RWF II ROTARY SCREW COMPRESSOR UNITS
OPERATION
070.610-IOM (JUN 11)
Page 19
Figure 21 - PID Setup
Figure 22
OPERATION OF DANFOSS
LIQUID INJECTION VALVE
ICAD (Industrial Control Actuator with Display) is equipped
with an MMI (Man Machine Interface) from which it is possible
to monitor and change the setting of parameters to adapt
the ICAD and the corresponding ICM (Motorized Industrial
Control Valve) to the actual refrigeration application.
The setting of parameters is managed by means of the
integrated ICAD MMI (Figures 22 and 23) and consists of:
NOTES:
1. Set the “Liquid Slugging” Alarm and Shutdown setpoints
to 90 to prevent nuisance shutdowns during the tuning
process. Be sure to return these setpoints to their original
values when nished.
2. While the discharge temperature will be the Control Point,
it reacts quickly to adjustments. Be sure to allow an adjust
ment to the proportional band or integral gain setpoints the
opportunity to counter and correct the control input (dis
charge temperature) before making additional adjustments.
3. Tune the output by making small adjustments of 15 to
the Proportional Band and .1.5 of the Integral Gain setpoints.
Adjust only one at a time, allowing each adjustment time to
settle out.
• Using the chart below, as long as the control input
is 155°F the output will be at 20% with proportional
control only. Integral control will increase the output
in increments, over time, to correct the control input
to the setpoint.
Control Input Output %
150°F 0%
155°F 20%
160°F 40%
165°F 60%
170°F 80%
175°F 100%
Based on these descriptions set PID #1 for EZ-Cool
™
LIOC
per Figure 21 as a starting point. Tuning of the output will be
required. There should be no need to use a derivative gain.
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