two inches from combustibles. Vents passing through
enclosed spaces and vents exposed to the weather
should also be the double-wall type. Sometimes vents
have to be built of such great length that they come
apart at their joints under their own weight. These
should be screwed together at the joints with sheet
metal screws, usually three per joint. If the inspector
indicates that the vent is too close to combustibles, it
may be necessary to chisel away some of the com-
bustible or route the vent pipe around the combustible.
The cross-sectional area of any ﬂ ue shall not be less
that the cross-sectional area of the ﬂ ue vent connec-
tion outlet of machine.
Figure 3: Ventilation
Illustration showing air openings necessary
to supply air for combustion when installed
in an enclosed room.
The pressure washer includes a collar that will mate
with standard HVAC ducting. The user will be respon-
sible for installation of an exhaust stack. The exhaust
stack should include a Draft Diverter/Inducer, Damper,
Sampling Port and Rain Cap.
installed between the collar and stack to adjust the
diameter from 10" to 8" or 12" to 10".
Size the stack according to the following (see also
applicable local and national standards regarding
installation of gas-ﬁ red appliances):
3.5 to 4.4 gpm
4.5 to 5.5 gpm
8 – 10 gpm
Draft Diverter/Hood: The draft required to vent
combustion gases is created by the heat inside the
pressure washer coil. A draft diverter helps improve
draft into the stack without pulling more air through the
An adapter can be
9.801-509.0 - C • Karcher Operator's Manual
combustion box and decreasing combustion efﬁ ciency.
The draft diverter can also help prevent back drafting
that can inhibit combustion. The draft diverter should
be installed a minimum of 36" above the ﬂ ue collar.
See Figure 4.
Power Vent (Draft Inducer): If this machine is going
to be installed on a 90° or extended exhaust vent run
length which may restrict air ﬂ ow it is recommended
that a contractor install a power vent. When a contrac-
tor has found it impossible to vent straight through the
roof power venting is recommended to help eliminate
exhaust restriction of this natural draft machine. This
draft inducer (power vent) must be installed by a li-
censed contractor who can calculate size, operation
connections and associated dampeners. Since we
are a manufacturer and not a licensed contractor and
as such we are unable to make recommendations for
suitable make and model of power vents and compli-
ance with local building codes.
Damper: An exhaust stack can reduce thermal ef-
ﬁ ciency by drawing in too much combustion air. This
can be controlled by adding a damper just below the
draft diverter. 8.753-473.0 - 8" Damper, 8.753-474.0
-10" Damper, 8.753-418.0 - 12" Damper.
NOTE: Closing the damper can create high levels of
CO in the exhaust. Adjustments to the damper should
only be performed by a trained technician using a ﬂ ue
gas analyzer. If an analyzer is not used the damper
should be set in the fully open position.
Sampling Port: A port for sampling ﬂ ue gases and
measuring the ﬂ ue gas temperature should be placed
18" above the ﬂ ue collar. The port should be covered
when sampling is not being performed. The size of
the port should be only slightly larger than the probe
for the ﬂ ue gas analyzer.
Rain Cap: A rain cap should be installed on top of
the stack to prevent rain water, leaves and debris from
entering the stack. Your installer may also recommend
specialty caps for high wind areas or cold weather
zones to help prevent back drafting. 8.717-731.0 - 10"
Raincap, 8.717-732.0 - 12" Raincap.
The water source for the machine should be sup plied
by a 5/8" I.D. gar den hose with a city water pressure of
not less than 30 PSI. If the water supply is in ad e quate,
or if the garden hose is kinked, the machine will run
very rough and the burner will not ﬁ re.
Connect the high pressure hose by pulling the cou pler
col lar back and then inserting it onto the dis charge
nip ple. Se cure it by pushing the collar forward.
Attach the wand into the spray gun using teﬂ on tape
on the pipe threads to avoid leaks.