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TROUBLESHOOTING GUIDE
Overview
The PIC6 control system has many features to help the operator
and technician troubleshoot a 19XR chiller.
•
The HMI shows the chiller's actual operating conditions
and can be viewed while the unit is running.
•
The HMI default screen indicates when an alarm occurs.
Once all alarms have been cleared (by correcting the prob-
lems), the HMI default screen indicates normal operation.
For information about displaying and resetting alarms and
a list of alert codes, see the 19XR with PIC6 Controls Op-
eration and Troubleshooting manual.
•
The Configuration menu screens display information that
helps to diagnose problems with chilled water temperature
control, chilled water temperature control overrides, hot gas
bypass, surge algorithm status, and time schedule operation.
•
The quick test feature facilitates the proper operation and
test of temperature sensors, pressure transducers, the guide
vane actuator, diffuser actuator (if equipped), oil pump,
water pumps, tower control, and other on/off outputs while
the compressor is stopped. It also has the ability to lock off
the compressor and turn on water pumps for pumpout op-
eration. The HMI shows the temperatures and pressures re-
quired during these operations.
•
If an operating fault is detected, an alarm indicator is dis-
played on the HMI default screen. A more detailed mes-
sage — along with a diagnostic message — is also stored
in the controller Current Alarms table.
•
Review the Alarms History table to view other less critical
events which may have occurred. Compare timing of rele-
vant events and alarms.
For detailed information about alarms, see the 19XR with PIC6
Controls Operation and Troubleshooting manual. Press the bell
icon in the top right corner of the home screen to access current
alarms and alarm history, and to reset alarms.
Checking Display Messages
The first area to check when troubleshooting the 19XR is the HMI
display. Status messages are displayed at the bottom of the screen,
and the alarm icon indicates a fault. For a complete list of alarms,
see the 19XR with PIC6 Controls Operation and Troubleshooting
manual.
Checking Temperature Sensors
All temperature sensors are thermistor-type sensors. This means
that the resistance of the sensor varies with temperature. All sen-
sors have the same resistance characteristics. If the controls are on,
determine sensor temperature by measuring voltage drop; if the
controls are powered off, determine sensor temperature by mea-
suring resistance. Compare the readings to the values listed in Ta-
bles 13 and 14. The water temperature sensors can be calibrated to
a value of
2.0°F (1.2°C).
RESISTANCE CHECK
Turn off the control power and, from the module, disconnect the
terminal plug of the sensor in question. With a digital ohmmeter,
measure sensor resistance between receptacles as designated by
the wiring diagram. The resistance and corresponding tempera-
ture are listed in Tables 13 and 14. Check the resistance of both
wires to ground. This resistance should be infinite.
VOLTAGE DROP
The voltage drop across any energized sensor can be measured
with a digital voltmeter while the control is energized. Tables 13
and 14 list the relationship between temperature and sensor volt-
age drop (volts dc measured across the energized sensor). Exer-
cise care when measuring voltage to prevent damage to the sen-
sor leads, connector plugs, and modules. Sensors should also be
checked at the sensor plugs.
Relieve all refrigerant pressure or drain the water before
removing any thermowell threaded into the refrigerant
pressure boundary. Failure to do so could result in personal
injury and equipment damage.
51
CAUTION
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