Forced air heating fireplace unit

In a heating system for installation in a building during the erection thereof, the combination with a building having a plurality of separate rooms and equipped with an open fireplace in one room having a vertically disposed chimney thereabove, a metal open front firebox unit arranged in said fireplace and comprising a generally rectangular inner firebox unit mounted therein, the side and rear walls of said inner unit being spaced from the corresponding walls of said outer housing, the latter having an open upper end, main heat duct means connected to said open upper housing end for transmitting heat to said rooms, exhaust flue means in said chimney opening into the upper wall of said inner unit, air duct means opening into the upper end of said exhaust flue and projecting vertically downwardly exteriorly and rearwardly of and terminating above the lower end of said outer housing, air distribution chamber means at the lower end of and communicating with said air duct means, a fire grate arranged on the bottom of said fireplace, relatively short spaced air tube means extending forwardly and generally horizontally from said distribution chamber means into the lower end of said inner firebox unit and terminating beneath said grate and generally in the middle thereof, spaced transversely aligned air conducting tube means extending angularly through the front and rear walls of said inner firebox unit adjacent and spanning the upper end thereof, fan casing means having powered blower fan means associated therewith arranged rearwardly of said outer housing and extending thereacross beneath said distribution chamber means and communicating with the spacing between the side and rear walls of said inner and outer units, a plurality of conductive (spaced) metal plate heating core units spacedly and uniformly arranged on and generally covering each of the walls of said inner unit, each of said units including a series of relatively thin heat conductive plates arranged in uniformly closely spaced parallel relation whereby, when a fire is burning in the lower end of said firebox unit and said blower fan means is functioning, warm air and unburned gases exiting through said exhaust flue means will be drawn downwardly through said air duct means into said air distribution chamber means and introduced through said short air tube means into said inner firebox unit beneath the fire therein to enhance combustion, and simultaneously therewith fresh air will be directed by said blower fan means into said fan casing means and circulated upwardly between the walls of said inner unit and housing and between the plates of each of said heating core units so as to be heated thereby and through said spaced angular air conducting tube means for further heating and flow into said main heat duct means, said fireplace opening having warm air discharge means associated therewith and communicating with said main heat duct means and alignable with said spaced air conducting tube means for discharging heated air therefrom into the area in front of said fireplace.