Maintenance & Service; Propane Gas; Burner Features - Kärcher HDS3.5/20 Operator's Manual

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Adjustment of the built-in regulator isn't normally nec-
essary, since it is preset at the factory. However, fi eld
adjustment may be accomplished as follows:
1. Attach manometer at pressure tap port.
2. Remove regulator adjustment screw cap.
3. With a small screwdriver, rotate the adjustment
screw clockwise to increase or counterclockwise
to decrease gas pressure.
4. Replace regulator adjustment screw cap (see
Figure 5).
Figure 5
Gas Valve Regulator Adjustment
Lines To
Pilot Light
Manifold Pressure
Adjustment Screw
Under Cap
Pressure Relief Valve
Each machine is equipped with a relief valve to relieve
pressure in the system when higher than normal
operating pressures are encountered. If operating
pressure of machine is found to be normal and relief
valve continues to leak, repair or replace the valve.
CAUTION: Relief valve can become obstructed by
deposits and must be unscrewed at least once per
year to allow discharge.


General Safety Precautions
Have a qualifi ed gas service person assist in any gas
burner installation or service. Few maintenance people
or mechanics are knowledgeable in gas controls or
related safety practices. Propane gas is heavier than
air; unburned propane gas will gravitate to the fl oor
rather than rise out of the stack. Hence, adequate fl oor
space and good ventilation are especially important
with propane systems.
Gas Valve
Inlet View
9.801-509.0 - C • Karcher Operator's Manual
Gas Pressure Requirements
All propane fi red machines operate on vapor propane
fuel only. They are designed to operate at a pressure of
11 w.c.i. (between 1/3 and 1/2 of one psi), and are
often operated at even higher pressures when extra
heat is needed.
Exterior regulators are needed to control gas pressure.
Propane bottles are not included with the machine. A
pressure regulator should be installed between pro-
pane bottle and gas valve.
Propane Cylinder Capacity
An important consideration with propane systems is
the capacity of the supply cylinder relative to the needs
of the burner. The burner operates on propane as a
vapor gas. As gas is used from the propane cylinder,
the liquid in the cylinder boils to maintain vapor gas
pressure. This boiling process cools the liquid, and in
a heavy, continuous-demand situation, the liquid tem-
perature can fall to the point at which it cannot provide
vapor gas as rapidly as is needed. In this case, it may
be necessary to warm the propane cylinder by direct-
ing a warm spray, not over 120°F, on the cold cylinder
or by manifolding two propane bottles together to in-
crease total vaporization capacity. It is recommended
that a minimum 100 lb. vapor propane bottle be used
on the machine, depending on the length of running
time desired.


Operated Automatic Valve
This machine is equipped with an Intermittent Pilot
Ignition System. This system is designed to eliminate
the need for a constant burning pilot. Lighting of the
pilot is accomplished through electronic spark ignition
each time the burner switch is turned on. Do not at-
tempt to light the appliance manually as a burn injury
or electrical shock may result. The pilot light will remain
on and the main gas valve is turned off when the spray
gun is closed.
Care of Main Burner
Due to condensation from heater coils dripping down
on the burners, scale build-up may occur in the burner
jet orifi ces.
Turn off the gas to the main burner by turning the
knob to the "OFF" position on the gas valve and
the main gas supply.
Disconnect the pilot and ignition lines from the gas
valve. Disconnect union in main burner line below
thermostat. Slide burner manifold out through shell


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