Fireplace insert with forced air flow heat exchanger

A fireplace insert having an inner firebox including inner bottom, top, rear and opposite side walls interconnected along adjacent marginal edge portions to form a combustion chamber therein, an outer housing for snug reception within a fireplace, said housing including outer bottom, top, rear, front and opposite side walls, said firebox being received within said housing with the front thereof closed by the front wall of said housing and at least major portions of said inner bottom, top, rear and opposite side walls spaced inwardly from opposing portions of said outer bottom, top, rear and opposite side walls, means dividing the space between said inner and outer bottom walls into a central front-to-rear extending ash pit closed at its rear end from the space between said inner and outer rear walls and a pair of opposite side front-to-rear extending air passages closed along their upper portions from the side spaces thereabove defined between corresponding inner and outer side walls of said firebox and housing and opening rearwardly into the rear space between said inner and outer rear walls, said inner bottom wall having an opening formed therein opening downwardly into said ash pit and equipped with a grate, said front wall having a lower central opening formed therein registered with the front end of said ash pit, an ash drawer slidably received in said ash pit for removal through and removably closing said lower central opening, an access opening formed in said front wall above said lower central opening for providing access to the interior of said combustion chamber through said front wall, an access door removably closing said access opening, the rear ends of said side spaces being closed from said rear space and open to the upper space between said top walls, means closing the forward portion of the upper space between said top walls and defining a flue gas outlet opening upwardly from said firebox through a forward portion of said housing top wall, air outlet means opening forwardly through said front wall on opposite sides of said access opening from the forward portions of said side spaces, air pump means operatively associated with said air passages for pumping air therethrough into the opposite side lower portions of the rear space between said rear walls, from the upper portions of said rear space into the rear portion of said upper space, from opposite sides of said upper space down into the upper portions of said side spaces and forwardly from the latter through said air outlet means.