GEA Grasso - Page 43

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