Many furnaces operate with a cross-connected ratio regulator system to balance the air and gas flow for proper combustion. There are two devices in the gas train that must be set properly; the Limiting Orifice Valve (LOV) and the Ratio Regulator.
Start by moving the air flow valve to the High Fire position. Then, remove the cap on the top of the LOV. Inside is an adjustment screw. Turn the screw to move the valve up or down until you achieve the desired gas flow or pressure to the burner.
Then, move the air flow valve to the Low Fire position. Remove the cap on the bottom of the Ratio Regulator. Inside is an adjustment screw. Turn the screw to adjust the gas outlet pressure until you achieve the desired Low Fire gas pressure or flow.
Once the Low Fire setting is made, be sure to re-check the High Fire, as further adjustments may still be necessary. Replace the caps to protect the adjustments on the LOV and Ratio Regulator.
Contact #CICPittsburghLLC to help you with your annual burner tuning.