Specifications

79
• The CONTROL ALGORITHM STATUS screens (which
include the CAPACITY, OVERRIDE, LL_MAINT,
VFD_HIST, CUR_ALRM, LOADSHED, WSMDEFME,
and OCCDEFCM screens) display information that helps to
diagnose problems with chilled liquid temperature control,
chilled liquid temperature control overrides, hot gas bypass,
surge algorithm status, and time schedule operation. Refer
to Table 14.
• The CONTROL TEST screen under the SERVICE menu
facilitates the proper operation and test of temperature
sensors, pressure transducers, oil reclaim output, head
pressure output, oil pump, liquid pumps, tower control, and
other discrete on/off outputs while the compressor is
stopped. It also has the ability to lock out the compressor
and turn on liquid pumps for pumpout operation. The ICVC
shows the temperatures and pressures required during these
operations.
• From other SERVICE tables, the operator or technician can
access configured items, such as chilled liquid temperature
resets, override set points, etc.
• If an operating fault is detected, an alarm or alert message is
generated and displayed on the ICVC default screen. A
more detailed message — along with a diagnostic message
— is also stored into the ALARM HISTORY and ALERT
HISTORY tables. Refer to Tables 15 and 16.
• Review the ALERT HISTORY table to view other less crit-
ical events and abnormal conditions which may have
occurred. Compare timing of relevant alerts and alarms.
Checking Display Messages — The first area to
check when troubleshooting the 23XRV chiller is the ICVC
display. If the alarm light is flashing, check the primary and
secondary message lines on the ICVC default screen (Fig. 15).
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 and ALERT HISTORY tables on the ICVC
SERVICE menu also contain a message to further expand on
the fault condition. Note that the date format in these tables is
MM/DD/YY. For a complete list of possible alarm messages,
see Table 16. If the alarm light starts to flash while accessing a
menu screen, press the softkey to return to the default
screen to read the alarm message. The STATUS screen can also
be accessed to determine where an alarm exists. A “C” to the
right of a parameters value means there is a communications
fault on that channel.
Checking Temperature Sensors — Except for the
motor temperature sensors, all temperature sensors are installed
in thermowells. This eliminates the need to drain the refriger-
ant, oil, or liquid from the chiller to replace the sensor. All
temperature sensors are thermistor-type sensors. This means
that the resistance of the sensor varies with temperature. All
sensors have the same resistance characteristics.
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 17A or 17B. 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. Table 17A or 17B lists the relationship
between 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 control is powered on.
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. 3 for sensor locations. Temperature sensors are
inserted into a thermowell in the refrigerant or liquid circuits.
When installing a new sensor thermowell, apply a pipe sealant
or thread sealant (RCD part number 56507) to the thermowell
threads. Coat the temperature sensors with thermally conduc-
tive grease (RCD Part Number PP8024) before inserting into
the thermowell.
DUAL MOTOR TEMPERATURE SENSORS — For servic-
ing convenience, there are 2 sensors on the motor temperature
sensor. If one of the sensors is damaged, the other can be used
by simply moving a wire. The number 2 terminal in the sensor
terminal box is the common line. To use the second sensor,
move the wire from the number 1 position to the number
3 position.
Checking Pressure Transducers — There are as
many as 9 pressure transducers on 23XRV chillers. They deter-
mine EVAPORATOR PRESSURE, CONDENSER PRES-
SURE, oil pressure leaving filter, oil sump pressure,
DISCHARGE PRESSURE, and optional CHILLED LIQUID
DELTA P and CONDENSER LIQUID DELTA P. The
EVAPORATOR PRESSURE and CONDENSER PRESSURE
transducers are also used by the PIC III to determine the refrig-
erant temperatures. The OIL PRESSURE DELTA P (oil pres-
sure leaving filter – oil sump pressure) is calculated by the
CCM.
All pressure transducers should be calibrated prior to initial
start-up. 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 (239) is declared. If the transducer
reading is suspected of being faulty, check the TRANSDUCER
VOLTAGE REF supply voltage. It should be 5 vdc ± .5 v
displayed in CONTROL TEST under PRESSURE TRANS-
DUCERS. If the TRANSDUCER VOLTAGE REF. is correct,
the transducer should be recalibrated or replaced.
Also check that inputs on CCM J5-1 through J5-6 have not
been grounded and are not receiving anything other than a 4 to
20 mA signal.
COOLER CONDENSER PRESSURE TRANSDUCER
AND OPTIONAL LIQUIDSIDE FLOW DEVICE CALI-
BRATION — Calibration can be checked by comparing the
pressure readings from the transducer to an accurate refrigera-
tion gage reading. These readings can be viewed or calibrated
from the HEAT_EX screen on the ICVC. The transducer can
be checked and calibrated at 2 pressure points. These calibra-
tion 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 calibration. For
oil pressure delta P, the optional cooler and condenser
liquid delta P, or flow device calibration, leave the trans-
ducer in place.
NOTE: If the cooler or condenser vessels are at 0 psig
(0 kPa) or are open to atmospheric pressure, the transduc-
ers can be calibrated for zero without removing the
transducer from the vessel.
EXIT