Johnson Controls SABROE Unisab III Control, Engineering Manual

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Engineering manual - UniSAB III 1.10.8
60/346
001930 en 2021.06
Alarms and shutdowns
2.2.49 VSD backspin
SABflex and SABCube (SAB 109 → → 159) compressors
For SABflex and SABCube with Danfoss drive, this shutdown indicates that the discharge pressure after
compressor stop and after the timer
Backspin delay has run out is higher than the Internal suction
pressure .
For SABCube, this shutdown indicates that the drive during the compressor stop sequence is rotating
backwards with a speed of more than 5,000 rpm.
The shutdown will activate the POV valve to avoid the risk of backspin, i.e. that the compressor starts ro-
tating backwards. This might be caused because the SSTV valve did not close correctly at compressor
stop.
2.2.50 Network connection to VSD alarm
Compressors with VSD and Modbus drive communication
This alarm (“VSD link missing”) indicates that the Modbus communication between UniSAB III and the
VSD drive has been shortly disrupted, for 5 seconds.
2.2.51 Network connection to VSD shutdown
Compressors with VSD and Modbus drive communication
This shutdown (“Drive link error”) indicates that the Modbus communication between UniSAB III and the
VSD drive has been disrupted for 10 seconds, and that the drive for security reasons therefore has been
stopped. When UniSAB III goes into shutdown, the POV valve is closed.
To secure that the drive too is stopped in case of communication error, the drive is set up to stop the mo-
tor after 8 seconds.
The Danfoss drive must be set up as follows: 08-03 “Control word time out” set to 8 seconds and 08-04
“Control word time out function” set to 5 “Stop and trip”.
The Leroy Somer drive must be set up as follows: "Serial link monitoring" set to Yes , "Monitoring period"
set to 8 seconds and "Serial link fault" set to Major fault .
2.2.52 General drive error
Compressors with VSD and Modbus drive communication
This shutdown indicates that there is one or more faults in the Danfoss or Leroy Somer VSD drives. The
fault reason can be found in VSD menu no. 16-9 for the Danfoss drive and in menu no. 18 for the Leroy
Somer drive.
2.2.53 Forced speed alarm
SGC compressors (SAB 120 → 151, SAB 193 → 355, SAB 193 H → 355 H, SAB 157 HR and SAB 273 S)
For these screw compressor types with frequency converter this alarm indicates that the speed is forced
up during the start-up phase. In this “forced speed” phase the frequency converter will regulate up to a
predefined speed and stay there as long as the main oil pressure is low. When the main oil pressure is
above its minimum limit this alarm is automatically reset.
2.2.54 Oil pressure diagrams
In the following diagrams, the absolute oil pressure (P
oil
) is the oil pressure displayed in the oil p
the suction pr 1 bar (atmosphere). The absolute suction pressure (P
suct
) is the displayed suction
pr 1 bar (atmosphere).