Alarm surveillance
During start the following alarms are delayed:
Low oil pressure 45 sec.
High filter diff. pressure 300 sec.
Low superheat 300 sec.
High superheat 300 sec.
Low/high oil temperature 300 sec.
The delayed alarms are described in section 6.5. Timers.
3.3.14 GST with oil pump
The compressors are equipped with capacity slide and automatic Vi-control. The Vi is control-
led in three steps.
The oil pump is used to maintain a minimum oil pressure level during operation and to return
the capacity 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.
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 at the lowest pressure level.
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.
Adjust Setpoint 2 the same way.
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 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. 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, 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.
If the differential pressure is higher than Set point 1 when the compressor is started, the oil
pump will not start.
Compressor control and surveillance
Engineering manual - Unisab III 1.10
001930 en 2014.09
103/319
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