Shutdown Sequence; Automatic Soft-Stop Amps Threshold; (Psio Software Version 09 And Higher); Chilled Water Recycle Mode - Carrier 19XL Start-Up, Operation And Maintenance Instructions Manual

and go into a RECYCLE mode. If the water/brine tempera-
ture is high enough, the start-up sequence continues on to
check the guide vane position. If the guide vanes are more
than 6% open, the start-up waits until the PIC closes the vanes.
If the vanes are closed, and the oil pump pressure is less
than 3 psid (21 kPad), the oil pump relay will then be en-
ergized. The PIC then waits until the OIL PRESS (Pressure)
VERIFY TIME (operator configured, default 15 seconds) for
oil pressure to reach 18 psid (124 kPad). After oil pressure
is verified, the PIC waits 15 seconds, and then the compres-
sor start relay (1CR) is energized to start the compressor.
Compressor ontime and service ontime timers start and the
compressor starts counter and the number of starts over a
12-hour period counter are advanced by one.
Failure to verify any of the requirements up to this point
will result in the PIC aborting the start and displaying the
applicable pre-start mode of failure on the LID default screen.
A pre-start failure does not advance the starts in 12 hours
counter. Any failure, after the 1CR relay has energized, re-
sults in a safety shutdown, energizes the alarm light, and dis-
plays the applicable shutdown status on the LID display.
Shutdown Sequence —
occur if any of the following events happen:
• the STOP button is pressed for at least one second (the
alarm light will blink once to confirm stop command)
• recycle condition is present (see Chilled Water Recycle Mode
section)
• time schedule has gone into UNOCCUPIED mode (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 LID
When a stop signal occurs, the shutdown sequence first
stops the compressor by deactivating the start relay. A status
message of ''SHUTDOWN IN PROGRESS, COMPRES-
SOR DEENERGIZED'' is displayed. Compressor 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 are shut down 60 seconds after the com-
pressor stops. The condenser water pump will be shut down
when the CONDENSER REFRIGERANT TEMP is less than
the CONDENSER PRESSURE OVERRIDE minus 5 psi
(34 kPa) or is less than or equal to the ENTERING
CONDENSER WATER TEMP plus 3° F (2° C). The stop-
to-start timer will now begin to count down. If the start-to-
start timer is still greater than the value of the start-to-stop
timer, then this time is now displayed on the LID.
Certain conditions during shutdown will change this
sequence:
• if the COMPRESSOR MOTOR LOAD 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 temperature is
greater than 115 F (46 C) at shutdown, the condenser pump
will be deenergized after the 1CR compressor start relay
• if the chiller shuts down due to low refrigerant tempera-
ture, the chilled water pump will stay running until the
LEAVING CHILLED WATER is greater than CONTROL
POINT, plus 5° F (3° C)
Automatic Soft Stop Amps Threshold (PSIO Soft-
ware Version 09 and Higher) —
AMPS THRESHOLD closes the guide vanes of the com-
pressor automatically when a non-recycle, non-alarm stop
signal occurs before the compressor motor is deenergized.
Shutdown of the chiller can
The SOFT STOP
If the STOP button is pressed, the guide vanes close to a
preset amperage percent or until the guide vane is less than
2% open. The compressor will then shut off.
If the chiller enters an alarm state or if the compressor
enters a RECYCLE mode, the compressor will be de-
energized immediately.
To activate SOFT STOP AMPS THRESHOLD, view
the bottom of Service1 table. Set the SOFT STOP AMPS
THRESHOLD value to the percentage amps at which the
motor will shut down. The default setting is 100% amps (no
Soft Stop).
When the SOFT STOP AMPS THRESHOLD is being
applied, a status message ''SHUTDOWN IN PROGRESS,
COMPRESSOR UNLOADING'' is shown.
Chilled Water Recycle Mode —
off and wait until the load increases to restart again when
the compressor is running in a lightly loaded condition. This
cycling of the chiller is normal and is known as recycle. A
recycle shutdown is initiated when any of the following con-
ditions are true:
• when in LCW control, the difference between the LEAV-
ING CHILLED WATER temperature and ENTERING
CHILLED WATER temperature is less than the RECYCLE
SHUTDOWN DELTA T (found in the Service1 table) and
the LEAVING CHILLED WATER TEMP is below the
CONTROL POINT, and the CONTROL POINT has not
increased in the last 5 minutes.
• when 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
Service1 table) and the ENTERING CHILLED WATER
TEMPERATURE is below the CONTROL POINT, and the
CONTROL POINT has not increased in the last 5 minutes.
• when the LEAVING CHILLED WATER temperature is within
3° F (2° C) of the BRINE REFRIG TRIPPOINT
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 RECYCLE RESTART DELTA T to check when
the compressor should be restarted. This is an operator-
configured function which defaults to 5° F (3° C). This value
is viewed/modified on the Service1 table. The compressor
will restart when:
• in LCW CONTROL the LEAVING CHILLED WATER tem-
perature is greater than the CONTROL POINT plus the
RECYCLE RESTART DELTA T; or
• in ECW CONTROL, the ENTERING CHILLED WATER
temperature is greater than the CONTROL POINT plus the
RECYCLE RESTART DELTA T
Once these conditions are met, the compressor will ini-
tiate a start-up, with a normal start-up sequence.
An alert condition may be generated if 5 or more
RECYCLE STARTUPs occur in less than 4 hours. This
excessive recycling can reduce chiller life. Compressor re-
cycling due to extremely low loads should be reduced. To
reduce compressor recycling, use the time schedule to shut
the chiller down during 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 ener-
gized during light load conditions. Increase the RECYCLE
RESTART DELTA T on the Service1 table to lengthen the
time between restarts.
The chiller should not be operated below design mini-
mum load without a hot gas bypass installed on the
chiller.
40
The chiller may cycle