Guardian SCC 25, Manual

Page: 34 / 79

Page 34
GUARDIAN SCC-40 Issue (Auto VI) & V3.6t 07/12/00
SETPOINTS
SUCTION PRESSURE SETPOINT CONTROL.
-0.5 to 5.0bar
the suction pressure control setpoint for the compressor in increments of 0.1 bar.
If ‘CHIL’ is selected then loading is inhibited until the suction is above this
setpoint.
EQUIVALENT TEMPERATURE SETPOINT (tcon)
-50 to 50
°
C
the equivalent temperature control setpoint of the compressor in increments
of1
°
C. This setpoint can be switched between two values using input
H (high setpoint if on).
WATER CHILLER TEMPERATURE SETPOINT (CHIL)
-1 to 24
°
C
the water chiller temperature RT5 control setpoint of the compressor in
increments of 0.1
°
C.
SETPOINT CONTROL
Capacity loading takes place when the control temperature or suction pressure
is greater than the setpoint.
Capacity unloading takes place when the temperature or suction pressureis less
the setpoint.
When the suction pressure is (0.3 bar, 0.3
°
C,3
°
C) above or below the setpoint
then the width of the load and unload pulses is automatically doubled and
pulses are sent every five seconds to achieve suction setpoint more rapidly.
When the setpoint is within 0.3 of the setpoint then the loading valves are
pulsed at the variable CAPACITY LOAD DELAY period to give time for plant to
respond before sending the next pulse which prevents 'hunting'.
When the slide capacity is below 75%, loading pulses are doubled to
counteract the effect of a non linear slide travel.
DISCHARGE TEMPERATURE SETPOINT
Liquid Injection ON . setpoint is the discharge temperature above which the
liquid injection valve is opened. The liquid injection valve is shut when the
temperature falls 5 degrees C below this setpoint.
Filter differential high alarms are inhibited until this setpoint is reached in order
to ensure reasonable oil flow.
LIQUID INJECTION 2 IF 'Bypass' valve is selected then a second injection valve
connected to VI-1 output is switched on 5
°
C above the discharge temperature
setpoint and switched off at the setpoint
DISCHARGE DIFFERENTIAL SETPOINT
STOP PUMP
When 'P-St' is selected, this is the differential discharge to suction pressure
above which the pump is stopped if it is only required during compressor startup.