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