Operation
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IOM 1281-2 • CENTRIFUGAL WATER CHILLERS
Table 19: Critical Alarms
Screen Text
Occurs When
Action Taken
Troubleshooting
Clear
Evaporator Pressure
Low
Evaporator Press < Low Suction Pressure-Stop SP for
60 sec. Delay reduces linearly to 10 sec at 10 psi below
SP, then drops to 0 below 10 psi below SP
Rapid Stop
Causes: Low or No Evaporator Water Flow. Low
refrigerant level in evaporator. Incorrect setpoint
value for leaving water temperature.
Manual
Discharge Pressure
High
Discharge pressure > High Condenser Pressure SP
Rapid Stop
Causes: Low or No Condenser Water Flow
Manual
Compressor Starting -
Vanes/Interlock Open
Compressor state = PRELUBE for 30 sec after Prelube
timer expires
Rapid Stop
Manual
Low Oil Delta Pressure
(Comp State=PRELUBE, RUN, UNLOAD, or
POSTLUBE) & Net Oil Press < Low Net Oil Press SP
Rapid Stop
Manual
Low Oil Feed
Temperature
(Comp State=RUN or UNLOAD) & Oil Feed temp <
(Evap Saturated Ref. Temp + Low Oil Delta Temp SP)
for > 1 min
Rapid Stop
Manual
High Oil Feed
Temperature
Temp > High Oil Feed Temperature SP
Rapid Stop
Manual
Low Motor Current
%RLA > Motor Current Threshold SP with Compressor
ON for 30 sec
Rapid Stop
Manual
Discharge Temperature
High
Temp > High Discharge Temp - Load SP
Rapid Stop
Causes: Low or No Condenser Water Flow
Manual
Mechanical High
Pressure
Digital Input = High Pressure
Rapid Stop
Manual
Motor Stator
Temperature High
Digital Input = High Temperature
Rapid Stop
Rotor and/or stator cooling circuit fault
Causes: Motor stator cooling solenoid not open,
rotor cooling stepper motor not functioning
correctly, motor rotor superheat or gain setpoints
incorrect (contact factory)
Manual
Surge Temp High
/ Surge Detected -
Running
Surge Temp > Surge Temp SP
Rapid Stop
Surge Temperature = the suction temperature
minus the leaving chilled water temperature.
Manual
Surge Temp Slope
High / Surge Detected
- Starting
Surge Temp Slope > Surge High Slope SP
Rapid Stop/No Start
Manual
No Starter Transition
Starter Transition Digital Input = No Transition AND
Compressor ON for > 15 seconds
Rapid Stop/No Start
Manual
No Compressor Stop
%RLA > Motor Current Threshold SP with Compressor
OFF for 30 sec
Unit asked to stop but
current still detected
Auto
Starter Fault
Starter Fault Digital Input = Fault AND Compressor
State = START, PRELUBE, RUN, or UNLOAD
Rapid Stop
Manual
Low Oil Pressure Start
Compressor State = START for 30 sec
Rapid Stop/No Start
Manual
Evaporator Water Flow
Loss
Evaporator Flow DI = No Flow for > Evap Flow Loss
Delay SP
OR
(No Flow
AND
shutdown due to low
evaporator pressure
OR
bearing fault) with compressor
running. (Alarm is masked during power fail — timer
restarts after power returns)
Rapid Stop
Causes: Loss of evaporator flow, evaporator
pump off, evaporator head gasket leaking or
missing, sensor wiring fault, evaporator flow
sensor failure
Manual
Condenser Water Flow
Loss
Condenser Flow DI = No Flow for > Cond Flow Loss
Delay SP
OR
(No Flow
AND
shutdown due to high
Cond pressure
OR
bearing fault) with compressor
running. (Alarm is masked during power fail — timer
restarts after power returns)
Rapid Stop
Causes: Loss of condenser flow, condenser
pump off, condenser head gasket leaking or
missing, sensor wiring fault, condenser flow
sensor failure
Manual
Leaving Evaporator
Water Temperature
Sensor Fault
Sensor shorted or open
Rapid Stop
Chilled Water Flow Switch Open
Manual
Evaporator Pressure
Sensor Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Condenser Pressure
Sensor Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Suction Temp Sensor
Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Discharge Temp
Sensor Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Oil Feed Temp Sensor
Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Oil Sump Temp Sensor
Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Oil Feed Pressure
Sensor Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Oil Sump Pressure
Sensor Fault
Sensor shorted or open
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Evaporator Pump #1
Fault
No flow indicated for (5 sec) with Evaporator Pump
#1 ON AND [the other pump is available (per the
evaporator Pump SP) AND has not faulted]
Rapid Stop/No Start
Check for loose wires or failed sensor
Manual
Evaporator Pump #2
Fault
No flow indicated for (5 sec) with Evaporator Pump
#2 ON AND [the other pump is available (per the
evaporator Pump SP) AND has not faulted]
Rapid Stop/No Start
Evaporator flow not detected. Causes: improper
pump wiring
Manual
