19 – 3
Section 19 • Compressor Sequencing
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3
Suction Pressure Control Setpoint
The Compressor sequencing screen denes settings
that are used by the compressor for sequencing. The
Suction Pressure Sequencing Control mode can be se-
lected from the Radio Button. There is warning dialog
asking for the change in sequencing control mode leads
the compressor to go out of sequencing. For Suction
Pressure Control Setpoints see Figure 19-2 and for the
warning see Figure 19-3.
Setpoint:
• The suction pressure of the compressor to operate
when the compressor is running in Auto Sequencing
mode.
Start Offset:
• Denes the offset from suction pressure control set-
point to start compressor. If suction pressure sur-
passes start offset setpoint and compressor capacity
has reached max, then the sequencing algorithm al-
lows the starting and loading of compressors to cater
for increasing load requirements. The lead compres-
sor should bypass this setpoint(i.e. should not wait
for start time period when suction pressure is below
setpoint + start offset).
Stop Offset:
• Denes the offset from suction pressure control set-
point to stop compressor. If suction pressure surpass-
es stop offset setpoint and compressor capacity has
reached min, then the sequencing algorithm allows
the stop and unloading of compressor to cater for de-
creasing load requirements. The lead compressor in
sequencing should bypass this offset (i.e should not
stop and keep running with min load).
Start Timer:
• If suction pressure surpasses the suction pressure
control setpoint then this timer’s value is used to
make periodic sequencing decisions.
Stop Timer:
• If suction pressure drops below the suction pressure
control setpoint then this timer’s value is used to
make periodic sequencing decisions.
Process Temp. Control Setpoint
The Compressor sequencing screen denes settings
that are used by the compressor for sequencing. The
Process Temperature Sequencing Control mode can be
selected from the Radio Button. There is warning dialog
asking for the change in sequencing control mode leads
the compressor to go out of sequencing. For Process
Temperature Control Setpoints see Figure 19-2 and for
the warning see Figure 19-3.
Setpoint:
• The process temperature of the compressor to
operate when the compressor is running in Auto
Sequencing mode.
Figure 19-2. Compressor Sequencing Screen – Setpoints Conguration
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