88
CDHH-SVX003C-EN
If the chilled water temperature drops below the chilled
water setpoint 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 Symbio™ 800
monitors leaving chilled water temperature, preparing
for the next compressor motor start based on the
differential to start setpoint.
The following figure (satisfied setpoint) illustrates this
sequence.
Figure 61. 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 62. 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 3 psid (20.7 kPaD)
Start-up and Shutdown
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