Kärcher HPB Series Operator's Manual page 19

Burner Nozzle:
Keep the tip free of surface deposits by wiping it with a
clean, solvent-saturated cloth, being careful not to plug
or enlarge the nozzle. For maximum efficiency, replace
the nozzle each season.
Fuel Control System:
This machine utilizes a fuel solenoid valve located on
the fuel pump to control the flow of fuel to the combus-
tion chamber. This solenoid is activated by a pressure
switch located on the unloader valve. When an
operator releases the trigger on the spray gun, the
pressure drops, allowing the pressure switch to activate
the fuel solenoid. The solenoid then closes, shutting off
the supply of fuel to the combustion chamber.
Controlling the flow of fuel in this way gives an instanta-
neous burn or no burn situation, thereby eliminating
high and low water temperatures, and combustion
smoke normally associated with machines incorpo-
rating a spray gun. Periodic inspection is recom-
mended to insure that the fuel solenoid valve functions
properly. This can be done by operating the machine
and checking to see that when the trigger on the spray
gun is in the off position, the burner is not firing.
Fuel Pressure Adjustment:
To adjust fuel pressure, First install a pressure gage
into the port just after the pump fuel exit. Turn the
adjusting screw (located at the regulator port)
clockwise to increase, and counterclockwise to
decrease. Do not exceed 200 psi or lower the pressure
below 130 PSI, when checked at the post-pump
pressure port.
The fuel pressure may need to be adjusted due to
altitude. For every 500 ft altitude above sea level, the
boiling point of water goes down 1 °F. At high altitude
environments, this boiling point change may require the
heat input to be lowered so the water input does not
turn to steam earlier than at the factory settings and
activate the pressure sensors and pressure relief
equipment when the unit is operated and much higher
altitudes from factory settings or local dealer site
settings. Check with your dealer before making local
site fuel pressure adjustments.
Also, as ambient temperature changes seasonally, the
fuel temperature in the feed tank and air temperature
inlet can impact fuel flow. In more extreme tempera-
tures, this local-site adjustment may also require
different fuel nozzles for fuel inlet temperatures that are
at seasonal extremes (higher or lower) in locations
where the temperature changes are beyond moderate
Kärcher HPB Series Operator's Manual 9.801-190.0 - W
temperatures of between 40°F and 90°F. Colder
temperatures will make for a thicker flow and less fine a
fuel spray while hotter temperatures will make for a
thinner flow a more fine spray with the same nozzle.
Consider alternate nozzle configurations from the
baseline factory-supplied nozzle for operating in such
temperature extremes if performance is not meeting
needs with air band and fuel pressure settings alone.
NOTE: When changing fuel pump, a by-pass plug
must be installed in return line port or fuel pump will
not prime
Air Adjustment
The oil burner on this machine is preset for operation at
altitudes below 500 feet. If operated at higher altitudes,
it may be necessary to adjust the air band for a #1 or #2
smoke spot on the Bacharach scale.
To adjust, start machine and turn burner ON. Loosen
two locking screws found on the air band and close air
band until black smoke appears from burner exhaust
vent. Note air band position. Next, slowly open the air
band until white smoke just starts to appear. Turn air
band halfway back to the previously noted position.
Tighten locking screws.
For higher altitudes, the air band opening may need to
be increased; for lower altitude, the air band may need
to be decreased.
For higher humidity, the air band opening may need to
be increased; for lower relative humidity, the air band
may need to be decreased.
For higher ambient temperatures the air band opening
may need to be increased; for lower ambient tempera-
tures, the air band opening may need to be decreased.
Adjust to your operating location's environment as-
needed for best smoke spot and performance
compliant with local, state, and federal regulations.
To adjust: start machine and turn burner ON. Loosen
the two locking screws found on the air band openings
(refer to illustrations) and close air band until black
smoke appears from burner exhaust vent. Note air
band position. Next, slowly open the air band until white
smoke just starts to appear. Turn air band halfway back
to the black smoke position previously noted. Tighten
locking screws.
Maintenance
19