Emerson VILTER MicroVission Operation And Service Manual page 65

Section 5 • Compressor Control
Pulldown:
This checkbox enables the Pulldown feature. If this
checkbox is unchecked, the Pulldown setpoints are
ignored and the user is not allowed to edit them. The
Pulldown setpoints are dependent on the Active Control
Mode Selection. If Suction Pressure is selected, then
the Pulldown setpoint are in Pressure values or Process
Control is selected then the Pulldown setpoints are in
Temperature values. See Figure 5-14 and 5-15.
Initiate Pulldown at Next Start/Every Start:
If Initiate Pulldown at Next Start is selected, then
Pulldown Operation will start at the next compressor
start cycle only, and Pulldown feature will disable af-
ter the Pulldown Operation is completed. But if Initiate
Pulldown at Every Start is selected, then Pulldown
Operation will start at every compressor start cycle.
Only one of the options can be selected.
Step Pressure / Temperature:
This setpoint defines the step value by which the
Pulldown Setpoint will decrease in each step when the
Pulldown Operation is running.
Figure 5-15. Compressor Control Screen – Pulldown Control
MicroVission Controller • Operation and Service Manual • Emerson • 35391MV 1.3
(Active Control Mode – Process Control SP1)
Delay Per Step:
This setpoint defines the time interval between each
pulldown step, i.e. Pulldown Setpoint will decrease after
the Delay Per Step time is elapsed when the Pulldown
Operation is running.
Stop Pressure / Temperature:
This Setpoint defines the value till which the Pulldown
Setpoint will decrease, i.e. when the Pulldown Operation
is running, The Pulldown Setpoint will stop decreasing
once the Pulldown Setpoint reaches this setpoint value.
Auto Cycle Differential Start Pressure / Temperature
Offset:
This Setpoint defines the value which will be added as
an offset in Pulldown Setpoint to calculate the value of
Pulldown Auto Cycle Start Pressure/Temperature which
will be used to start the compressor by auto cycle when
Pulldown Operation is running.
Auto Cycle Differential Stop Pressure / Temperature
Offset:
This Setpoint defines the value which will be subtracted
as an offset from Pulldown Setpoint to calculate the val-
ue of Pulldown Auto Cycle Stop Pressure/Temperature
which will be used to stop the compressor by auto cycle
when Pulldown Operation is running.
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