Safety Controls; Shunt Trip; Default Screen Freeze - Carrier 19XRV Start-Up, Operation And Maintenance Instructions Manual

19xrv pic iii control hermetic centrifugal liquid chillers
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NOTE: This schedule is for illustration only and is not
intended to be a recommended schedule for chiller
operation.
Whenever the chiller is in the LOCAL mode, it uses
Occupancy Schedule 01 (OCCPC01S). When the chiller is
in the ICE BUILD mode, it uses Occupancy Schedule 0
(OCCPC0S). When the chiller is in CCN mode, it uses
Occupancy Schedule 03 (OCCPC03S).
The CCN SCHEDULE NUMBER is configured on the
NET_OPT display screen, accessed from the EQUIPMENT
CONFIGURATION table. See Table 3, Example 15.
SCHEDULE NUMBER can be changed to any value from
03 to 99. If this number is changed on the NET_OPT screen,
the operator must go to the ATTACH TO NETWORK
DEVICE screen to upload the new number into the
SCHEDULE screen. See Fig. 6.

5.4 - Safety controls

The PIC III monitors all safety control inputs and, if
required, shuts down the chiller or limits the guide vanes
to protect the chiller from possible damage from any of
the following conditions:
high bearing temperature
high motor winding temperature
high discharge temperature
low discharge superheat*
low oil pressure
low cooler refrigerant temperature/pressure
condenser high pressure or low pressure
inadequate water/brine cooler and condenser flow
high, low, or loss of voltage
ground fault
voltage imbalance
current imbalance
excessive motor acceleration time
lack of motor current signal
excessive motor amps
excessive compressor surge
temperature and transducer faults
VFD power faults
VFD over temperature
dew formation on the VFD cold plate
*
Superheat is the difference between saturation tempe-
rature and sensible temperature. The high discharge
temperature safety measures only sensible temperature.
VFD faults or optional protective devices within the VFD
can shut down the chiller.
Caution: If compressor motor overload occurs, check the
motor for grounded or open phases before attempting a
restart.
If the PIC III control initiates a safety shutdown, it displays
the reason for the shutdown (the fault) on the ICVC display
screen along with a primary and secondary message, and
blinks the alarm light on the control panel. The alarm is
stored in memory and can be viewed on the ALARM
HISTORY and VFD_HIST screens on the ICVC, along with
a message for troubleshooting.
36
If the safety shutdown was also initiated by a fault detected
in the VFD, the conditions at the time of the fault will be
stored in VFD_HIST.
To give more precise information or warnings on the
chiller's operating condition, the operator can define alert
limits on various monitored inputs in the SETUP1 screen.
A partial list of protective safety and alert limits is provided
in Table 5. A complete list of alarm and alert messages is
provided in the Troubleshooting Guide section, page 54.

5.5 - Shunt trip

The function of the shunt trip on the PIC III is to act as a
safety trip. The shunt trip is wired from the standard I/O
board to a VFD circuit breaker. If the PIC III tries to shut
down the compressor using a normal shutdown procedure
but is unsuccessful for 0 seconds, the shunt trip output is
energised and causes the circuit breaker to trip off. If ground
fault protection has been applied to the VFD, the ground
fault trip also energises the shunt trip to trip the circuit
breaker. Protective devices in the starter can also energise
the shunt trip. The shunt trip feature can be tested using
the Control Test feature in the DISCRETE OUTPUTS
CONTROL TEST screen. When the VFD circuit breaker
is tripped, there will be a loss of communication with the
gateway (3) alarm.

5.6 - Default screen freeze

When the chiller is in an alarm state, the default ICVC
display "freezes," that is, it stops updating. The first line of
the ICVC default screen displays a primary alarm message;
the second line displays a secondary alarm message.
The ICVC default screen freezes to enable the operator to
see the conditions of the chiller at the time of the alarm. If
the value in alarm is one normally displayed on the default
screen, it flashes between normal and reverse contrast. The
ICVC default screen remains frozen until the condition
that caused the alarm is remedied by the operator. Use
ICVC display and alarm shutdown record sheet (CL-1) to
record all values from default screen freeze.
Knowledge of the operating state of the chiller at the time
an alarm occurs is useful when troubleshooting. Additional
chiller information can be viewed on the status screens and
the VFD_HIST screen. Troubleshooting information is
recorded in the ALARM HISTORY table, which can be
accessed from the SERVICE menu.
To determine what caused the alarm, the operator should
read both the primary and secondary default screen messa-
ges, as well as the alarm history. The primary message
indicates the most recent alarm condition. The secondary
message gives more detail on the alarm condition. Since
there may be more than one alarm condition, another alarm
message may appear after the first condition is cleared.
Check the ALARM HISTORY screen for additional help
in determining the reasons for the alarms. Once all existing
alarms are cleared (by pressing the ReSet softkey), the
default ICVC display returns to normal operation.

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