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ARTC-SVX007A-EN
Chiller Troubleshooting
Abnormal Operation Sequence
Chiller in Alarm Avoidance
The Chiller Management System continuously monitors for
abnormal system conditions such as low suction pressure,
high discharge pressure, low leaving temperature, high
amp draw and others.
The controller implements a three-stage alarm
management strategy in order to stay online as long as
possible. The alarm management routine operates as
follows:
Figure 46. Chiller alarm management routine chart
Table 20. Alarm state descriptions
Alarm State Action Taken by Controller
All monitored values are normal No action required. Alarm can be deleted from list.
One or more monitored value(s) is within 5% of the alarm setting If system is loading, the system stops loading.
One or more monitored values is equal to or greater than the alarm
setting
System demand is reduced by 0.5% per second until demand reaches 10% or
compressors ride to the surge speed. If the alarm is still present and the compressors are
at the surge speed, the controller will enter ’Stage-out’ state turning compressors off every
2 minutes until the last compressor is left operational.
One or more monitored value(s) is equal to or greater than the trip
setting
Chiller is turned off and all compressors are shutdown. The Fault will be automatically
reset after the time value is setup in the advanced setting screen (default = 3 minutes).
Once the fault has been reset, the system is set back to ‘Idle’ state.
Alarms
The compressor itself monitors its own internal sensors
and employs the same strategy: In Alarm, the compressor
reduces its own power to try to keep from hitting Fault limit.
Hitting the fault limit shuts down the compressor.
Most compressor faults automatically reset at which time
the compressor returns to the 'Idle' state and is ready to
start again.
Arbitration for the chiller as a whole is such that alarms and
faults should occur first at the compressor level then as a
next level, the controller.
All the alarms can be grouped into two main categories:
1. Chiller alarms
2. Compressor alarms
Chiller alarms group comprises chiller control system
alarms, for instance sensors faults or equipment
communication faults and chiller control devices alarms
(other than compressors), for instance flow switches,
pumps, condenser fans etc.
Compressor alarms can be non-critical or critical (fault).
Compressor non-critical alarm conditions cause the
compressor to automatically reduce power so as to avoid
fault conditions. Compressor faults, however, always stop
compressor from operation and require fault condition to
clear before compressor can restart.
Some of the compressor faults are lockout faults. They
require a hard reset – power cycle – before compressor
can restart.
Compressor Faults
If the fault is resettable such as a suction pressure, bearing
displacement or motor over temperature fault, compressor
stops and its state changes to ‘Fault’. The chiller controller
attempts to automatically reset the fault and make the
compressor available again. When compressor comes
back to available its state changes to “Idle”.
If the fault cannot be reset automatically the compressor
state is set to 'Offline' and the compressor will need a hard
reset (Power-Cycle) to reset the fault. After successful
power-cycle, the compressor should return to state 'Idle'
and be ready to start again.
A maximum of three compressor identical faults per hour
are tolerated. If more than three faults in an hour are
generated the compressor is placed in ‘Offline’ state, the
compressor is considered locked out and requires a power-
cycle.
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