2.2. Other alarms and shutdowns
2.2.1 High oil differential pressure (SMC Mk4)
The alarm is delayed 300 seconds during start. It is released if the oil filter differential pres-
sure becomes too high.
2.2.2 Oil system error (screw compressors)
The reason for the shutdown is either that the oil flow switch is not activated within the time
set in the timer Oil flow during prelubrication or that there is a drop-out on the oil flow switch
for a longer period than the one set in the timer No oil during operation.
For SAB 80/GSV-RWF/SAB 120-151, SAB 157HR, SABflex and SAB 193-233-283-355, this is
an oil separator level shutdown.
For SAB 109-159 this is an oil separator level shutdown.
2.2.3 Capacity error (screw compressors)
This shutdown/alarm is not active for SABflex and SABCube compressors
(SAB109→159)
The reason for the shutdown is one of the following:
• The capacity slide is not below 5% within the time set in the timer Slide max. at com-
pressor stop.
• During operation, the slide has not moved within 30 minutes, although the regulator
should regulate up or down and the output signal from the regulator is above 20%.
• In connection with automatic setting of variable zero point, the slide cannot reach the
position corresponding to calculated or adjusted zero point (i.e. positive read capaci-
ty) before the expiry of the timer Capacity negative.
Additional description
1. If the compressor is in operation and set at Manual or Auto and the slide does not re-
act to the regulating signal within 30 minutes, an alarm will be issued. The compres-
sor does not stop.
2. If the compressor is in operation and set at Remote and the slide does not react to
the regulating signal within 30 minutes, a shutdown will be issued. The compressor
will stop.
3. If the compressor is remote controlled by a PC/PLC-system, an alarm will be issued as
well. Monitoring is possible by means of a 4-20 mA signal in the aux. input or via
communication.
The reason for the difference between situation 1) and 2) is: If the system runs in sequence -
Remote (Multisab), the compressor must be stopped in order to start any subsequent com-
pressors in the sequence.
When a compressor is remote controlled (3) it is not a part of the sequence, remote (Multi-
sab) system. Thus stopping this compressor will not start up subsequent compressors.
2.2.4 PMS error
When Unisab III wants to start the compressor, the Start request (PMS) output is set at ON.
The input Start request OK must then be set at ON within the time set in the timer PMS feed-
back. If not, the shutdown will be activated.
Alarms and shutdowns
48/319
Engineering manual - Unisab III 1.10
001930 en 2014.09
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