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4.0 Start-Up And Adjustment
Step 2: Adjust Low Fire Air Setting
Low Fire Air Differential Pressure Must be a minimum of 0.2" w.c. (0.5 mbar), which is obtained with the air butterfly
50 through 600 Sizes
1. Drive the control motor to fully closed or 1" w.c. (2.5 mbars).
50-600 Sizes: The slot on the end of the shaft is parallel to the plane
of the butterfly.
750-2500 Sizes: A roll pin embedded in the shaft is parallel to the
plane of the butterfly.
2. Loosen the setscrew on the motor side of the flexible coupling.
3. Measure air differential pressure as shown above. Differential pres-
sure will be approximately 0.2" w.c. (0.5 mbar) with neutral chamber
pressure. Differential pressure will vary with changes in chamber
pressure, but should never be less than 0.1" w.c. (0.25 mbar).
4. Hold the shaft firmly in place and tighten the setscrew. To avoid
backlash in two-piece couplings, put slight pressure on the motor
side of the coupling in the direction shown by the arrow before
tightening the setscrew.
Note: Arrows apply to motors which rotate counterclockwise to low fire. Reverse all arrows for clockwise motors.
(continued)
Measure differential air pressure as shown below.
valve in the fully closed position under neutral conditions.
Cycle the control motor several times, checking high and low fire differential
pressures. If they don't repeat, check for a loose valve shaft coupling or binding
of the motor or valve.
Tap "A"
Measure air differential pressure
between this tap and a tap
in the chamber wall
Low Fire Air Adjustment
9
750 through 2500 Sizes
Air Butterfly
Inside Burner
Coupling
Loosen This
Set Screw
750 thru 2500 RM:
Control Motor
50 thru 600 RM:
Slot Parallel
To Butterfly
Roll Pin Parallel
To Butterfly
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