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Honeywell Brand Modulation Motor:
The modulating motor can be operated by removing the
cover, and removing the yellow wire to drive the motor to
the high fire position. Connecting the yellow wire will cause
the motor to drive to low fire position. This is a low voltage
(24 VAC) wire that can be handled safely, however, care
must be used as high voltage is also present.
Figure E-3 Multiple Setpoint Modulation Motor (Siemens)
Siemens Brand Modulation Motor:
This motor has multiple set points, one for gas and one
for oil. Removing the cover will expose a manual/auto
switch that will allow the motor to be cycled manually to
check the linkage and valve positions.
CAUTION
IN MANUAL POSITION, END STOPS DO NOT LIMIT
TRAVEL ON THE MULTIPLE SET POINT
MODULATION MOTOR. MONITOR AND DECREASE
TRAVEL IF THE VALVES APPROACH FULL TRAVEL
TO PROTECT THE VALVES FROM DAMAGE.
Flexible Strip
Retention
Plate
JBE(X) Manual
Figure E-3 shows the internal settings of the multiposition
modulation motor. Each adjustable cam setting is related
to an electrical connection (or circuit in motor). These
circuit numbers are listed on the wiring diagram so that
the low and high points of each fuel are identified. These
would be adjusted independently to obtain the input rates.
The valves and linkage should operate smoothly without
strain or jerky actions. If this occurs, check for binding
linkage and rod ends that are not within their range of
Adjusting Wheel
motion and readjust as required.
Matches Adjacent
Circuit
If the burner is equipped with FGR, the FGR valve will
Circuit Designation
modulate with the fuel and air valves and it should travel
Shown on Wiring
from the near closed low fire position to a position that is
Diagram
about 45 to 90 degrees open at high fire. Dual fuel units
can have additional controls, preventing or limiting FGR
from flowing during oil firing. Some FGR units (designed
for 30 ppm NOx or lower on natural gas) will be 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 input
close to the gas input (lowering the FGR rate increases
the combustion air rate). The oil combustion is generally
better when some FGR is used at low rates thus NOx
level will be reduced.
Cam
Cam Set Screws
Adjusting Screws
Aluminum Strip
End Screws
Spring
End Screw
Adjusting Nut
Cam Follower
Roller Washers
Figure E-4
Fuel Cam Adjustment
Page 36
Roller
Cam Follower
Section E - Preliminary Adjustments
Return
Springs
Jack
Shaft
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