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
than6% 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)
VERIFYTIME (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
applicablepre-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-
sultsin a safety shutdown, energizes the alarm light, and dis-
plays the applicable shutdown status on the LID display.
Shutdown Sequence — Shutdown of the chiller can
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)
• recyclecondition is present (see Chilled Water Recycle Mode
section)
• timeschedule 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
stopsthe compressor by deactivating the start relay. A status
message of ‘‘SHUTDOWN IN PROGRESS, COMPRES-
SORDEENERGIZED’’ is displayed. Compressor ontime and
serviceontime 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 MOTORLOAD is greater than 10%
after shutdown, or the starter contacts remain energized,
theoil pump and chilled water pump remain energized and
the alarm is displayed
• if the ENTERING CONDENSER WATER temperature is
greaterthan 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 WATERis greater than CONTROL
POINT, plus 5° F (3° C)
AutomaticSoft Stop Amps Threshold (PSIO Soft-ware Version 09 and Higher) — The SOFT STOP
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.
If the STOPbutton 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
motorwill 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.
ChilledWater Recycle Mode — The chiller may cycle
off and wait until the load increases to restart again when
thecompressor is running in a lightly loaded condition. This
cycling of the chiller is normal and is known as recycle. A
recycleshutdown 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
CHILLEDWATER temperature is less than the RECYCLE
SHUTDOWN DELTAT (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.
• whenECW CONTROLOPTION is enabled, the difference
between the ENTERING CHILLED WATERtemperature
and the LEAVING CHILLED WATERtemperature is less
than the RECYCLE SHUTDOWN DELTAT (found in the
Service1 table) and the ENTERING CHILLED WATER
TEMPERATUREis below the CONTROL POINT, and the
CONTROLPOINT has not increased in the last 5 minutes.
• whenthe LEAVING CHILLED WATERtemperature is within
3° F (2° C) of the BRINE REFRIG TRIPPOINT
Whenthe chiller is in RECYCLE mode, the chilled water
pump relay remains energizedso that the chilled water tem-
perature can be monitored for increasing load. The recycle
control uses RECYCLE RESTARTDELTA T to check when
the compressor should be restarted. This is an operator-
configuredfunction which defaults to 5° F (3° C). This value
is viewed/modified on the Service1 table. The compressor
will restart when:
• inLCW CONTROL the LEAVING CHILLED WATERtem-
perature is greater than the CONTROL POINT plus the
RECYCLE RESTART DELTAT; or
• in ECW CONTROL, the ENTERING CHILLED WATER
temperatureis greater than the CONTROL POINT plus the
RECYCLE RESTART DELTAT
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
chillerload 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 DELTAT 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