Kärcher HDS Middle series Service Manual page 47

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HDS Middle Range / HDS Premium Range
2.19 Continuous-flow heater
1 Ignition electrodes
2 Fuel nozzle
3 Boiler base
4 Boiler inlet
5 Air supply from burner fan
6 Boiler jacket, double-walled
7 Heating coil winding, external
8 Heating coil winding, internal
9 Exhaust connecting sleeve
Service Manual 04.2008
The water from the high-pressure pump enters
the internal heating coil winding (8) from
underneath, is heated as it flows through and
exits downwards again from the external heating
coil winding (7).
The fuel is atomised by the fuel nozzle (2) and is
ignited by the ignition sparks of the ignition
electrodes (1).
The combustion air from the fan (5) first flows
from underneath and upwards through the
double-walled boiler jacket (6), then downwards
with the flame and passes up through the exhaust
gas flue (9) into the open air as exhaust.
The boiler base (3) is made from fire-resistant
insulating cement. It prevents radiation of the
heat and helps to divert the flames.
The burner is adjusted to good emission values
using the air flap on the fan (air volume) and
using the adjusting screw on the fuel pump (fuel
pressure).
The temperature increase at full water volume is
approx. 60-65 °C. If the water volume is reduced
by the pressure and flow control valve, the water
can be heated to approx. 100 °C; if the steam
nozzle is used it can be heated up to 155 °C*.
Optimum burner performance is only possible if
the heating coil is neither sooted up nor are there
any internal deposits. In addition, the ignition
electrodes, the fuel volume and the air volume
must be correctly set.
Steam operation
The following preparations have to be made for
steam operation:
– Install the steam nozzle
– Adjust operating pressure at the pump's
pressure and flow control valve to the smallest
value.
– Set the required steam temperature at the
control panel.
* Note on steam operation
According to the Pressure Equipment
Directive, the operating pressure in the unit
must be less than 32 bar for steam operation.
This is ensured by reducing the operating
pressure at the pressure and flow control
valve and using the steam nozzle supplied.
Unit Function
Page 47 / 127

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