Dim
Smaller
Larger
Angle A
Slower LF driven
arm travel (D)
Faster LF driven
arm travel (D)
Length B
Reduce driven
arm travel (D)
Increase driven
arm travel (D)
Length C
Increase driven
arm travel (D)
Reduce driven
arm travel (D)
b.
Decreasing the angle of the drive arm will slow the
initial valve travel (and speed up the travel at high fire).
This would be done to get the air damper to match the
fuel valve action.
3. Fuel Cam Adjustments
The cam is used to adjust the intermediate fuel rate with
the low and high fire settings done by the linkage connec-
tions. The intermediate rates can be adjusted by turning the
adjusting screws in the clockwise direction to increase fuel
input and decrease the % O2 level in the flue gases.
Turning the adjustment screws counterclockwise will
decrease fuel input and increase % O2 in the flue gases.
The following guidelines should be used for adjusting the
cam: (See Figure E-4)
a.
When adjusting the screws, the adjacent screws must
also be adjusted to provide a smooth contour from screw
to screw. When complete, the flexible strip between the
adjusting screws and the roller must come in contact with
each screw, providing a smooth transition from low fire to
high fire.
b
. The end screws (or nuts) can be adjusted to hold the
strip against the screws, but should not deform the strip.
c.
There should be no upsets in the profile, where the
Figure F-1
Linkage Adjustments
flexible strip is required to move to a screw position
where it is initially not in contact with the screw. Also,
the movement from one screw to the next cannot be
too large (more then 1/8”). This will cause the strip to
flex and will lead to premature failure of the strip.
d.
The adjusting screws have a limited range of
adjustment. They can be turned in until they are flush
with the aluminum bar and adjusted out until the side
washers of the roller contact the aluminum bar.
e.
If any adjusting screw does not turn with some
resistance, the cam must be replaced.
f. When the cam adjustment is complete, the
retention plate must be installed. The retention plate
will help insure that the fuel valve position will not get
far from its ideal position, even with interference or
sticky valve operation.
WARNING
IF THE CAM ADJUSTING SCREWS DO NOT HAVE
RESISTANCE TO TURNING, THE CAM SHOULD
BE REPLACED, AS THE SCREWS MAY CHANGE
POSITION. FAILURE TO CHANGE A DEFECTIVE
CAM MAY RESULT IN INJURY OR DEATH.
CAUTION
LARGE CHANGES FROM ONE ADJUSTING
SCREW TO ANOTHER WILL RESULT IN PREMA-
TURE FAILURE OF THE CAM AND MAY PREVENT
THE BURNER FROM OPERATING PROPERLY.
g.
If the contour has a sharp rise in the cam screw
profile, trying to open the valve very quickly in the first
few screws, the linkage should be readjusted to cause
the air damper to open slower (make the jackshaft
drive arm more parallel to the linkage rod). Likewise,
the opposite contour can be corrected by speeding up
the air damper drive (Figure F-1). The final cam screw
profile should be close to the profile of the cam with
no abrupt changes.
4. FGR Adjustments
Flue gas is recirculated back into the burner to reduce
the flame temperature, which reduces the NOx level.
High quantities of flue gas result in lower NOx levels,
but can also result in flame instability if there is too
much FGR. Natural gas fuel can handle larger
quantities of flue gas than oil and can have much
lower NOx levels as a result. Generally, the NOx l
evels only apply to gas firing and oil firing is not
adjusted for NOx levels. There may be exceptions
to this, and the orders details should be reviewed to
identify any special combustion requirements.
Dual fuel units may need additional adjustments
and compensation to handle the different FGR rates
between natural gas and #2 fuel oil. Units that require
gas NOx levels above about 45 ppm can operate with
the same quantity of FGR on both fuels and no
additional controls or adjustments are needed.
Page 41
Section F - Startup and Operating Instructions
JBE(X) Manual
Slower LF driven
arm travel (D)
Reduce driven
arm travel (D)
Increase driven
arm travel (D)
Faster LF driven
arm travel (D)
Increase driven
arm travel (D)
Reduce driven
arm travel (D)
Angle A
Length B
Length C
Modulating
Range 90°
B
C
D
A
Low
Fire
High
Fire
Linkage Arm
Drive Arm
Driven Arm
Jackshaft
Valve
(Air Damper,
FGR Valve,...
Dim
Smaller
Larger
