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Fail detect
Network fail detect is used to detect when a network input has not been updated
from the network for a period. When the network input has not been updated after
about 5 minutes, the network input will return to a default value, typically 'Invalid'.
The Fail detect is enabled when configured for the network variable and the net-
work input is bound using a network tool. For the Global thermostat controller, the
Fail detect for each network input is enabled based on the information given in this
chapter.
Some network inputs are desired to have the Fail detect enabled when they are not
bound using a network tool. This is useful for sharing sensor data across multiple
controllers using the Global thermostat gateway which allows the control to fall
back to a predetermined action when the network input has not been updated after
a period (e.g., communication is lost). A configuration flag called FDWhenNot-
Bound allows the network input to provide fail detection when it is not bound. For
the Global thermostat controller, FDWhenNotBound for each network input is
enabled based on the table below.
Fail Detect Enable: This is the time until the IRM controller is notified of a failure
on this point.
True: If the parameter has not received an update from the IRM network source in
the Fail detect time, then an alarm is generated, and the Present Value is set to
Invalid.
Fail Detect Fallback Value Select: The value that should be set to 'Out' (when fail-
ure is detected), if the Fail Detect 'Enable' is True and the Fail Detect 'Fallback
Value' is set to "Fixed Value". The Fail Detect only works if "In" is NULL and Fail.
Detect 'Enable' is set to true.
'Update Rate' - Update interval in seconds within which 'Present Value' should get
written over BACnet periodically. 'Present Value' not written within this interval will
result in failure and 'Out' will be set with the value as configured in 'Fallback Value'.
Fallback Value:
•
•
•
•
Fail Detect Delay: Fail detect time depends on the update rate configured.
False: False means the object retains the last value that was written to it until an
IRM network source changes it or the IRM controller has a power outage or reset
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"InvalidValue" - 'Out' is set as NULL,
"LastknownGoodValue" - If the last 'Out' value was not NULL then 'Out' is
retained as it is, otherwise, the value from the 'Default Value' parameter goes to
Out.
"FixedValue" - "Fail Detect Fixed Value" value goes to 'Out'. 'Enable' - Set it to true
to enable the Fail detection feature.
Note - This feature enables monitoring of periodic updates of a function block
over the network.
Fail detect
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