Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
117/346
Compressor control and surveillance
Alarm surveillance
During start the following alarms are delayed:
Low oil pressure 15 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.
Running
After the starting sequence and during normal running operation the following SSSTV limiters will be ac-
tive: high torque, low oil pressure and high internal suction pressure. See subsection 3.2.3 Special limit-
ers for more information.
Stopping sequence
At normal stop (to avoid back-spin) the SSSTV valve is closed for the time stated in the timer SSSTV de-
lay before the compressor is stopped. The default setting is 40 seconds but it is adjustable between 0
and 60 seconds.
Note: The SSSTV timer starts counting after the stop delay timer has run out. This means that the com-
pressor will not stop immediately even though the stop key is pressed or the instant stop digital input is
removed.
After compressor stop the SSSTV valve is kept closed for 60 seconds, not adjustable, and the internal
water cooling pump will have a stop delay of 60 seconds.
At shutdown the frequency converter is stopped immediately and the SSSTV valve is closed
immediately.
Vi ratio regulation
UniSAB III regulates the Vi ratio in three steps according to the actual pressure ratio. Before switching
from one Vi step to another, the actual Vi ratio for the compressor must have been present for at least
the time indicated in timer 34 Vi-pause (60 seconds). Otherwise the change of the Vi step will be
cancelled.
Vi ratio .../Capacity/Vi ratio
Vi low range setting Vi high range setting
Dig. output 12 (Vi)
1.9 2.6
Off
3.2 4.8
On
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