Engineering manual - UniSAB III 1.10.8
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001930 en 2021.06
Compressor control and surveillance
3.3.18 SAB 193, 233, 283 and 355 with oil pump
The compressors are equipped with capacity slide and automatic Vi-control.
If the compressor is equipped with a frequency converter (VSD) see subsection 6.4.1 Drive, 6: Rotatune
for additional set-up of UniSAB III.
The pump is used for maintaining a minimum oil pressure level during operation and for returning the ca-
pacity slide to minimum position before the compressor is started. During operation the oil pump is
started and stopped in accordance with the compressor differential pressure (discharge pressure - suc-
tion pressure).
The difference is set in the picture Oil/Pressure/Control whereupon Set point 1 and Set point 2 will
appear.
Set point 1 is the pump start pressure and Set point 2 is the pump stop pressure. Therefore, Set point 1
must be set for the lowest pressure level.
Adjust Set point 2 the same way.
Normal setting for SAB 193-233-283-355
Set point 1 = 2.5 bar.
Set point 2 = 3.0 bar.
Move the cursor to Set point 1, press to enter the parameter change field, use and to adjust the
value and press to store the value.
If the compressor differential pressure is below Set point 1 during operation, the pump will start
immediately.
When the compressor differential pressure has been higher than Set point 2 for 60 seconds, the pump
will stop.
Starting sequence
When the compressor has received starting permission, UniSAB III will check if the capacity slide is in
minimum position. If the capacity slide is higher than 5% position, the oil pump is started for maximum
30 seconds and the solenoid valve for decreasing the capacity slide position is activated. If the capacity
slide is still higher than 5% position, an Oil log error shutdown will be issued and the compressor will not
start. If the capacity slide is lower than 5% the compressor is allowed to start.
Before start-up UniSAB III will also check the oil level and temperature in the oil separator. If the oil level
is too low an oil system error alarm will be issued. No signal from the oil level switch during operation will
result in shutdown after a delay of 30 seconds.
If the oil temperature is lower than the set limits a low oil separator temp alarm or shutdown will be is-
sued. The limits for oil separator temperature can be set in the menu Control values/Oil/Separator temp/
Limits.
If the oil level switch is active and the separator temperature is above the shutdown limit, the compressor
will start. If the differential pressure is lower than Set point 1, the oil pump will also start. When the com-
pressor differential pressure has been higher than Set point 2 for 60 seconds, the pump will stop.
If the differential pressure is higher than Set point 1 when the compressor is started, the oil pump will not
start.
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