Webster JB Series Installation, Startup, Operation And Maintenance Manual page 34

equipped with Posi-Control can be adjusted for individual air
and FGR settings on both fuels and can easily handle these
variations, even with lower NOx levels. Linkage burners op-
erating at 30 ppm NOx (natural gas) are equipped with a
potentiometer in the control panel that will allow the shut-off
valve to partially open and allows a small amount of FGR to
flow when firing oil. This keeps the oil inputs close to the gas
input (lower FGR rates increases the combustion air rate).
The oil combustion is generally better when FGR is used at
low rates resulting is a lower NOx level. Linkage levels with
NOx levels under 30 ppm will also use a multiple modulation
motor to provide separate gas and oil low fire and high fire
positions.
Linkage dual fuel units may also be equipped with the op-
tional multiple set point (Landis) modulation motor in addition
to the above potentiometer. This motor allows for different
low and high fire settings on gas vs oil to obtain the correct
airflow for each fuel and optimize the turndown on gas.
On a dual fuel unit, the natural gas should be done first to
properly set the FGR inlet tube. Once gas is setup, oil can
be set.
For dual fuel linkage systems, the following guidelines
should be used:
• A 60 ppm system can be adjusted with the same FGR rate
on both fuels. The FGR control valve is set on gas and oil
follows that setting.
• A 30 ppm system uses the FGR limiting potentiometer
(located in the control panel) to obtain a partial flow of FGR
when firing oil. The FGR control valve is set when firing
gas. The FGR limiting potentiometer is adjusted to improve
combustion but not cause instability. The combustion needs
to be checked at several firing rates.
• Under 30 ppm, separate gas and oil operating points are
established in the modulating motor. Parallel positioning
(linkageless) systems allow all of the valves to be positioned
independently for each fuel. For this reason, the setup se-
quence can be more flexible.
5. Burner Drawer Adjustments
The burner drawer has several adjustments built into the de-
sign that allow the combustion to be tuned. While this can
simplify the combustion tuning process, care must be used
to retain the relative position of other components during this
sequence. If these adjustments are required, follow the se-
quence listed to perform the adjustments.
Before any adjustments are made, the position of each com-
ponent must be marked. A felt tip pen or a combination of
masking tape and another type of pen can be used.
• Mark the distance of the oil gun tube from the backplate.
• Mark the distance of the gas pilot line to the backplate.
a. To adjust the diffuser to inner fire cylinder dimension:
• Measure the dimension from the backplate to the end of
the oil gun tube. This dimension, along with the initial posi-
tion will determine the limit of the adjustment. For example,
if the diffuser is 1 inch behind the fire end of the inner fire
cylinder, then it can be adjusted in 3/4 inch or out 1/2 inch to
stay within the limits of 1/4 inch to 1 1/2 inch diffuser to fire
JB Manual
end of the inner fire cylinder dimension.
• Loosen the two setscrews locking the pilot gas line
and gun tube to the backplate.
• Adjust the diffuser by moving the oil gun tube in and
out the amount determined above. When the best posi-
tion is found, lock into place with the two setscrews on
the oil and pilot tubes.
b. To adjust the oil nozzle to diffuser position:
• Adjust the oil nozzle to obtain the best combustion.
• Watch for spray back on the diffuser when the oil noz-
zle is pulled too far back. The flame may appear good
but carbon will quickly develop on the diffuser.
• The drawer assembly must be removed to adjust the
oil nozzle to diffuser position.
The burner drawer must be removed for access to com-
ponents, follow the following steps:
a. Disconnect the gas pilot line. Move the pilot line so
the drawer can be pulled out without interference.
b. If equipped with oil, disconnect the oil line(s), and
move the oil line out of the way to allow the drawer to
be pulled.
c. Loosen and remove the screws on the burner draw-
er.
d. Disconnect the ignition cable from the drawer assem-
bly. It is attached with a snap-on fitting.
e. Pull the drawer out, holding the drawer centered in
the opening to prevent it from hanging up while being
pulled out.
f. Disconnect the scanner by screwing it off of the scan-
ner tube. In some cases, the scanner simply pulls out,
with a spring tension. Secure the scanner so that it is
protected from shock.
g. Set the drawer down horizontally, do not set it on the
diffuser as it may flatten some fins or change positions.
To re-install the burner drawer, simply work the proce-
dure in reverse.
6. Single Fuel Setups
Single fuel burners can be adjusted following the proce-
dures outlined in Section 10 for gas firing; Section 11 for
pressure atomized oil, Section 12 for Air atomized #2 oil
and Section 13 for heavy oil firing.
The procedures for each of the systems (linkage, cams,
FGR) must be completely understood and followed as
part of the setup process.
7. Combination Gas and Pressure Atomized Oil
Combination burners, firing both gas and oil, require
some compromises in the setup because they share
common controls for both fuels. In this case, linkage
units must have the gas input adjusted to match the oil
inputs because there is little flexibility in adjusting the oil
rates. Oil will be setup first and will set the air damper
positions to support the low and high fire oil inputs. Fol-
low the procedure outlined in section 11 to complete the
oil setup. Then setup the gas input as defined in section
Page 34 Startup and Operating Adjustments