Vi slide position
../Capacity/Vi slide
pos.
Dig. output 11 (V1) Dig. output 12 (V2)
Volume ratio 2.2 0.0 % On On
Volume ratio 3.5 65.3 % Off On
Volume ratio 5.0 100.0 % Off Off
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 re-
turning the capacity slide to minimum position before the compressor is started. During oper-
ation the oil pump is started and stopped in accordance with the compressor differential pres-
sure (discharge pressure - suction 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 po-
sition is activated. If the capacity slide is still higher than 5% position, an Oil log error shut-
down 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 issued. 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 compressor differential pressure has been higher than Set point 2 for 60
seconds, the pump will stop.
Compressor control and surveillance
108/319
Engineering manual - Unisab III 1.10
001930 en 2014.09
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