property Event_Algorithm_Inhibit.
Event time stamp [TiStmEvt]
This variable (ARRAY [3], type TimeStamp), contains time stamps for the last changes of state of the
alarm-generating object TO_OFFNORMAL, TO_FAULT and TO_NORMAL. The value of the variables is
updated immediately after the associated alarm state transition. This is equivalent to the standard BACnet
property Event_Time_Stamps.
Notification function selector [NotifSel]
This variable specifies if the alarm function is executed as per default pattern (Simple-/Basic-/Extended
alarm) or as per a customized alarm function.