Specifications

45
STAT display screen). It cannot be started or run during an un-
occupied time period (when OCCUPIED? is set to NO on the
MAINSTAT 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
OCCUPIED? is YES, unless an unoccupied time period is in
effect.
These schedules can be set up to follow a building’s occu-
pancy schedule, or the chiller can be set so to run 100% of the
time, if the operator wishes. The schedules also can be by-
passed by forcing the CHILLER START/STOP parameter on
the MAINSTAT screen to START. For more information on
forced starts, see Local Start-Up, page 62.
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 23.
Figure 20 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). When the chiller is in the
ICE BUILD mode, it uses Occupancy Schedule 02
(OCCPC02S). When the chiller is in CCN mode, it uses Occu-
pancy Schedule 03 (OCCPC03S). The default setting for both
LOCAL and CCN schedules is OCCUPIED all of the time.
The CCN SCHEDULE NUMBER is configured on the
NET_OPT display screen, accessed from the EQUIPMENT
CONFIGURATION table. See Table 3, Example 17. 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
upload the new number into the SCHEDULE screen. See
Fig. 19.
Safety Controls — The PIC II 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 condenser water pressure drop (optional)
• high, low, or loss of voltage
• ground fault
• voltage imbalance
• current imbalance
• excessive motor acceleration time
• excessive starter transition time
• lack of motor current signal
• excessive motor amps
• excessive compressor surge
• temperature and transducer faults
*Superheat is the difference between saturation temperature
(CONDENSER REFRIGERANT TEMPERATURE) and
sensible temperature (COMPRESSOR DISCHARGE TEM-
PERATURE). The high discharge temperature safety mea-
sures only sensible temperature.
Faults or protective devices within the optional VFD can
shut down the chiller.
If the PIC II 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, energizes
an alarm relay in the starter, and blinks the alarm light on the
control panel. The alarm is stored in memory and can be
viewed on the ALARM HISTORY and ISM_HIST screens on
the ICVC, along with a message for troubleshooting. If the
safety shutdown was also initiated by a fault detected in the
motor starter, the conditions at the time of the fault will be
stored in ISM_HIST.
To give more precise information or warnings on the chill-
er’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 provided in the
Troubleshooting Guide section on page 99.
Pump and Fan Control — The Carrier PIC controls
are designed to control when cooler and condenser water
pumps and tower fans are turned on and off. This is accom-
plished through a series of relay contacts on the ISM within the
starter or optional VFD, and interface terminals are provided at
ISM terminal strip J9 (refer to the Carrier Installation Instruc-
tions and certified drawings). If primary control of water
pumps and tower fans is provided by customer-installed devic-
es, a parallel means for the Carrier controls to independently
operate the pumps and fans must also be provided to protect
against freeze-up.
Shunt Trip (Option) — A main circuit breaker shunt trip
device is provided standard as a safety trip with all unit-mount-
ed starters, and is optional on other starters and some VFDs.
When a shunt trip is provided, it is wired from an output on the
ISM to the associated coil on the shunt trip equipped motor cir-
cuit breaker. The shunt trip is activated by ISM logic, based on
values entered in the ISM_CONF table, under any of the fol-
lowing conditions:
• Motor locked rotor amps limit exceeded
• Starter locked rotor amps rating exceeded
• Ground fault or phase-to-phase current fault limit
exceeded (when that option is included)
• Significant motor current detected more than 20 seconds
after a shutdown or otherwise when the chiller is off
• 1M and 2M auxiliary contacts closed when the chiller is
off.
In addition, starters may be designed to shunt trip based on
other starter-specific conditions or features. For example, Ben-
shaw solid state starters include several such protective circuits.
The shunt trip is also activated if EVAPORATOR PRESSURE
drops below 0 psig (0 kPa). The Shunt Trip feature can be test-
ed using the Control Test feature.
Function Loss Trip — The Function Loss Trip device
is provided standard as a safety trip with all unit-mounted
VFDs. When provided, the function loss trip is wired from an
output on the ISM to the VFD regulator board on the function
loss terminal. The function loss trip is activated by ISM logic,
based on values entered in the ISM _ CONF table.
CAUTION
If compressor motor overload occurs, check the motor for
grounded or open phases before attempting a restart.