Controls; Definitions; General; Pic 5 System Components - Carrier AquaEdge 19XR Start-Up, Operation And Maintenance Instructions Manual

CONTROLS

Definitions

ANALOG SIGNAL
An analog signal varies in proportion to the monitored source. It
quantifies values between operating limits. (Example: A tem-
perature sensor is an analog device because its resistance chang-
es in proportion to the temperature, generating many values.)
DISCRETE SIGNAL
A discrete signal is a 2-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 set point or bound-
ary by generating an on/off, high/low, or open/closed signal.)

General

The 19XR centrifugal liquid chiller contains a microprocessor-
based control center 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 provid-
ing 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 variable flow pre-whirl assembly that con-
trols the refrigeration effect in the cooler by regulating the
amount of refrigerant vapor flow into the compressor. An in-
crease 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 digi-
tal and analog inputs and executing capacity overrides or safety
shutdowns, if required.

PIC 5 System Components

The chiller control system is called the PIC 5 (Product Integrated
Control 5). See Table 1. As with previous PIC versions, the PIC
5 system controls the operation of the chiller by monitoring all
operating conditions. The PIC 5 control system 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 leav-
ing 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 5 controls provide critical protection for the
compressor motor and control the motor starter.
Table 1 — Major PIC 5 Components and
Panel Locations
PIC 5 COMPONENT
Chiller Human Machine Interface (HMI) and
Display
Integrated Starter Module (ISM)
Chiller IO Boards
Oil Heater Contactor (1C)
Oil Pump Contactor (2C)
Hot Gas Bypass Relays (HCLR, HOPR)
(Optional)
Control Transformers (T1, T2, T3)
Temperature Sensors
Pressure Transducers
NOTE: For detailed information about the PIC 5 HMI (human
machine interface), see the 19XR with PIC 5 Controls Opera-
tion and Troubleshooting manual.

Local Start/Stop Control

Local start-up (or manual start-up) is initiated by pressing the
gray Start/Stop icon on the HMI interface. See Fig. 6.
This initiates the PIC 5 starting sequence by displaying the list of
operating modes. Press Local On to initiate start-up. See Fig. 7.
NOTE: Prior to start-up, the start-to-start timer and the stop-to-
start timer must have elapsed and all alarms must be cleared
(see Troubleshooting Guide section on page 43).
When start-up is initiated the status screen displays the start-up
progress and the Start/Stop icon
start-up begins, the PIC 5 control system performs a series of
pre-start tests to verify that all pre-start alerts and safeties are
PANEL LOCATION
within acceptable limits. Table 2 shows appropriate Prestart
HMI Control Panel
Alerts/Alarms conditions. If a test is not successful, the start-up
is delayed or aborted. If the tests are successful, the start-up
Starter Cabinet
will be in progress and the COMPRESSOR RUN STATUS
Control Panel
shall be "Startup." The control shall then energize the chilled
Control Panel
water/brine pump relay.
Control Panel
Five seconds later, the condenser pump relay energizes. Thirty
Control Panel
seconds later the PIC 5 control system monitors the chilled water
and condenser water flow devices and waits until the WATER
Control Panel
FLOW VERIFY TIME (operator-configured, default 5 minutes)
See Fig. 2 and Fig. 5
expires to confirm flow. After flow is verified, the chilled water
See Fig. 2 and Fig. 5
temperature is compared to CONTROL POINT plus 1/2
CHILLED WATER DEADBAND. If the temperature is less than
or equal to this value, the PIC 5 control system turns off the con-
denser pump relay and goes into a Recycle mode.
If the water/brine temperature is high enough, the start-up se-
quence continues and checks the guide vane position. If the
guide vanes are more than 4% open, the start-up waits until the
11
START-UP/SHUTDOWN/
RECYCLE SEQUENCE
Fig. 6 — Chiller Start/Stop Icon
Unit Start/Stop
Fig. 7 — Local On
blinks green. Once local