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General —
The 19XR hermetic centrifugal liquid chiller
contains a microprocessor-based control center that monitors
and controls all operations of the chiller (see Fig. 9). The
microprocessor control system matches the cooling capacity of
the chiller to the cooling load while providing state-of-the-art
chiller protection. The system controls cooling load within the
set point plus the deadband by sensing the leaving chilled water
or brine temperature and regulating the inlet guide vane via a
mechanically linked actuator motor. The guide vane is a vari-
able flow pre-whirl assembly that controls the refrigeration ef-
fect in the cooler by regulating the amount of refrigerant vapor
flow into the compressor. An increase in guide vane opening
increases capacity. A decrease in guide vane opening decreases
capacity. The microprocessor-based control center protects the
chiller by monitoring the digital and analog inputs and execut-
ing capacity overrides or safety shutdowns, if required.
PIC II System Components —
The chiller control
system is called the PIC II (Product Integrated Control II). See
Table 1. The PIC II controls the operation of the chiller by
monitoring all operating conditions. The PIC II can diagnose a
problem and let the operator know what the problem is and
what to check. It promptly positions the guide vanes to main-
tain leaving chilled water temperature. It can interface with
auxiliary equipment such as pumps and cooling tower fans to
turn them on when required. It continually checks all safeties to
prevent any unsafe operating condition. It also regulates the oil
heater while the compressor is off and regulates the hot gas by-
pass valve, if installed. The PIC II controls provide critical pro-
tection for the compressor motor and controls the motor starter.
SPEED
VOLTS
AMPS
Hz
Kw
TORQUE
Password
RUNNING
REMOTE
JOG
AUTO
FORWARD
REVERSE
PROGRAM
PRO-
GRAM
Forward
Reverse
ENTER
RUN
JOB
AUTO
MAN
SPEED
VOLTS
AMPS
Hz
Kw
TORQUE
Password
RUNNING
REMOTE
JOG
AUTO
FORWARD
REVERSE
PROGRAM
PROGRAM
Forward
Reverse
ENTER
RUN
JOB
AUTO
MAN
MANUAL RESET
OPTIONAL
METER
PACKAGE
SPEED
VOLTS
AMPS
Hz
Kw
TORQUE
Password
RUNNING
REMOTE
JOG
AUTO
FORWARD
REVERSE
PROGRAM
PROGRAM
Forward
Reverse
ENTER
RUN
JOB
AUTO
MAN
DANGER
HIGH VOLTAGE
+
-
INITIAL DC BUS
MEASUREMENT
POINT
DC BUS BAR
MEASUREMENT
POINT
+
-
VFD
MODULE
COOLING LINES
COMPRESSOR
MOTOR
DISCONNECT
TXV
CONTROL
AND OIL
HEATER
DISCONNECT
OIL PUMP
DISCONNECT
INTEGRATED
STARTER
MODULE
(ISM)
LINE
LOAD
Fig. 7 — Variable Frequency Drive (VFD)
Fig. 8 — Variable Frequency Drive (VFD) Starter Internal View