GEA Grasso - Setting the Setpoint; Limit Values and Safety Devices; Switching on the CO Refrigerant Pumps; Switching on the Compressor; Checking the Adjustment of the Control Slide

OPERATING INSTRUCTIONS
CO
2
/NH
3
CASCADE UNIT
250 - 1000 KW
20 _551511_om_kas_gbr_1_.doc
3. The maximum end position (100%) must be
reached and signalled on operating pushbutton
switch (capacity increasing).
1.6.2.12 Setting the setpoint / limit values and
safety devices
The setpoint and limit values are set according to the
details given in the Control Manual and the project-
related data.
4. The minimum end position (0%) must be
reached and signalled on operating pushbutton
switch (capacity decreasing).
Check the safety device settings.
5. Vent the adjusting device by moving the control
slide to and for about ten times.
Hint!
See parameter list/ list of set values!
1.6.2.16 Checking the control slide adjustment times
While the cascade is running, determine the
adjustment times needed when the control slide is
continually moved from the maximum end position
to the minimum end position and back. For the
automatic system to run smoothly, the adjustment
times in either direction must be approximately the
same.
refrigerant pumps
1.6.2.13 Switching on the CO
2
refrigerant pump ON" pushbutton
Press the "CO
2
1.6.2.14 Switching on the compressor
Start NH
compressor
3
Minimum adjustment time 30 sec.
Press the "Compressor ON" button
The following switching operations are automatically
realised with the compressor startup:
Optimum adjustment time 60 sec.
— Oil-fired heating switched off.
The adjustment times are matched by means of
throttle screws mounted on the solenoid valve plate.
— "Oil pressure bypass" timer starts up.
— Minimum output level after reduced-load startup
While the compressor is starting up the following
readings are to be observed on the cascade:
— Suction pressure, final compression pressure and
oil pressure
— Heat transfer medium temperature
— Sign glasses in the evaporator or in the liquid line
and compressor's housing
compressor
Start CO
2
The switching operations are analogous to those of
the NH
3
compressor.
The "Increase output" and "Reduce output"
pushbuttons can be used to reach the project values
and run the cascade in steady state condition.
fig. 20: Solenoid valve plate with throttle screws
The NH
3
and CO
2
compressor output levels should be
alternately switched on and off so that, as far as
possible, both run under the same load.
adjustment time ↓
Rotate in clockwise direction
adjustment time ↑
Rotate in anti-clockwise direction
The refrigerant charge must be checked and
recharged if necessary!
Influencing towards Maximum DS5
1.6.2.15 Checking the adjustment of the control
slide
Influencing towards Minimum DS6
1. Cascade is running.
2. Select operating mode ”1 (manual + manual)”.