If any of these requirements are not met, the PIC aborts
the start and displays the applicable pre-start mode of failure
on the LID default screen. A pre-start failure does not ad-
vance the STARTS IN 12 HOURS counter (STATUS01 screen).
Any failure after the 1CR relay has energized causes a safety
shutdown, advances the STARTS IN 12 HOURS counter by
one, and displays the applicable shutdown status on the LID
display.
Shutdown Sequence —
The chiller shuts down if any
of the following occurs:
• the STOP button on the control panel 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 OCCUPIED ? parameter on the STATUS01 screen reads
NO; that is, the chiller is not scheduled to run at the cur-
rent time and date.
• the remote contact opens.
• the CHILLER START/STOP status is overridden to STOP
from the CCN network or the LID.
When a stop signal occurs, the shutdown sequence first
stops the compressor by deactivating the start relay. A status
message, SHUTDOWN IN PROGRESS, COMPRESSOR
DEENERGIZED, displays. The guide vanes are then brought
to the closed position. The oil pump relay and the chilled
water/brine pump relay are shut down 60 seconds after the
compressor stops. The condenser water pump shuts down
when the condenser refrigerant temperature is less than the
condenser pressure override minus 5 psi (34 kPa) or is less
than or equal to the entering condenser water temperature
plus 3° F (2° C). The stop-to-start timer now begins to count
down. If the value of the start-to-start timer is still greater
than the value of the start-to-stop timer, then the start-to-
start time is displayed on the LID.
There are certain conditions during shutdown that can change
this sequence:
• if the COMPRESSOR MOTOR LOAD (STATUS01 screen)
is greater than 10% after shutdown or the starter contacts
remain energized, the oil pump and chilled water pump
remain energized and the alarm is displayed
• if the ENTERING CONDENSER WATER (STATUS01 screen)
temperature is greater than 115 F (46 C) at shutdown, the
condenser pump is deenergized after the 1CR compressor
start relay
• if the chiller shuts down due to low refrigerant tempera-
ture, the chilled water pump keeps running until the LEAV-
ING CHILLED WATER temperature is greater than the
WATER/BRINE CONTROL POINT plus 5° F (3° C).
Automatic Soft Stop Amps Threshold —
The au-
tomatic soft stop amps threshold is an operator configured
value that closes the guide vanes of the compressor auto-
matically when a non-recycle, non-alarm stop signal occurs
before the compressor motor is deenergized.
If the STOP button on the control panel is pressed, the
guide vanes close to a preset amperage percent or until the
guide vane is less than 2% open. The compressor then shuts
off.
If the chiller enters an alarm state or if the compressor
enters a RECYCLE mode, the compressor is deenergized
immediately.
To activate the automatic soft stop amps threshold, access
the SERVICE1 screen. Set the SOFT STOP AMPS THRESH-
OLD parameter value to the percent of amps at which the
motor will shut down. The default setting is 100% amps (no
soft stop).
When the automatic soft stop amps threshold is being ap-
plied, a status message, SHUTDOWN IN PROGRESS, COM-
PRESSOR UNLOADING, displays.
Chilled Water Recycle Mode —
When the compres-
sor is running under light load conditions, the chiller
may cycle off and wait until the load increases to restart
again. This cycling is normal and is known as recycle. A
recycle shutdown is initiated when any of the following
occurs:
• when the chiller is operating under the control of the leav-
ing chilled water temperature (that is, when the ECW CON-
TROL OPTION on the CONFIG screen is disabled), the
difference between the LEAVING CHILLED WATER tem-
perature and ENTERING CHILLED WATER temperature
is less than the RECYCLE SHUTDOWN DELTA T (found
in the SERVICE1 table) and the LEAVING CHILLED WA-
TER TEMP is below the WATER/BRINE CONTROL POINT,
and the WATER/BRINE CONTROL POINT has not in-
creased in the last 5 minutes
• when the chiller is operating under the control of the en-
tering chilled water temperature (that is, the ECW CON-
TROL OPTION is enabled), the difference between the
ENTERING CHILLED WATER temperature and the LEAV-
ING CHILLED WATER temperature is less than the
RECYCLE SHUTDOWN DELTA T (found in the SERV-
ICE1 table) and the ENTERING CHILLED WATER tem-
perature is below the WATER/BRINE CONTROL POINT,
and the WATER/BRINE CONTROL POINT has not in-
creased in the last 5 minutes
• when the LEAVING CHILLED WATER temperature is within
3° F (2° C) of the BRINE REFRIG TRIPPOINT.
(See the SERVICE1 screen.)
When the chiller is in RECYCLE mode, the chilled water
pump relay remains energized so that the chilled water tem-
perature can be monitored for increasing load. The recycle
control uses the RECYCLE RESTART DELTA T value
to check when the compressor should be restarted. This is an
operator-configured value that defaults to 5° F (3° C). The
value can be viewed/modified on the SERVICE1 screen. The
compressor restarts when:
• the chiller is operating under leaving chilled water tem-
perature control and the LEAVING CHILLED WATER
temperature is greater than the WATER/BRINE CON-
TROL POINT plus the RECYCLE RESTART DELTA T; or
• the chiller is operating under entering chilled water tem-
perature control and the ENTERING CHILLED WATER
temperature is greater than the WATER/BRINE CON-
TROL 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 recycles
occur in less than 4 hours. Because excessive recycling can
reduce chiller life, compressor recycling caused by ex-
tremely low loads should be reduced. To accomplish this,
use the time schedule to shut the chiller down during periods
of known low load operation 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 value on the SERVICE1 screen to lengthen the time be-
tween restarts.
The chiller should not be operated below design mini-
mum load without a hot gas bypass installed on the
chiller.
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