Occupancy Schedule; Safety Controls; Shunt Trip; Default Screen Freeze - Carrier AquaEdge 23XRV 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 MAIN-
STAT screen. See the Start-Up/Shutdown/Recycle Sequence
section, page 60, for more information on this topic.
OCCUPANCY SCHEDULE — The chiller schedule, de-
scribed in the Time Schedule Operation section (page 28),
determines 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 YES is displayed next to OCCUPIED? on
the MAINSTAT display screen). It cannot be started or run
during an unoccupied time period (when NO is displayed next
to OCCUPIED? on the MAINSTAT display screen). These
time periods can be set for each day of the week and for holi-
days. The day begins with 0000 hours and ends with
2400 hours. When any occupancy schedule is in a time period
when the chiller is allowed to run, the parameter OCCUPIED?
is YES.
These schedules can be set up to follow a building's occu-
pancy schedule, or can be set to be occupied 100% of the time,
if the operator wishes. In this case, the chiller is normally
started and stopped manually using the CCN, LOCAL, and
STOP buttons. 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 60.
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 28.
Figure 29 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 Occu-
pancy Schedule 01 (OCCPC01S). The chiller uses Occupancy
Schedule 02 (OCCPCO2S) when it is in ICE BUILD mode.
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.
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. 29.
The PIC III control system monitors
Safety Controls —
all safety control inputs and, if required, shuts down the chiller
or limits the compressor speed to protect the chiller from possi-
ble damage from any of the following conditions:
• high motor winding temperature
• high discharge temperature
• low oil pressure
• low evaporator refrigerant temperature
• condenser high pressure or low pressure
• inadequate liquid/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
See Table 3, Example 18.
• motor stall
• temperature sensor and transducer faults
• VFD power faults
• VFD over temperature
• humidity surrounding the VFD coldplate
• reverse compressor rotation
• incorrect condenser level (for EXV controlled units)
• economizer pressure out of range (for EXV controlled
units)
• economizer temperature out of range (for EXV con-
trolled units)
VFD faults or protective devices within the VFD can shut
down the chiller.
If compressor motor overload or a motor ground fault
occurs, check the motor for grounded or open phases
before attempting a restart to avoid damage to the equip-
ment.
If the PIC III control initiates a safety shutdown, it displays
the reason for the shutdown (the fault code) on the ICVC dis-
play screen along with a primary and secondary message, and
blinks the alarm light on the control center. 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 lim-
its on various monitored inputs in the SETUP1 screen. Safety
contact and alert limits are defined in Table 5. Alarm and alert
messages are listed in the Troubleshooting Guide section,
page 96.
The function of the shunt trip on the PIC III
Shunt Trip —
control module is to act as a safety trip. The shunt trip is wired
from the standard I/O board to a shunt trip-equipped VFD cir-
cuit breaker. If the PIC III module tries to shut down the com-
pressor using a normal shutdown procedure but is unsuccessful
for 20 seconds, the shunt trip output is energized and causes the
circuit breaker to trip off. The ground fault trip also will ener-
gize the shunt trip to trip the circuit breaker. Protective devices
in the VFD can also energize the shunt trip. The shunt trip fea-
ture can be tested using the Control Test feature in the DIS-
CRETE OUTPUTS CONTROL TEST screen. Reset the cir-
cuit breaker immediately after performing this test.
Default Screen Freeze —
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,
the value flashes between normal and reverse contrast. The
ICVC default screen remains frozen until the condition that
caused the alarm is remedied by the operator.
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 VF-
D_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
47
CAUTION
When the chiller is in an