Heating unit

DETAILED DESCRIPTION Referring now to the drawings: In the illustrated preferred embodiment, the fireplace heater unit 10 of the present invention includes a box 11, of generally rectangular shape.
As shown, the box has a bottom 11a, upstanding, spaced apart sidewalls 11b; a back wall 11c; a partially open front wall 11ad; and a partially open top 11e with the sidewalls, back wall and front wall interconnected by the bottom and top.
The box 11, is shaped to fit the opening of a conventional fireplace and, so constructed, it may be built into a fireplace opening, may slide into a pre-existing fireplace, or may be used as part of a free-standing fireplace.
The box may contain openings for clean-out purposes, the same as are generally provided in fireboxes of conventional fireplaces.
The inside of the box forms a combustion chamber 11f.
A short distance from the front wall 11d and at the top 11e an opening 12 extends to the back wall 11c and to each sidewall 11b, to form a chimney opening.
An outer wall 13 cooperates with the back wall 11c of the box 11 to form a back air chamber 14.
An intake duct 14a having its intake outside of the building in which the unit is used, is connected into the back air chamber.
Slightly above the top 11c, and extending across the chimney opening 12,, on the line 2--2 of FIG.
1, are a series of tubes 15.
The tubes 15 each open at one end into the back air chamber 14 and at the other end into a front air chamber 16.
The tubes 15 are held in place by vertical projections 17 that extend from the top 11e of the box and around the chimney opening 12 and that seal the front air chamber from the chimney opening.
The front wall 11d extends vertically a short distance above the top 11e to the same height as the vertical projections 17.
An outer top wall 18 rests on top of the vertical projections 17 and the vertical extension of the front wall 11d.
The outer top wall 18 has a hole 18a therethrough to form a chimney opening.
Wall 18 seals the front air chamber 16 and the back air chamber 13 from the chimney opening 12, thereby insuring that combustion gases do not intermix with heating air