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

The chiller also maintains a start-to-start timer and a
stop-to-start timer. These timers limit how soon the chiller
can be started. START INHIBIT TIMER is displayed on
the MAINSTAT screen. See the Start-Up/Shutdown/Recycle
Sequence section, page 53, for more information on this topic.
OCCUPANCY SCHEDULE — The chiller schedule, de-
scribed in the Time Schedule Operation section (page 24), deter-
mines when the chiller can run. Each schedule consists of from
1 to 8 occupied or unoccupied time periods, set by the operator.
The chiller can be started and run during an occupied time
period (when OCCUPIED? is set to YES on the MAINSTAT
display screen). It cannot be started or run during an unoccupied
time period (when OCCUPIED? is set to NO on the MAIN-
STAT display screen). These time periods can be set for each
day of the week and for holidays. The day begins with 0000
hours and ends with 2400 hours. The default setting for OCCU-
PIED? is YES, unless an unoccupied time period is in effect.
These schedules can be set up to follow a building's
occupancy schedule, or the chiller can be set so to run 100% of
the time, if the operator wishes. The schedules also can be
bypassed by forcing the CHILLER START/STOP parameter on
the MAINSTAT screen to START. For more information on
forced starts, see Local Start-Up, page 53.
The schedules also can be overridden to keep the chiller in
an occupied state for up to 4 hours, on a one time basis. See the
Time Schedule Operation section, page 24.
Figure 19 shows a schedule for a typical office building
with a 3-hour, off-peak, cool-down period from midnight to
3 a.m., following a weekend shutdown. Holiday periods are in
an unoccupied state 24 hours per day. The building operates
Monday through Friday, 7:00 a.m. to 6:00 p.m., and Saturdays
from 6:00 a.m. to 1:00 p.m. This schedule also includes the
Monday midnight to 3:00 a.m. weekend cool-down schedule.
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 02
(OCCPC02S). 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 4, Example 15. SCHED-
ULE 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 up-
load the new number into the SCHEDULE screen. See Fig. 17.
The PIC III monitors all safety con-
Safety Controls —
trol 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 temperature
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.
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. 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 6. A complete list of alarm and alert messages is pro-
vided in the Troubleshooting Guide section, page 82.
The function of the shunt trip on the PIC III
Shunt Trip —
is to act as a safety trip. The shunt trip is wired from the stan-
dard 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 20 seconds, the shunt trip output is ener-
gized and causes the circuit breaker to trip off. If ground fault
protection has been applied to the VFD, the ground fault trip
also energizes the shunt trip to trip the circuit breaker. Protec-
tive devices in the starter can also energize 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 com-
munication with the gateway (223) alarm.
Default Screen Freeze —
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-12) 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 messages, 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
softkey), the default ICVC display returns to normal operation.
39
When the chiller is in an alarm
RESET