Kärcher HDS 7/12 M Service Manual page 52

Mode of operation
The water from the high pressure pump enters the interior
heating coil spiral, is heated while flowing through and ex-
its to the bottom from the heating coil spiral.
The fuel is vaporised by the fuel nozzle and ignited by the
spark of the ignition electrodes.
The combustion air from the blower first flows through the
double-walled boiler exterior toward the top, then it flows
downward with the flame and is emitted as exhaust
through the exhaust stack toward the top into the atmos-
phere.
The boiler floor is made of fire-resistant insulating con-
crete. It prevents a radiation of the heat and is used to re-
route the flames.
The adjustment of the burner to good exhaust values is
achieved via the air flap on the blower (air volume) and
with the adjustment screw on the fuel pump (fuel pres-
sure).
The temperature increase with the full water volume is 60-
65 K independent of the device.
If the water volume is reduced via the pressure and volume
control, the water can be heated to approx. 100 °C; if you
use the steam nozzle, up to 155 °C.
An optimal burner performance is only possible if the heat-
ing coil is neither full of soot nor other deposits.
Furthermore, the spark electrodes, the amount of fuel and
the amount of air must be adjusted properly.
Steam operation
The following preparations must be made for steam oper-
ation:
Install steam nozzle
–
Set the operating pressure on the pressure and volume
–
control on the pump to the lowest value
Set the desired steam temperature at the operating
–
panel
Note
As per pressure device guidelines, the operating pressure
inside the appliance must be less than 32 bars for steam
operation.
This is ensured by reducing the operating pressure on the
pressure and volume control and by using the supplied
steam nozzle.
52
English 5.906-432.0 Rev. 00 (06/15)