HDS Middle Range / HDS Premium Range
Unit Function
Service Manual 04.2008
Page 61 / 127
1 High-pressure outlet, switch-off pressure
2 Pressure gauge, switch-off pressure
3 Non-return valve (closed)
4 Rotary knob
5 Overflow valve (open)
6 Throttle bore
7 Pressure switch, „OFF“ (open)
8 Water inlet
9 Motor protection contacts (K1) (open)
10 Pump is at a standstill
11 Pressure switch, „ON“ (open)
2.27.3 Handgun is closed
When the handgun is closed a short-term
overpressure occurs in the system. This causes
the overflow valve (5) to open and the whole
delivery volume flows through the throttle bore
(6) into the suction chamber of the pump.
As soon as the overflow valve (5) opens, the
non-return valve (3) closes and the switch-off
pressure is enclosed between the handgun and
non-return valve (3). The enclosed switch-off
pressure causes the pressure switch (11) to
remain open.
At the same time, a back-pressure results in the
throttle bore (6), which opens the pressure switch
(7) at approx. 10 bar and this interrupts the control
circuit. The motor protection contacts (9) open
and the motor are switched off.
As soon as the motor is at a standstill, the overflow
valve (5) and the pressure switch (7) closes.
The motor protection contacts (9) continue to
remain open however, as the control circuit is
only interrupted by the opened pressure switch
(11) (see circuit diagram).
1
2
3
4
5
6
7
8
10
11
9
24 volt
2.27 Pressure switch function