Kärcher HDS 7/12 M, Service Manual

Page: 67 / 131

English 5.906-432.0 Rev. 00 (06/15)
67
1 High pressure outlet, shut-off pressure
2 Manometer, shut-off pressure
3 Pressure retaining valve (closed)
4 Pump stands still
5 Rotary knob
6 Overflow valve
7 Reduction bore
8 Pressure switch "OFF" (open)
9 Water inlet
10 Motor contactors (K1) (open)
11 Pressure switch "ON" (open)
Note
The shown functions of the preessure switches and motor
contactor are for understanding purposes only.
In reality, the information from the two pressure switches is
transferred directly to the control electronics, which in turn
controls the motor contactor.
There will be brief overpressure in the system when the
gun is closed.
This will open the overflow valve and the entire flow vol-
ume streams into the suction chamber of the pump
through the throttle bore.
As soon as the overflow valve opens, the pressure retain-
ing valve closes and the shut-off pressure is locked be-
tween the gun and the pressure retaining valve.
Due to the locked in switch-off pressure, the pressure
switch "ON" remains open.
There will be a pressure backup in front of the reduction
bore, which opens the pressure switch "OFF" at about 10
bar and thus interrupts the control circuit.
The motor contactors open and the motor is shut off.
As soon as the motor has stopped, the overflow valve will
close and so will the pressure switch "OFF".
However, the motor contactors will remain open as the
control circuit is still interrupted by the open pressure
switches "ON".
6.32.3 Gun is closed
24 Volt
6
1 3 4
7
8
9
11
5
10
2