18
Operations
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 accept-
able emissions.
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 techni-
cian using a combustion analyzer. 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 effi-
ciency 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%.
This process can also be used when turning down the
firing rate for high altitude installations above 2000 ft.
1. Adjust the gas pressure down 4% for every 1000 ft
of elevation.
Example: Recommended firing rate for a 4.8@3000 is
4.2 wc-in. For an installation at 3500 feet reduce this
pressure by 16% by setting the manifold pressure to
4.2*.84 = 3.5 wc-in.
A manometer capable of reading to at least the nearest
0.1 wc-in will be required for this adjustment.
2. Follow steps 1-6 above to optimize the outlet
temperature of the pressure washer.
Installations Above 2000 ft
Installation at altitudes greater than 2000 ft will require
adjustments to the gas manifold pressure.
For installations above 2000 feet the firing rate should be
reduced by 4% per 1000 feet. Example: Recommended
firing rate for a 4.8@3000 is 4.2 wc-in. For an installation
at 3500 feet reduce this pressure by 16% by setting the
manifold pressure to 4.2*.84 = 3.5 wc-in. This adjustment
should only be made by a properly trained service tech-
nician. A manometer capable of reading to the nearest
0.1 wc-in will be required for this adjustment.
In Canada, certification for installation at altitudes over
4500 feet is the jurisdiction of local authorities.
Gas Valve Replacement
If you replace your gas valve the manifold pressure for
the new valve will need to be adjusted to match the spec-
ification plate for the machine. Follow the installation and
adjustment instructions provided with your replacement
valve. A manometer capable of reading to the nearest
0.1 wc-in will be required for this adjustment
CAUTION: All gas conversion must be done by a
qualified service person in accordance with these
instructions and in compliance with all codes and
requirements. In Canada, gas conversion shall be
carried out in accordance with requirements of the
Provincial Authorities having jurisdiction and in
accordance with the requirements of the CAN/GGA-
B149.1 and .2 installation code.
Landa ENG Operator’s 9.801-511.0 - F
NG
LP
Model
Coll
a
r
St
a
ck
wc-in
kBTU-in
wc-in
kBTU-in
3.5@2000
10"
8"
3.6
310
7.8
310
3.9@3000
10"
8"
3.4
354
7.4
354
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
437
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
775
Summary of Contents for ENG Series
Page 36: ...9 801 511 0 Printed in U S A...
