Sab 120 And 151 Without Oil Pump - Johnson Controls SABROE UniSAB III Engineering Manual

Compressor control and surveillance
3.3.17

SAB 120 and 151 without oil pump

The compressors are equipped with capacity slide and automatic Vi-control. The Vi is controlled in three
steps. 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 capacity slide
is in minimum position. If the capacity slide is higher than 10% position, the solenoid valve for decreas-
ing capacity slide position will be activated for maximum 300 seconds. If the capacity slide is still higher
than 10% position, a Capacity error shutdown will be issued and the compressor will not start. If the ca-
pacity slide is lower than 10% position 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 is-
sued. 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:
Low oil pressure
High filter diff. pressure
Low superheat
High superheat
Low/high oil temperature
The delayed alarms are described in section 6.5 Timers.
Stopping sequence
When a SAB 120 and 151 compressor stops, UniSAB III will attempt to move the capacity slide below
10% position. The solenoid valve for decreasing capacity slide position is activated for maximum 300
seconds. If the capacity slide is not below 10% within the 300 seconds a Capacity error shutdown will be
issued.
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 can-
celled. The Vi-step stays in volume ratio 2.2 (0.0%) until the compressor capacity is higher than 40%.
Volume ratio 2.2
Volume ratio 3.5
Volume ratio 5.0
Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
45 sec.
600 sec.
300 sec.
300 sec.
300 sec.
Vi slide position
../Capacity/Vi slide
pos.
0.0 %
65.3 %
100.0 %
113/346
Dig. output 11 (V1)
On
Off
Off
Dig. output 12 (V2)
On
On
Off