Filter
Top Products
47
Shutdown Sequence —
Chiller shutdown begins if
any of the following occurs:
• the STOP button is pressed 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 CVC/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 CVC/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
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 com-
pressor automatically if a non-recycle, non-alarm stop signal
occurs before the compressor motor is deenergized.
If the STOP button is pressed, the guide vanes close to a
preset amperage percent until the guide vane is less than 4%
open or 4 minutes have passed. The compressor then shuts off.
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 CVC/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 CVC/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:
• the chiller is in LCW control, the difference between the
LEAVING CHILLED WATER temperature and ENTER-
ING CHILLED WATER temperature is less than the
RECYCLE SHUTDOWN DELTA T (found in the
SETUP1 table) the LEAVING CHILLED WATER tem-
perature is 5° F (2.8° C) below the CONTROL POINT,
the CONTROL POINT has not increased in the last
5 minutes and ICE BUILD is not active.
• the ECW CONTROL OPTION is enabled, the difference
between the ENTERING CHILLED WATER temperature
and the LEAVING CHILLED WATER temperature is less
than the RECYCLE SHUTDOWN DELTA T (found in the
SETUP1 table), the ENTERING CHILLED WATER tem-
perature is 5° F (2.8° C) below the CONTROL POINT,
and the CONTROL POINT has not increased in the last
5 minutes.
• the LEAVING CHILLED WATER temperature is within
3° F (2° C) of the EVAP REFRIG TRIPPOINT.
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
shutdown, the CVC/ICVC displays the reason for the shut-
down, 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