Open in this
Figure 4.1. Air Butterfly Valve Open Direction
Step 2: Set Low Fire Air
1. Start combustion air blower.
2. Drive control motor to low fire position.
3. Measure the air differential pressure between Tap C
and the combustion chamber.
NOTE: The pressure tap is in the open position when the
screw inside the tap is unscrewed approximately 1/2 turn.
Do not remove the screw. Be sure to tighten the pressure
tap screw clockwise to the closed position after pressure
measurements have been taken.
Figure 4.2. Air Differential Pressure
4. Set low fire air.
a. Loosen the set screw on the burner side of
There is a slot in the end of the butterfly valve shaft
that is parallel to the air damper. This slot is used for
visual indication of the butterfly valve position. The
butterfly valve is closed when the shaft slot is
perpendicular to the direction of air flow through the
b. Rotate the air butterfly valve shaft to a fully closed
position. (Holes in the butterfly valve will supply low
c. When firing into a positive chamber pressure, rotate
the air butterfly valve from the closed position in the
direction of actuator travel to obtain a minimum
0.3" w.c. (0,8 mbar) air differential pressure.
d. Hold the butterfly valve shaft firmly in place and
tighten set screw .
High fire air adjustment is not required if the burner is firing
into a neutral pressure chamber and a 90° travel control
motor is used. It may be necessary to limit control motor
stroke to less than 90° if firing into a large negative
chamber. Contact Eclipse for further information.
Figure 4.3. Air Butterfly Valve Adjustment
5. Verify high fire air:
a. Drive control motor to high fire, full open.
b. Compare the high fire air differential pressure
between Tap C and the combustion chamber to the
approximate datasheet chart "Air Δp vs. Input". If
high fire air is insufficient, refer to section 5,
"Troubleshooting & Maintenance", in this document.
6. Return the control motor to the low fire position.
7. Close the pressure taps.