TM 5-3895-374-24-2
ADJUSTING COMBUSTION MIXTURE
FULL MODULATION FIRING (NORMAL)
This method provides the user with a continuous range of firing rates Varying between what is
known as high and low fire. Unlike a two-stage burner, the modulator or damper motor on this unit
modulates the air shutters in response to the 4 to 20 MA signal from the temperature controller
instead of a simple switch. In fact, it is the temperature controller and the modulator motor that are
responsible for the continuous range cf firing rates.
The modulating air shutters may be adjusted by loosening the linkage and turning the stem to the
desired location. See Section 5.7 for instructions on adjusting linkage.
The fuel oil input may be adjusted by loosening the linkage on the oil metering valve, then adjusting
the operating shaft to increase or decrease the fuel oil flow capacity. See Section 6.13 for details
on the oil metering valve.
The linkage to the air and fuel valve may have to be adjusted to shorter or longer positions to
obtain an equal increase in air and fuel as the motor drives the linkage to high-fire position.
CAUTION
After any adjustments are made, be sure there is no binding of the linkage,
or damper motor stalling at any point of travel.
(page 3-947)
