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4. Design and functioning
25
Stopping the system
•
To de-energise the solenoid valves (- 19 - (Y1) and
- 20 - (Y4)) press the OFF push-button on the
keypad of the compressor control GD Pilot MK.
•
The pressure control valve (- 2.2 -) in the intake
regulator (- 2 -) closes and the pressure reservoir is
unloaded to atmospheric pressure.
•
After 30 seconds, the drive motor (- 3 -) and the
cooling air ventilator motor (- 26 -) are shut down.
Automatic operation (open-close operation)
•
When the pressure reaches the upper switching
point set on the network pressure sensor (-28 -
(B1)), solenoid valves (- 19 -(Y1) and - 20 - (Y4))
are deenergised.
•
The pressure control valve (- 2.2 -) closes.
•
This occurs because the lower control area of the
operating cylinder (-2.1-) is charged with pressure
by the current-free switched valve (-19- Y1), and the
upper control area is bled via the solenoid valve
(-20- Y4).
•
The oil separator vessel (-6-) is released to the idle
pressure (residual pressure).
•
The screw compressor is now running in the offload
mode.
•
The cooling air ventilator (- 26 -) is switched on or
off in dependence upon the final compression
temperature.
•
When the pressure at the network pressure sensor
(- 28 - (B1)) does not fall to the set lower switching
point within the set motor run-on time (e.g. 120
seconds), the drive motor (- 3 -) and the cooling air
ventilator motor (- 26 -) are shut down and the
system is depressurised to atmospheric pressure.
•
The system is now in the “stand-by” mode and can
restart at any time when the network pressure falls
to the lower switching point (see section “Starting of
the system”).
•
When the pressure at the network pressure sensor
(- 28 - (B1) falls to the preset lower switching point
before the set motor run-on time has elapsed,
solenoid valves (- 19 - (Y1) and - 20 - (Y4) ) are
again energised.
•
The unit now changes over to on-load operation.