Emerson Vission 20/20 Operation And Service Manual page 169

Appendix B • Vission 20/20 Application Procedures
The master compressor controls the slave compressors
based on the master compressor control setpoints as
well as the setpoints entered in the master compressor
sequencing menu. Page 1 of the master compressor
sequencing menu (see Figure B-8) allows the operator
to view and adjust settings which are used for compres-
sor sequencing. The pressure / temperature control set-
points and capacity load / unload timers to accomplish
sequencing control are defi ned here:
1. Load Rate 2 Offset (Outer)
2. Load Rate 1 Offset (Inner)
3. Suction Pressure / Process Temperature Control
Setpoint
4. Unload Rate 1 Offset (Inner)
5. Unload Rate 2 Offset (Outer)
Load Rate 2 Offset (Outer)
• Defi nes the outer pressure/temperature setpoint
offset to monitor compressor load. If suction pres-
sure / process temperature surpasses the control
Figure B-8. Slave Compressor(s) Loading and Unloading Setup
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 2.0
setpoint + load rate 1 offset and goes beyond the
control setpoint + load rate 2 offset then sequencing
decisions are made according to load rate 2 timer.
Load Rate 1 Offset (Inner)
• Defi nes the inner pressure/temp setpoint offset to
monitor compressor load. If suction pressure / proc
temp surpasses the Control Setpoint + load rate 1
offset then sequencing decisions are made accord-
ing to load rate 1 timer.
Suction Pressure /Process Temperature Control Setpoint
• The target setpoints are read only values here.
These setpoints can be changed by logging on
to "Compressor Control" menu of the Master
Compressor.
Unload rate 1 offset (Inner)
• Defi nes the inner pressure setpoint to monitor com-
pressor unload. If suction pressure / proc temp goes
below the Control Setpoint minus the unload rate 1
offset then sequencing decisions are made accord-
ing to unload rate 1 timer.
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