Adjustment Procedures
6-2
750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
6.2 — Linkage: Modulating Motor and Air Damper
The linkage consists of various arms, connecting rods, and swivel ball joints that transmit motion from the modu-
lating motor to the oil metering cam(s), to the rotary air damper, and to the gas butterfly valve, if used.
When properly adjusted, a coordinated movement of the air damper and metering cams within the limits of the
modulating motor travel is attained to provide proper fuel-air ratios through the firing range.
In linkage adjustments there are several important factors that must serve as guides:
1. The modulating motor must be able to complete its full travel range.
2. Initial adjustment should be made with the motor in full closed position, that is with the shaft on the power end
of the motor in its most counterclockwise position.
3. The closer the connector is to the drive shaft, the less the arm will travel — the closer the connector is to the
driven shaft, the farther that arm will travel.
FIGURE 6-1. Complete Linkage Assembly: Combination Gas and Oil
4. Overtravel linkage, where used, should not be required to extend its spring to the fullest stretch.
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