High efficiency furnace

Claim 1

A furnace comprising: an exterior housing having means for introducing air to be heated and means for discharging heated air from the furnace; at least one clam-shell type primary heat exchanger having a combustion chamber for the ignition of fluid fuel yielding hot combustion gases in a lower end and an exhaust outlet in an upper end; a secondary heat exchanger having an inlet for receiving the combustion gases produced in the primary heat exchanger in an upper end communicating with the exhaust outlet of the primary heat exchanger and a secondary exhaust outlet in a lower end, and being parallel to the primary heat exchanger, said primary and secondary heat exchangers being vertically oriented relative to the furnace housing; a tertiary heat exchanger for receiving combustion gases and condensate from the secondary exhaust outlet, comprising a pair of spaced apart opposed manifolds, a plurality of parallel condensation tubes interconnecting the manifolds, and drainage means for removing the condensate from the manifolds, the tertiary heat exchanger oriented approximately perpendicular to the primary and secondary heat exhangers, horizontally relative to the housing, below the combustion chamber of the primary heat exchanger, and below the secondary exhaust outlet; exhaust means communicating with the tertiary heat exchanger for removing combustion gases from the housing; and an induced draft blower for (a) drawing combustion gases through the primary, secondary and tertiary heat exchangers, (b) inducting sufficient air to the combustion chamber of the primary heat exchanger for efficient combustion, and (c) forcing the combustion gases through the exhaust means.