Johnson Controls SABROE Unisab III Control, Engineering Manual

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Engineering manual - UniSAB III 1.10.8
001930 en 2021.06
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Alarms and shutdowns
Note that in version 1.10.7, this shutdown also covers SAB 193 H, 233 H, 283 H and 355 H.
2.2.31 Insufficient main oil pressure alarm
SGC compressors (SAB 157 HR)
This alarm is released if the oil pressure is < [1.5 x P
suct
] + 1 bar. The alarm delay is 180 seconds. When
the main oil pressure is too low, the limiting function Insufficient main oil pressure (SAB 157 HR) will un-
load the plug valve, with no delay. See Fig. 9 and subsection 3.2.3 Special limiters .
The main oil pressure is calculated as main oil pressure = P
oil, abs
- 1.50 x P
suction, abs
.
2.2.32 Insufficient main oil pressure shutdown
SGC compressors (SAB 193 H → → 355 H and SAB 273 S)
This shutdown is released if the main oil pressure < 1.0 bar and at the same time the capacity slide is
above 50%. The shutdown delay is 180 seconds. When the oil pressure is too low, this function limits ca-
pacity to max. 50% and the capacity cannot increase if it is between 40 and 50%. For screws with both
capacity slide and frequency converter, the limitation only affects the capacity slide, not the VSD. See
Fig. 8.
The calculation of main oil pressure depends on whether the economiser function is disabled or
enabled:
If the economiser function is disabled, main oil pressure = P
oil, abs
- 1.50 x P
suction, abs
.
If the economiser function is enabled, main oil pressure = P
oil, abs
- 1.75 x P
suction, abs
.
To avoid capacity and Vi slide fluctuations due to economiser engagement/disengagement, the shift be-
tween the two main oil pressure factors, 1.50 and 1.75, is made with a hysteresis.
2.2.33 Low oil circuit pressure alarm
SGC compressors (SAB 120 → → 151, SAB 193 → → 355, SAB 193 H → → 355 H, SAB 157 HR, SAB 273 S and
SABflex)
This alarm is issued if the pressure difference between discharge pressure minus oil pressure exceeds
2.7 bar. The alarm delay is 600 seconds. See Fig. 10.
2.2.34 Low oil circuit pressure shutdown
SGC compressors ( SAB 120 → → 151, SAB 193 → → 355, SAB 193 H → → 355 H, SAB 157 HR, SAB 273 S and
SABflex)
This shutdown is issued if the pressure difference between discharge pressure minus oil pressure ex-
ceeds 3.0 bar. The shutdown delay is 900 seconds. See Fig. 11.
2.2.35 Critical oil circuit pressure shutdown
SGC compressors (SAB 120 → → 151, SAB 193 → → 355, SAB 193 H → → 355 H, SAB 157 HR, SAB 273 S and
SABflex)
This shutdown is issued if the pressure difference between discharge pressure minus oil pressure ex-
ceeds 5.0 bar. The shutdown delay is 25 seconds. See Fig. 12.
2.2.36 Oil pump low pressure alarm
SGC compressors (SAB 120 → → 151, SAB 193 → → 355, SAB 193 H → → 355 H, SAB 157 HR and SAB 273 S)
This alarm is issued if the oil pump excess pressure is less than a preset value, see Table 9. The alarm
is only active when the oil pump is running, and it is delayed with a preset delay
Oil pump low alarm , see
Table 52.
For SAB 120
→ 151, SAB 193 → 355, SAB 193 H → 355 H, SAB 157 HR and SAB 273 S, the oil pump