Start-up and Shut-down
CVHH-SVX001A-EN 77
Now that the compressor motor is running in the “ Delta”
configuration, the inlet guide vanes will modulate,
opening and closing to the chiller load variation by
operation of the stepper vane motor actuator to satisfy
chilled water setpoint. The chiller continues to run in its
appropriate mode of operation: Normal, Softload, Limit
Mode, and so on (see
Figure 43). If the oil tank tem perature
rises above the oil cooler setpoint while the compressor is
running, the oil cooler solenoid valve shall be energized to
cool the oil.
If the chilled water temperature drops below the chilled
water set point by an amount set as the “ differential to
stop” setpoint, a normal chiller stop sequence is initiated
as follows:
1. The inlet guide vanes are driven closed (up to
50 seconds).
2. After the inlet guide vanes are closed, the stop relay
and the condenser water pump relays open to turn off.
The oil and refrigerant pump motor will continue to run
for 3 minutes post-lube while the compressor coasts to
a stop. The oil vent line valve will then open. The chilled
water pump will continue to run while the main
processor module monitors leaving chilled water
temperature preparing for the next compressor motor
start based on the “ differential to start” setpoint.
Figure 44, p. 77 illustrates this sequence.
Figure 43. Sequence of operation: running
Starter
Status is
“Running”
Limit Mode
Exit
Limit Mode
Chiller
Is
Running
Starting
Compressor
Chiller Is Running
Chiller Is Running—Limit Chiller Is Running
Modulate IGV/AFD
for LWT control
Modulate IGV/AFD
for LWT control
Modulate IGV/AFD
for Limit control
Enforce All Running Mode Diagnostics
Note: If the Oil Tank Temperature rises above the Oil Cooler Control Setpoint whilte the
compressor is running, the Oil Cooler Solenoid Valve shall be energized to cool the unit.
Figure 44. Sequence of operation: satisfied setpoint
Satisfied Setpoint
Preparing Shutdown
Shutting Down Shutting Down
Running Auto
Close IGV (0–50 sec)
Postlube 3 min
De-Energize Oil Pump
Command IGV Closed
De-Energize
Compressor
Open Oil Vent Line Valve
Confirm No Oil Pressure*
5 min after oil pump is de-energized
Confirm No Compressor Currents
Within 0–30 sec
Hold position of Oil Vent Line Valve
De-Energize Condenser
Water Pump Relay
Enforce All Running Mode Diagnostics
*Note: No oil pressure is less than 20.7 kPad (3 psid)
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