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7. After the burners have been lit for at least 90 seconds, observe the flames through the burner
viewing ports located on each side of the combustion air blower.
The air/gas mixture is properly adjusted when the burner manifold pressure is in accordance with
the applicable table on page 1-6 and the burners display a bright orange-red glow. If a blue
flame is observed or if there are dark spots on a burner face, the air/gas mixture requires
adjustment.
Adjusting the Air/Gas Mixture
On the side of the blower housing opposite the motor is a shutter plate with a locking nut.
Loosen the nut enough to allow the shutter to be moved, then adjust the position of the shutter to
open or close the air intake opening until a bright orange-red glow is obtained. Carefully hold
the shutter in position and tighten the locking nut.
Loosen this nut and
rotate shutter to open
or close air intake.
Right
Viewing
Port.
Left Viewing
Port is behind
motor.