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11
3 - CONTROLS
3.1 - Definitions
3.1.1 - Analogue signal
An analogue signal varies in proportion to the monitored
source. It quantifies values between operating limits.
(Example: A temperature sensor is an analogue device
because its resistance changes in proportion to the
temperature, generating many values.)
3.1.2 - Discrete signal
A discrete signal is a -position representation of the value of
a monitored source. (Example: A switch produces a discrete
signal indicating whether a value is above or below a setpoint
or boundary by generating an on/off, high/low, or open/
closed signal.)
3.2 - General
The 19XRV hermetic centrifugal liquid chiller contains a
microprocessor-based control panel that monitors and
controls all operations of the chiller. 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 the cooling load within the
setpoint 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 variable flow pre-whirl assembly that controls the
refrigeration effect in the cooler by regulating the amount
of refrigerant vapour flow into the compressor. An increase
in guide vane opening increases capacity. A decrease in
guide vane opening decreases capacity. The microprocessor-
based controls protect the chiller by monitoring the digital
and analogue inputs and executing capacity overrides or
safety shutdowns, if required.
3.3 - PIC III system components
The chiller control system is called the PIC III (Product
Integrated Control III). See Table 1. The PIC III controls
the operation of the chiller by monitoring all operating
conditions. The PIC III can diagnose a problem and let the
operator know what the problem is and what to check. It
promptly positions the guide vanes to maintain the 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 bypass valve, if installed. The PIC III controls provide
critical protection for the compressor motor and control
the VFD. The PIC III can interface with the Carrier Comfort
Network (CCN) system if desired. It can communicate
with other PIC I, PIC II, or PIC III equipped chillers and
other CCN devices.
The PIC III consists of three modules housed inside three
major components. The component names and corresponding
control voltages are listed below (also see Table 1):
• control panel
-
all extra low-voltage wiring (4 V or less)
• power panel
-
115 V a.c. control voltage (per job requirement)
-
115 V a.c. power for oil heater and actuators
-
up to 460 V a.c. for oil pump power
• VFD cabinet
-
chiller power wiring (per job requirement)
Table 1 - Major PIC III components and
panel locations
PIC III component
Panel location
International Chiller Visual Controller (ICVC) and Display
Control Panel
Chiller Control Module (CCM)
Control Panel
Control Transformer Circuit Breakers CB1, CB2
Control Panel
Oil Heater Contactor (1C)
Power Panel
Oil Pump Contactor (2C)
Power Panel
Hot Gas Bypass Relay (3C) (Optional)
Power Panel
Control Transformers (T1, T2, T3)
Power Panel
3.3.1 - International Chiller Visual Controller (ICVC)
The ICVC is the “brain” of the PIC III system. This module
contains all the operating software needed to control the
chiller. The ICVC is mounted to the control panel and is
the input centre for all local chiller set points, schedules,
configurable functions, and options. The ICVC has a stop
button, an alarm light, four buttons for logic inputs, and a
backlight display. The backlight will automatically turn off
after 15 minutes of non-use. The functions of the four buttons
or “softkeys” are menu driven and are shown on the display
directly above the softkeys.
The viewing angle of the ICVC can be adjusted for optimum
viewing. Remove the bolts connecting the control panel
to the brackets attached to the cooler. Place them in one of
the holes to pivot the control panel forward to backward
to change the viewing angle. To change the contrast of the
display, access the adjustment on the back of the ICVC.
The ICVC features four factory programmed languages:
•
English (default)
•
Chinese
•
Japanese
•
Korean
NOTE: Pressing any one of the four softkey buttons will
activate the backlight display without implementing a
softkey function.