OPERATING INSTRUCTIONS
GRASSO SYSTEM CONTROL
FOR TWO STAGE CHILLER/ PACKAGES WITH SCREW
COMPRESSORS
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The operating status provides information about the compressor unit.
The following status messages are possible:
Initialisation
Initialisation of the control after switching on the power supply or after saving the
settings (RAM
→
ROM)
Start to start HP
A switch on frequency limitation of the HP compressor drive motor is still active
Oil drain
A switch on block period is active, the oil pump has run too long by itself
(Minimum position was not reached during start or stop procedure)
Standby
Compressor unit/ chiller ready for switching on, but one or more starting conditions
are still not fulfilled e.g. process variable still below set point
No start release
The controller is waiting for an external signal to enable the start of the unit
Force to Min HP
Starting procedure issued, slide moves to minimum position (HP)
Starting HP
Compressor motor has been started, but the switchover to "Delta" has not yet taken
place or the startup has not yet been completed.
Running
Compressor motor running in "Delta" or startup has been completed. Package/ Chiller
in operation.
Psuc Limitation
A capacity limitation is active (suction pressure too low), "reduce output" solenoid
valve is opened.
Pdis Limitation
A capacity limitation is active (discharge pressure too high), "reduce output" solenoid
valve is opened.
Imot Limitation HP
A capacity limitation is active (HP motor current too high), "reduce output" solenoid
valve is opened.
Text Limitation
A capacity limitation is active (external temperature too low), "reduce output"
solenoid valve is opened.
Toil Limitation
Oil temperature too high, "refrigerant injection" is enabled (optional)
Stopping HP
The compressor unit/ chiller has received a shutdown command, the capacity slide is
moved towards its minimum position (HP)
Compressor off
The compressor has switched off
Stop to start timer
Start delay after each stop
Failure
A failure has occurred, which is still active.
Pump by itself
The minimum position was not reached during switch on or off procedure. The oil
pump continues to try to adjust the control slide in the min direction. After the oil
pump run by itself the oil block period becomes active.
Pull down Pinterm
The intermediate pressure is drawn off down to the switch on pressure (release of
the LP compressor)
