OM AGSB-5
33
Alarms and Events
Situations may arise that 1) require some action from the chiller, or that 2) should be logged
for future reference. A condition that causes a shutdown and requires manual reset is known
as a stop alarm. Other conditions can trigger what is known as an event, which may or may
not require an action in response. All stop alarms and events are logged. The Unit
Controller and the Circuit Controller have different Alarms and Events.
Unit Stop (Shutdown) Alarms
This table identifies each unit stop alarm, gives the condition that causes the alarm to occur,
and states the action taken as a result of the alarm. (See the “Stop Alarms” section under the
Circuit Controller for a description of these alarms.)
The alarm output and red button LED are turned ON when any stop alarm occurs. They are
turned OFF when all alarms have been cleared.
Table 21, Unit Stop Alarms
Description Occurs
When:
Action
Taken
No Evaporator Water Flow
(NOTE)
Evap Pump State = RUN AND Evap Flow Digital Input
= No Flow for time > Flow Proof SP
Rapid Stop
Evaporator Freeze Protect
Evap LWT goes below evap freeze protect setpoint
Rapid Stop
Leaving Evaporator Water
Temperature Sensor Fault
Sensor shorted or open
Rapid Stop
Outside Air Temperature
Sensor Fault
Sensor shorted or open
Normal Shutdown
pLAN Failure
No other controller found on the pLAN for 60 seconds
Rapid Stop
NOTE:
Beginning with this software version, two automatic resets per day (beginning at 12:00 am)
are allowed on the flow loss alarm. The Unit State remains on Auto and the evaporator will go back
to Start, waiting for flow.
Unit Events
The following events only generate a warning message to the operator. Chiller operation is
not affected. They are logged in the Event Log with a time stamp.
Table 22, Unit Events
Description Occurs
When:
Action
Taken
Reset
Entering Evaporator Temperature
Sensor Fault
Sensor is open or
shorted
Cannot use return water
temperature control
Automatic
Circuit Stop (Shutdown) Alarms
The following table identifies each circuit stop alarm, gives the condition that causes the
alarm to occur, and states the action taken because of the alarm. All stop alarms require
manual reset. Rapid stop alarms do not initiate a pumpdown before shutting off. All other
alarms will initiate a pumpdown. The occurrence of a circuit stop alarm only affects the
circuit on which it occurred.
Summary of Contents for AGS 206A
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