ENG • 9.801-511.0 • Rev. 9/13a
13
PRESSURE
W
ASHER
DEALE
R’S MANU
AL
Inspection and Testing Gas Piping:
The building structure should not be weakened by
installing the gas piping. The piping should not be
supported by other piping, but should be firmly sup-
ported with gas hooks, straps, bands or hangers. Butt
or lap welded pipe should not be run through or in an
air duct or clothes chute.
Before turning gas under pressure into piping, all open-
ings from which gas can escape should be closed.
Immediately after turning on gas, the system should
be checked for leaks. This can be done by watching the
1/2 cubic foot test dial for 5 minutes for any movement
or by soaping each pipe connection and watching for
bubbles. If a leak is found, make the necessary repairs
and repeat the above test.
Defective pipes or fittings should be replaced and not
repaired. Never use a flame or fire in any form to locate
gas leaks — use a soap solution.
After the piping and meter have been checked com
-
pletely, purge the system of air.
DO NOT
bleed the air
inside an enclosed room.
During pressure testing of the system at test pressures
in excess of 1/2 PSIG, the pressure washer and its
individual shut-off valve must be disconnected from
gas supply piping system or damage to the gas valve
will occur.
Gas Pressure:
The incoming gas pressure must be a minimum of
9.0 wc-in and must not exceed 13.8 wc-in or ½ psig
to the control valve. Line pressure above ½ psig must
be regulated prior to the machine. The ideal supply
pressure is 13.0-13.5 wc-in. If the required BTU input
can not be achieved consult the factory for instructions
regarding changes to the nozzle orifice size and an
appropriate manifold setting.
NOTE:
Any changes to the burner and manifold pres-
sure setting should only be performed by a trained
technician and adjusted using a flue gas analyzer.
The manifold pressure has been preset at the factory
according to the table below for optimum operation at
sea-level. The manifold pressure and BTU input will
be listed on the specification plate for the machine.
For Tech Tip Instructions
Combustion efficiency in a natural draft pressure
washer is significantly influenced by the heat created
inside the coil, the design of the coil and flue and the
length and diameter of the exhaust stack. The table
below shows data included in the operator’s manual
for flue and stack sizes and gas manifold pressure
settings. These sizes are critical for achieving proper
combustion and acceptable emissions.
NG
LP
Model
Collar Stack wc-in kBTU-in wc-in kBTU-in
3.5@2000
10"
8"
3.6
320
7.8
321
3.9@3000
10"
8"
3.4
310
7.4
310
4@2200
10"
8"
5.1
364
11.2
364
4.8@3000
10"
10"
4.2
415
9.1
415
5.0@2300
10"
10"
4.7
439
9.5
439
6.3@3200
12"
10"
4.3
507
7.4
507
8@3200
12"
12"
3.1
658
7.0
658
9.5@3000
12"
12"
5.4
816
10.0
816
Testing has shown that simply adding a 36” stack
extension to the flue adapter on top of the pressure
washer can reduce the outlet temperature by 5-10°F.
This occurs by inducing a higher pressure differential
at the exit of the coil and increasing the flow of air into
the combustion process and through the stack. Most
or all of the lost outlet temperature can be recovered
by installing and adjusting a damper in the stack.
However this adjustment must only be performed by
a trained technician using a combustion analyzer. An
adequate combustion analyzer can be purchased for
a little at $500 (Bacharach Fyrite Tech, Testo 310).
The analyzer must determine percent oxygen and/or
percent excess air as a minimum.
The damper should be installed 24-36” above the flue
adapter. The pressure washer can be operated safely
with the damper fully open but with the lower outlet
temperature. If the damper is closed too far there will
not be enough oxygen to burn all of the fuel. This will
cause higher and potentially dangerous levels of CO
in the flue gas emissions.
To adjust the damper for proper combustion and ef-
ficiency perform the following:
1. If there is no sample port for the analyzer probe,
drill a hole slightly larger than the combustion analyzer
probe through the exhaust stack at a point about 18”
above the flue adapter.
2. Insert the probe of the combustion analyzer so
that the tip is at the center of the stack.
3. Open the damper to the fully open position.
4. Start the pressure washer and allow it to heat up
for at least 20 minutes before making any adjustments.
5. Note the values for % Excess Air and/or % Oxygen.
6. Close the damper in small increments until %
Excess Air is between 20-30% and/or % Oxygen is
4-5%.
INSTALLATION
