My home is equipped with a make-up air line intended to bring some outside air to mix it with indoors air prior conditioning by the furnace. I am not sure why this is necessary but my question is regarding calibration. The line is connected to a Skuttle Model 216 make-up-air control unit. See:
In summary, a damper inside the duct is moved when the furnace blower operates allowing outside air in. When the blower stops, the damper moves again to obstruct the flow of outside air. The damper can be calibrated with a pair of counterweights in the outside of the unit (see patent). I have followed the manufacturers instructions for calibration and failed every time. Either the damper wants to stay closed or it wants to stay open. I cannot get it to adjust according to the blower power. Does anybody has any experience with these units? Any ideas on proper calibration or on what could go wrong with these devices?