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• If an operating fault is detected, an alarm message is
generated and displayed on the CVC default screen. A
more detailed message — along with a diagnostic mes-
sage — is also stored into the ALARM HISTORY table.
Checking Display Messages —
check when troubleshooting the 23XL chiller is the CVC dis-
play. If the alarm light is flashing, check the primary and sec-
ondary message lines on the CVC default screen (Fig. 17).
These messages will indicate where the fault is occurring.
These messages contain the alarm message with a specified
code. This code or state appears with each alarm and alert mes-
sage. The ALARM HISTORY table on the CVC SERVICE
menu also contains an alarm message to further expand on the
alarm. For a complete list of possible alarm messages, see Ta-
ble 9. If the alarm light starts to flash while accessing a menu
screen, press the
softkey to return to the default screen
EXIT
to read the alarm message. The STATUS screen can also be ac-
cessed to determine where an alarm exists.
Checking Temperature Sensors —
ture sensors are thermistor-type sensors. This means that the re-
sistance of the sensor varies with temperature. All sensors have
the same resistance characteristics. If the controls are on, deter-
mine sensor temperature by measuring voltage drop; if the con-
trols are powered off, determine sensor temperature by measur-
ing resistance. Compare the readings to the values listed in
Table 10A or 10B.
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 temperature are listed in
Table 10A or 10B. 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 con-
trol is energized. Table 10A or 10B lists the relationship be-
tween temperature and sensor voltage drop (volts dc measured
across the energized sensor). Exercise care when measuring
voltage to prevent damage to the sensor leads, connector plugs,
and modules. Sensors should also be checked at the sensor
plugs. Check the sensor wire at the sensor for 5 vdc if the con-
trol is powered on.
Relieve all refrigerant pressure or drain the water before
replacing the temperature sensors.
CHECK SENSOR ACCURACY — Place the sensor in a
medium of known temperature and compare that temperature
to the measured reading. The thermometer used to determine
the temperature of the medium should be of laboratory quality
with 0.5º F (.25º C) graduations. The sensor in question should
be accurate to within 2º F (1.2º C).
See Fig. 11 and 12 for sensor locations. The sensors are im-
mersed directly in the refrigerant or water circuits. The wiring
at each sensor is easily disconnected by unlatching the connec-
tor. These connectors allow only one-way connection to the
sensor. When installing a new sensor, apply a pipe sealant or
thread sealant to the sensor threads.
DUAL TEMPERATURE SENSORS — For servicing con-
venience, there are 2 sensors on the motor temperature sensor.
If one of the sensors is damaged, the other can be used by sim-
ply moving a wire. The number 2 terminal in the sensor termi-
nal box is the common line. To use the second sensor, move the
wire from the number 1 position to the number 3 position.
The first area to
All
tempera-
77
Checking Pressure Transducers —
pressure transducers on 23XL chillers. They determine cooler,
condenser, oil pressure, and cooler and condenser flow. The
cooler and condenser transducers are also used by the PIC II to
determine the refrigerant temperatures. The oil pressure valve
(oil pressure transducer — evap pressure transducer) is calcu-
lated by the CCM.
All pressure transducers should be calibrated prior to initial
start-up. However, at high altitude locations, it is necessary to
calibrate the transducers to ensure the proper refrigerant
temperature/pressure relationship. Each transducer is supplied
with 5 vdc power from the CCM. If the power supply fails, a
transducer voltage reference alarm occurs. If the transducer
reading is suspected of being faulty, check the supply voltage.
It should be 5 vdc ± .5 v displayed in CONTROL TEST under
CCM Pressure Transducers. If the supply voltage is correct, the
transducer should be recalibrated or replaced.
COOLER CONDENSER PRESSURE TRANSDUCER
AND WATERSIDE FLOW DEVICE CALIBRATION —
Calibration can be checked by comparing the pressure read-
ings from the transducer to an accurate refrigeration gage read-
ing. These readings can be viewed or calibrated from the
HEAT_EX screen on the CVC. The transducer can be checked
and calibrated at 2 pressure points. These calibration points
are 0 psig (0 kPa) and between 25 and 250 psig (173 and
1724 kPa). To calibrate these transducers:
1. Shut down the compressor, cooler, and condenser
pumps.
NOTE: There should be no flow through the heat
exchangers.
2. Disconnect the transducer in question from its
Schrader fitting for cooler or condenser transducer cal-
ibration. For oil pressure or flow device calibration
keep transducer in place.
NOTE: If the cooler or condenser vessels are at
0 psig (0 kPa) or are open to atmospheric pressure, the
transducers can be calibrated for zero without remov-
ing the transducer from the vessel.
3. Access the HEAT_EX screen and view the particular
transducer reading (the EVAPORATOR PRESSURE or
CONDENSER
PRESSURE
HEAT_EX screen). To calibrate oil pressure or water-
side flow device, view the particular reading
(CHILLED WATER DELTA P and CONDENSER
WATER DELTA P on the HEAT_EX screen, and OIL
PUMP DELTA P on the COMPRESS screen). It
should read 0 psi (0 kPa). If the reading is not 0 psi
(0 kPa), but within ± 5 psi (35 kPa), the value may be
set to zero by pressing the
appropriate transducer parameter is highlighted on the
CVC screen. Then press the
value will now go to zero. No high end calibration is
necessary for OIL PUMP DELTA P or flow devices.
If the transducer value is not within the calibration
range, the transducer returns to the original reading. If
the pressure is within the allowed range (noted above),
check the voltage ratio of the transducer. To obtain the
voltage ratio, divide the voltage (dc) input from the
transducer by the supply voltage signal (displayed in
CONTROL TEST menu in the CCM PRESSURE
TRANSDUCERS screen) or measure across the posi-
tive (+ red) and negative (– black) leads of the trans-
ducer. For example, the condenser transducer voltage
input is measured at CCM terminals J2-4 and J2-5.
The voltage ratio must be between 0.80 and 0.11 for
the software to allow calibration. Pressurize the trans-
ducer until the ratio is within range. Then attempt cali-
bration again.
There are 8
parameter
on
the
softkey while the
SELECT
softkey. The
ENTER
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