User Manual

Alarm management
Effects of BACnet properties on alarm response
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Alarm enable [EnAlm]
[EnAlm] (Boolean type) is used to enable and disable the monitoring of OFFNORMAL alarms. OFFNORMAL
alarms will only be detected if [EnAlm] is TRUE. This is equivalent to the standard BACnet property
Alarm_Enable.
FAULT alarms are monitored independently of the value of the alarm enable property [EnAlm]. Monitoring
is continuous and cannot be disabled.
If [EnAlm] is changed from TRUE to FALSE during operation, the timer for all deviation monitoring periods
[TiMonDvn] will be reset to zero. As soon as the value of [EnAlm] reverts to TRUE, the associated
[TiMonDvn] timer starts counting to its preset value again from zero.
The value of [EnAlm] can be modified via BACnet clients or using the CFC editor online. During operation, if
[EnAlm] is changed from TRUE to FALSE while an OFFNORMAL alarm is still active, this will result in an
immediate state transition to TO_NORMAL1. In other words, the existing OFFNORMAL alarm condition is
seen as having cleared, and the alarm state of the alarm source is updated accordingly.
Enable event [EnEvt]
[EnEvt] (Boolean type) is used to enable and disable the transfer of OFFNORMAL and FAULT alarms.
OFFNORMAL and FAULT alarms are only transferred if [EnEvt] is TRUE. This is equivalent to the standard
BACnet property Event_Enable.
Enable event detection [EnEvtDet]
[EnEvtDet] (Boolean type) lets you turn the intrinsic/algorithmic reporting on/off. OFFNORMAL and FAULT
alarms are only forwarded when [EnEvtDet] = TRUE. This is equivalent to the standard BACnet property
Event_Detection_Enable.
Event state [EvtSta]
This variable denotes the current alarm state of the object. It can accept three values: NORMAL,
OFFNORMAL (in the case of analog HIGH_LIMIT and LOW_LIMIT values) and FAULT. The value of the
variables is updated immediately after the associated alarm state transition. This is equivalent to the
standard BACnet property Event_State.
Feedback value [FbVal]
[FbVal] is a feedback signal input, configured at a physical input via a separate hardware address. This use
of a physical input can also be the source of reliability errors. [FbVal] can be neither overridden nor
commanded. If [FbVal] is not configured at a physical input, then, by definition, it will be equal in value to
Present Value, in which case no OFFNORMAL alarms can be issued via the output object. This is
equivalent to the standard BACnet property Feedback_Value.
Unlike the binary output and multistate output blocks, the analog output function block does not use
[FbVal] as a criterion for OFFNORMAL alarm conditions. If [FbVal] is used, it can be a source of reliability
errors and can result in FAULT alarms.
Hi limit [HiLm]
This parameter (data type Real) determines the high alarm limit. If [PrVal] exceeds the high limit value
[HiLm] for longer than the period defined under [TiMonDvn], an OFFNORMAL alarm condition prevails,
namely: HIGH_LIMIT.
Enable limit [EnLm]
This variable only exists in the BACnet view of analog blocks (for reasons of compatibility with the BACnet
standard). It has exactly the same meaning as the alarm enable variable [EnAlm] and its current value is
derived from the value of [EnAlm] (that is, [EnLm = EnAlm], Limit enable = Enable alarm). This variable is
equivalent to the standard BACnet property Limit_Enable.
Low limit [LoLm]
This parameter (data type Real) defines the low alarm limit. If [PrVal] exceeds the high limit value [LoLm]
for longer than the period defined under [TiMonDvn], an OFFNORMAL alarm condition prevails, namely:
LOW_LIMIT. This is equivalent to the standard BACnet property Low_Limit.