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IC-SA-1511 (02/2014)
V/LNV Series Manual
4-21
Adjustments
The modulating motor will be stopped at the end of its stroke by an internal limit switch. Combustion gas
analysis indicates the air to fuel ratio and the degree of complete combustion. The closer the rod comes to
parallel with the lever, the slower the rod moves. The angles of the driven levers on the jackshaft can be
adjusted to vary the rate of change. The closer the rod to the hub of the lever, the less distance it will travel.
Increasing the lever length on the damper, metering unit and valve(s) decreases flow rate.
FIGURE 4-24.
Linkage Adjustment
4.8.2 — Cam Trim Adjustment
After low and high-fire adjustments are complete, final adjustment is made with the cam assembly to obtain
a good air-fuel ratio throughout the entire firing range. The input of combustion air is fixed at any given point
in the modulating cycle. The fuel input may be varied to obtain correct flue gas readings. The adjustment is
made to the metering cam by means of the 14 adjusting screws which are turned in (clockwise from the
hex-socket end) to increase the flow of fuel, and out (counterclockwise from the hex-socket end) to
decrease it. A 3/32” hex key is required. It will be necessary to cut off the short end of a hex key to
approximately 3/8” to adjust the first two socket head setscrews at the low-fire position. Take a combustion
analysis at various points of the cam profile. Adjustment can be made without cycling the burner, then
operate the automatic modulating cycle to assure satisfactory results. Tighten the locking setscrews.
NOTE:
It is essential that the cam spring, cam follower bearing wheel, and cam follower arm at the pivot point
be greased sparingly every month to ensure smooth operation of the cam assembly. Regular automotive
bearing grease should be used.
A
B
TYPICAL LINKAGE
ADJUSTMENT
"DRIVING"
DECREASE
INCREASE
INCREASE
DECREASE
TYPICAL LINKAGE
ADJUSTMENT
"DRIVEN"
GAS VOLUME
CONTROL
VALVE
FUEL OIL
UNIT
OIL
METERING
VALVE
AIR INLET
HOUSING
MODULATING
MOTOR
656-10218-000