Specifications

CHECK SENSOR ACCURACY — Place the sensor in a
medium of known temperature and compare that temper-
ature to the measured reading. The thermometer used to
determine the temperature of the medium should be of
laboratory quality with 0.5° F (.25° C) graduations. The sen-
sor in question should be accurate to within 2° F (1.2° C).
See Fig. 7 for sensor locations. The sensors are immersed
directly in the refrigerant or water circuits. The wiring at each
sensor is easily disconnected by unlatching the connector.
These connectors allow only one-way connection to the sen-
sor. 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 each on the bearing and motor
temperature sensors. 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
8 pressure transducers on 19XRT 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 sup-
ply pressure transducer value and the oil transmission sump
pressure transducer value difference is calculated by the CCM.
The CCM module then displays the differential pressure. In
effect, the CCM reads only one input for oil pressure for a
total of 5 pressure inputs: cooler pressure, condenser pres-
sure, oil differential pressure, cooler waterside differential
pressure, and condenser waterside differential pressure. See
the Check Pressure Transducers section (page 70) under Sched-
uled Maintenance.
These 5 pressure transducers can be calibrated if neces-
sary. It is not usually necessary to calibrate at initial start-up.
However, at high altitude locations, it is necessary to cali-
brate the transducers to ensure the proper refrigerant
temperature/pressure relationship. Each transducer is sup-
plied with 5 vdc power from the CCM. If the power supply
fails, a transducer voltage reference alarm occurs. If the trans-
ducer 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.
TRANSDUCER REPLACEMENT — Since the trans-
ducers are mounted on Schrader-type fittings, there is no
need to remove refrigerant from the vessel when replacing
the transducers. Disconnect the transducer wiring by pulling
up on the locking tab while pulling up on the weather-tight
connecting plug from the end of the transducer. Do not pull
on the transducer wires. Unscrew the transducer from the
Schrader fitting. When installing a new transducer, do not
use pipe sealer (which can plug the sensor). Put the plug
connector back on the sensor and snap into place. Check for
refrigerant leaks.
Be sure to use a back-up wrench on the Schrader fitting
whenever removing a transducer, since the Schrader fit-
ting may back out with the transducer, causing a large
leak and possible injury to personnel.
Control Algorithms Checkout Procedure — One
of the tables on the CVC SERVICE menu is CONTROL
ALGORITHM STATUS. The maintenance screens may
be viewed from the CONTROL ALGORITHM STATUS
table to see how a particular control algorithm is operating.
These maintenance screens are very useful in helping to
determine how the control temperature is calculated and guide
vane positioned and for observing the reactions from load
changes, control point overrides, hot gas bypass, surge pre-
vention, etc. The tables are:
CAPACITY Capacity
Control
This table shows all values
used to calculate the chilled
water/brine control point.
OVERRIDE Override
Status
Details of all chilled water con-
trol override values.
HEAT_EX Surge/
HGBP
Status
The surge and hot gas bypass
control algorithm status is
viewed from this screen. All
values dealing with this control
are displayed.
LL_MAINT LEAD/LAG
Status
Indicates LEAD/LAG operation
status.
OCCDEFCM Time
Schedules
Status
The Local and CCN occupied
schedules are displayed here
to help the operator quickly de-
termine whether the schedule
is in the 9occupied9 mode or
not.
WSMDEFME Water
System
Manager
Status
The water system manager is a
CCN module that can turn on
the chiller and change the
chilled water control point. This
screen indicates the status of
this system.
Control Test — The Control Test feature can check all
the thermistor temperature sensors, pressure transducers, pumps
and their associated flow devices, the guide vane actuator,
and other control outputs such as hot gas bypass. The tests
can help to determine whether a switch is defective or a pump
relay is not operating, as well as other useful troubleshoot-
ing issues. During pumpdown operations, the pumps are en-
ergized to prevent freeze-up and the vessel pressures and
temperatures are displayed. The Pumpdown/Lockout fea-
ture prevents compressor start-up when there is no refrig-
erant in the chiller or if the vessels are isolated. The Termi-
nate Lockout feature ends the Pumpdown/Lockout after the
pumpdown procedure is reversed and refrigerant is added.
LEGEND TO TABLES 8A - 8J
CCM — Chiller Control Module
CCN — Carrier Comfort Network
CVC — Chiller Visual Control
CHW — Chilled Water
ISM — Integrated Starter Module
PIC II — Product Integrated Control II
VFD — Variable Frequency Drive
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