Engineering manual - UniSAB III 1.10.8
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001930 en 2021.06
Compressor control and surveillance
superheating of the plant must be entered as Set point 2 in the picture Control values/Suction/Super-
heat/Control if differing from the above factory value.
Adjusting range: -10 - +30°C
By adjusting Set point 2 for Suction superheat upwards or downwards, the limit curve will be dislocated
accordingly.
If Set point 2 is set at -10°C, the limit curve will be dislocated so much upwards that the limiting function
will be disabled.
Liquid level limiter (reciprocating compressors)
This capacity limiting function for ChillPAC Mk 3 works for all reciprocating compressors that do not use
the Filter diff. pressure function.
The limiter will reduce compressor capacity (3%/sec, up to 33-50%) as long as the liquid level is high in
the evaporator. When the liquid level is back to normal, and after the Liquid level delay has timed out,
the compressor is allowed to increase capacity.
Separator velocity (screw compressors)
For all screw compressors a capacity limiting function for high separator gas velocity can be activated. It
will limit the compressor capacity to a calculated limit based on the current running conditions. To acti-
vate the limiter, two values calculated from the Refrigeration Plant Computation program are required:
• Actual separator velocity limit reference
• The compression ratio at which the above value was calculated.
The high capacity limit for the separator is calculated by means of the measured compression ratio and
the two mentioned reference values. When the limiter inhibit function is active (i.e. capacity cannot be in-
creased) the text Running overload is shown in the status field on the display.
The Alarm picture reads: Limiting high separator flow. When the limiter force-unload function is active (i.
e. capacity will actively be decreased) the status text Running overload is shown in the status field on
the display.
The text in the Alarm picture reads: Limiting high separator flow.
The set up values for the limiter are entered in the Setup/Configuration/Oil system picture.
Min. Max.
Sep.vel.ref 0.49 0.00 10.00
Sep.vel.cr 4.72 0.00 100.00
The calculated (intermediate) values for the separator limiting function are shown in the Diagnosis pic-
ture Service/Diagnosis/Software/Separator Velocity.
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