Patent ID: 8807990

Claim:
In a condensing gaseous fuel fired furnace having a flue gas vent conduit, the improvement comprising: an adjustable flue gas flow restrictor dividing said flue gas vent conduit between a flue gas upstream side and a flue gas downstream side, said flue gas flow restrictor operable for modifying an opening size of a flue gas opening for passage of flue gas in said flue gas vent conduit from said flue gas upstream side to said flue gas downstream side; and a liquid condensate bypass conduit having a condensate inlet in fluid communication with said flue gas vent conduit at said flue gas downstream side and a condensate outlet in fluid communication with said flue gas vent conduit at said flue gas upstream side, and providing a condensate pathway separate from said flue gas vent conduit and said flue gas opening for transmission of condensate from said flue gas downstream side to said flue gas upstream side.