Service manual

B - 11
Vission 20/20 • Operation and Service Manual •Vilter/Emerson • 35391SC 2.0
Appendix B • Vission 20/20 Application Procedures
Vission 20/20 Compressor Sequencing
Setup
SCOPE
Vission 20/20 programs – version 4550.1 and later
OVERVIEW
Compressor sequencing in the Vission 20/20 panel is
carried out by utilizing the Ethernet communication
port using Modbus TCP protocol. Future program releas-
es will accommodate using the serial RS-485 Modbus
RTU port. This will give the Vission 20/20 control panel
the ability to sequence Vission control panels acting as
Master Control. All legacy Vission panels will always act
as slaves.
Compressor sequencing is accomplished by the mas-
ter compressor, monitoring its own control parameter
(either suction pressure or process temperature). As
its control parameter changes value, it will make deci-
sions to start, stop, load and unload slave compressors
as needed, to maintain the control setpoint which is de-
fi ned in the master compressor Sequencing screen.
NOTE
The master compressor will ALWAYS be priority #1
compressor – and act as the trim compressor. So this
must be taken into account when deciding which
compressor is to act as the master compressor.
The following discussion assumes that the physical
Ethernet network has been installed between all Vission
20/20 control panels.
CONFIGURATION OVERVIEW
MASTER COMPRESSOR CONTROL SETPOINTS
SETUP
Navigate to the Compressor Control menu of the Master
Compressor – page 1, see Figure B-6. The “Pressure
Control Setpoint” setting defi nes the control setpoint
for the entire sequencing system. The capacity in-
crease and capacity decrease proportional control set-
tings defi ne the loading and unloading settings for the
Figure B-6. Master Compressor Loading, Unloading and Auto-cycle Setpoints Setup