Specifications

64
Shutdown Sequence — Chiller shutdown begins if
any of the following occurs:
• the STOP button is pressed continuously for at least one
second (the alarm light blinks once to confirm the stop
command)
• a recycle condition is present (see Chilled Water Recycle
Mode section)
• the time schedule has gone into unoccupied mode
• the chiller protective limit has been reached and chiller is
in alarm
• the start/stop status is overridden to stop from the CCN
network or the ICVC
When a stop signal occurs, the shutdown sequence first
stops the compressor by deactivating the start relay (1CR). A
status message of “SHUTDOWN IN PROGRESS, COM-
PRESSOR DEENERGIZED” is displayed, and the compres-
sor ontime and service ontime stop. The guide vanes are then
brought to the closed position. The oil pump relay and the
chilled water/brine pump relay shut down 60 seconds after the
compressor stops. The condenser water pump shuts down at
the same time if the ENTERING CONDENSER WATER tem-
perature is greater than or equal to 115 F (46.1 C) and the
CONDENSER REFRIG TEMP is greater than the CONDENS-
ER FREEZE POINT plus 5 F (–15.0 C). The stop-to-start timer
now begins to count down. If the start-to-start timer value is
still greater than the value of the start-to-stop timer, then this
time displays on the ICVC.
Certain conditions that occur during shutdown can change
this sequence.
• If the AVERAGE LINE CURRENT is greater than 5%
after shutdown, or the starter contacts remain energized,
the oil pump and chilled water pump remain energized,
the SHUNT TRIP relay is energized, and the alarm is
displayed.
• The condenser pump shuts down when the CON-
DENSER PRESSURE is less than the COND PRESS
OVERRIDE threshold minus 3.5 psi (24.1 kPa) and the
CONDENSER REFRIG TEMP is less than or equal to the
ENTERING CONDENSER WATER temperature plus
3 F (–1.6 C).
• If the chiller shuts down due to low refrigerant tempera-
ture, the chilled water pump continues to run until the
LEAVING CHILLED WATER temperature is greater than
the CONTROL POINT temperature, plus 5 F (3 C).
Automatic Soft Stop Amps Threshold — The
soft stop amps threshold feature closes the guide vanes of the
compressor automatically if a non-recycle, non-alarm stop sig-
nal occurs before the compressor motor is deenergized.
Any time the compressor is directed to STOP (except in the
cases of a fault or recycle shutdown), the guide vanes are di-
rected to close, and the compressor shuts off when any of the
following is true:
• AVERAGE LINE CURRENT (%) drops below the SOFT
STOP AMPS THRESHOLD
• ACTUAL GUIDE VANE POSITION drops below 4%
• 4 minutes have elapsed
• the STOP button is pressed twice
If the chiller enters an alarm state or if the compressor enters
a RECYCLE mode, the compressor deenergizes immediately.
To activate the soft stop amps threshold feature, scroll to the
bottom of OPTIONS screen on the ICVC. Use
the or softkey to set the SOFT
STOP AMPS THRESHOLD parameter to the percent of amps
at which the motor will shut down. The default setting is 100%
amps (no soft stop). The range is 40 to 100%.
When the soft stop amps threshold feature is being applied,
a status message, “SHUTDOWN IN PROGRESS, COM-
PRESSOR UNLOADING” displays on the ICVC.
The soft stop amps threshold function can be terminated and
the compressor motor deenergized immediately by depressing
the STOP button twice.
Chilled Water Recycle Mode — The chiller may
cycle off and wait until the load increases to restart when the
compressor is running in a lightly loaded condition. This cy-
cling is normal and is known as “recycle.” A recycle shutdown
is initiated when any of the following conditions are true:
• LEAVING CHILLED WATER temperature (or ENTERING
CHILLED WATER temperature, if the ECW CONTROL
OPTION is enabled) is more than 5° F (2.8° C) below the
CONTROL POINT.
• LEAVING CHILLED WATER temperature (or ENTERING
CHILLED WATER temperature, if the ECW CONTROL
OPTION is enabled) is below the CONTROL POINT, and
the chilled water temperature difference is less than the
(RECYCLE CONTROL) SHUTDOWN DELTA T (config-
ured in the EQUIPMENT SERVICE/SETUP1 table).
•the LEAVING CHILLED WATER temperature is within
3 F (1.7 C) of the EVAP REFRIG TRIPPOINT.
NOTE: Recycle shutdown will not occur if the CONTROL
POINT has been modified (e.g., by a chilled water reset input)
within the previous 5 minutes of operation. Also, chilled water
recycle logic does not apply to Ice Build operation.
When the chiller is in RECYCLE mode, the chilled water
pump relay remains energized so the chilled water temperature
can be monitored for increasing load. The recycle control uses
RESTART DELTA T to check when the compressor should be
restarted. This is an operator-configured function which de-
faults to 5 F (3 C). This value can be viewed or modified on
the SETUP1 table. The compressor will restart when the chiller
is:
• in LCW CONTROL and the LEAVING CHILLED
WATER temperature is greater than the CONTROL
POINT plus the RECYCLE RESTART DELTA T.
•in ECW CONTROL and the ENTERING CHILLED
WATER temperature is greater than the CONTROL
POINT plus the RECYCLE RESTART DELTA T.
Once these conditions are met, the compressor initiates a
start-up with a normal start-up sequence.
An alert condition may be generated if 5 or more recycle
start-ups occur in less than 4 hours. Excessive recycling can
reduce chiller life; therefore, compressor recycling due to ex-
tremely low loads should be reduced.
To reduce compressor recycling, use the time schedule to
shut the chiller down during known low load operation period,
or increase the chiller load by running the fan systems. If the
hot gas bypass is installed, adjust the values to ensure that hot
gas is energized during light load conditions. Increase the
RECYCLE RESTART DELTA T on the SETUP1 table to
lengthen the time between restarts.
The chiller should not be operated below design minimum
load without a hot gas bypass installed.
Safety Shutdown — A safety shutdown is identical to a
manual shutdown with the exception that, during a safety shut-
down, the ICVC displays the reason for the shutdown, the
alarm light blinks continuously, and the spare alarm contacts
are energized.
After a safety shutdown, the softkey must be
pressed to clear the alarm. If the alarm condition is still present,
the alarm light continues to blink. Once the alarm is cleared,
the operator must press the or softkeys to re-
start the chiller.
INCREASE
DECREASE
RESET
CCN
LOCAL