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A
— START INITIATED — Prestart checks made; evaporator
pump started
B
— Condenser water pump started (5 seconds after A)
C
— Water flows verified (30 seconds to 5 minutes maximum
after B). Chilled water temperatures checked against con-
trol point. Guide vanes checked for closure. Oil pump started;
tower fan control enabled.
D
— Oil pressure verified (15 seconds minimum, 300 seconds
maximum after C)
E
— Compressor motor starts, compressor ontime and service
ontime start, 15-minute inhibit timer starts (10 seconds af-
ter D)
F
— SHUTDOWN INITIATED — Compressor motor stops, com-
pressor ontime and service ontime stops, and 1-minute in-
hibit timer starts.
G
— Oil pump and evaporator pumps deenergized (60 seconds
after F). Condenser pump and tower fan control may con-
tinue to operate if condenser pressure is high. Evaporator
pump may continue if in RECYCLE mode.
O/A — Restart permitted (both inhibit timers expired) (minimum of
15 minutes after E; minimum of 1 minute after F).
Fig. 22 — Control Sequence
When a safety shutdown occurs, the shutdown sequence
first stops the compressor by deactivating the start relay. A
status message of ''SHUTDOWN IN PROGRESS, COM-
PRESSOR DEENERGIZED'' is displayed. 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 will be shut down when the CONDENSER REFRIG-
ERANT 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 machine 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 —
STOP AMPS THRESHOLD closes the guide vanes of the
compressor automatically when 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 or until the guide vane is less than
2% open. The compressor will then shut off.
If the machine enters an alarm state or if the compressor
enters a RECYCLE mode, the compressor will be deener-
gized immediately.
To activate SOFT STOP AMPS THRESHOLD, view the
bottom of Service1 table. Set the SOFT STOPAMPS THRESH-
OLD 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 ap-
plied, a status message ''SHUTDOWN IN PROGRESS, COM-
PRESSOR UNLOADING'' is shown.
Chilled Water Recycle Mode —
cycle off and wait until the load increases to restart again
when the compressor is running in a lightly loaded condi-
tion. This cycling of the chiller is normal and is known as
recycle. A recycle shutdown is initiated when any of the fol-
lowing conditions are present:
• when in LCW control, the LEAVING CHILLED WATER
temperature is more than 5° F (3° C) below the control
point, and the CONTROL POINT has not increased in the
last 5 minutes
• when ECW CONTROL OPTION is enabled, the ENTER-
ING CHILLED WATER temperature is more than 5° F
(3° C) 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 machine is in RECYCLE mode, the chilled wa-
ter pump relay remains energized so that the chilled water
temperature can be monitored for increasing load. The re-
cycle 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 RE-
CYCLE 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 shall ini-
tiate a start-up, with a normal start-up sequence.
An alert condition may be generated if 5 or more RE-
CYCLE STARTUPs occur in less than 4 hours. This exces-
sive recycling can reduce machine life. Compressor recycling
due to extremely low loads should be reduced. To reduce
compressor recycling, use the time schedule to shut the ma-
chine down during low load operation or increase the ma-
chine 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 machine should not be operated below design
minimum load without a hot gas bypass installed on the
machine.
35
The SOFT
The machine may
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