GEA Grasso Manual page 43

Grasso
Refrigeration Division
2.5.3 Switching off sequence in the normal case and in case of an alarm with 'Pump down'
Stop command
Output — compressor motor on
Decrease of capacity
Minimum capacity reached
'Pump down' timer active
Stop pressure reached
Alarm generated
A Normal case:
is
B In case of an alarm:
•
If (1)
→
Then (3)
→
(5)
Then
•
(4)
If
and (6)
→
Then
or
•
If (4)
and (5)
→
(7)
Then
→
Then
01.2004/1
Figure 2.8, Switching off sequence in the normal case (A) and in case of an alarm (B)
with ' Pump down'
As soon as the minimum capacity and the stop pressure are reached the
capacity control solenoids are de-energised and the compressor motor
stopped.
As soon as the 'Pump down' timer has expired the capacity control solenoids
are de-energised and the compressor motor is stopped.
Stop command
Decrease of capacity
'Pump down' timer active
Minimum capacity reached
Stop pressure reached
Reset the actuating signals (2) and (3)
Minimum capacity reached
'Pump down' timer expired
Generate alarm
Reset the actuating signals (2) and (3)
638660E_chapter2.doc
GRASSO SYSTEM CONTROL
Chap. 2 - 7