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Chiller Troubleshooting
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.
Table 27. Alarm state descriptions
Alarm State
Normal
Compressor Alarm
Compressor Fault
Severity
Controller Warning (within 5%
of controller Fault)
Controller Fault
Alarms
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 does not usually affect
compressor operation but serves as a warning that
compressor operates in nearly 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.
ARTC-SVX014A-EN
Action Taken By Compressor
No Action Required.
Compressor self regulates and reports "At Maximum".
Compressor marked "Fault" and shuts down for reset.
Most faults reset automatically, and the compressor is
return to the "Idle" pool. Only affects the faulted
compressor, chiller can still operate
No Action Required except to react to demand of
controller.
No Action Required except to react to command from
controller.
The controller implements a five-stage alarm management
strategy in order to stay online as long as possible. The
alarm management routine operates as follows:
Action Taken By Controller
No Action Required.
No Action Required. HMI annunciates alarm and logs.
Chiller controller tries to compensate for the missing
compressor with PI-Loop and staging up if other
compressors available. Compressor Fault is annunciated and
logged in the HMI.
Controller reduces demand to alleviate warning condition.
HMI annunciates alarm and logs.
Controller enters Shutdown send 0% demand to all
compressors. HMI annunciates fault and logs. Most controller
faults are reset automatically and when reset complete chiller
and compressor return to "Idle".
If the fault cannot be reset automatically, the chiller
controller places that compressor in the Offline state. The
compressor requires a power cycle to clear and reset the
fault. After clearing, the compressor returns to Idle state.
A maximum of three compressor 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.
If compressor trips out on a fault while the chiller is running
and then recovers to Idle, controller selects it as the last
compressor to start-up when the load increases.
Freeze Protection
The chiller system monitors both Ambient and LCHWT for
potential incidents of freezing. If either threshold is
breached, the chiller is in Freeze Protection mode. The
chiller must be powered on for this function to work.
In Freeze Protection mode, all pumps are enabled at the
maximum speed and all fluid isolation valves are opened. If
pumps or valves are not controlled by the chiller, the
system can still be provided with an hardwired output and a
BMS signal.
Optional Sequences, Power Failure, and
Rapid Restart
If a chiller is equipped with Rapid Restart feature and the
site has sufficient power backup to run the chiller, when
power fails, the controller remembers which compressors
were running when power failed and restarts them when
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