If the differential pressure is higher than Set point 1 when the compressor is started, the oil
pump will not start.
Alarm surveillance
During start the following alarms are delayed:
Low oil pressure 45 sec.
High filter diff. pressure 600 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.
Stopping sequence
When a SAB 193-233-283-355 compressor stops, Unisab III will attempt to move the capacity
slide below 5% position. The solenoid valves for decreasing capacity and Vi position are acti-
vated for maximum 300 seconds. If the capacity slide is not below 5% within the 300 seconds
a Capacity error shutdown will be issued.
Balance piston for SAB 355
For SAB 355, the AUX output is dedicated for control of the balance piston. Choose the AUX
output to be activated At max. cap. in the menu Compressor control – user functions and set
the Signal high limit to 70% referring to slide capacity.
3.3.19 SAB 193, 233, 283 and 355 without 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 compressor has no oil pump.
Starting sequence
When the compressor has received starting permission, Unisab III will check whether the ca-
pacity slide is in minimum position. If the capacity slide is higher than 5% position, the sole-
noid valve for decreasing capacity slide position will be activated for maximum 300 seconds.
If the capacity slide is still higher than 5% position, a Capacity error shutdown will be issued
and the compressor will not start. If the capacity slide is lower than 5% position the compres-
sor 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 tempera-
ture 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.
Alarm surveillance
During start the following alarms are delayed:
Compressor control and surveillance
Engineering manual - Unisab III 1.10
001930 en 2014.09
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