Abstract: A device for converting an existing fireplace to an efficient space heater to fully utilize the heat generated by a fire therein without losing the aesthetic effect thereof is disclosed. The device includes a plenum chamber adapted to rest on the bottom surface of the fireplace, said chamber having a damper controlled draft inlet opening into the existing ash dump pit. The ash pit then serves as an air inlet conduit for air to be heated, and outside air may be supplied thereto by a fan. Pipes extend from the interior three edge portions of the chamber upwardly and around the fire wall and terminate framing the upper and side portions of the fireplace opening. A conventional fire grate is disposed on the upper surface of the chamber surrounded on three sides by said pipes. Air admitted to the plenum chamber then circulates through the pipes to be heated by a fire on the grate, and is then expelled into the room.

Abstract: An efficient zero clearance fireplace heating device is disclosed. The device includes a conventional metal firebox having closeable glass doors and a flue adapted to communicate with a chimney. The sides and bottom of the firebox are enclosed with mutually spaced metal walls to form a plurality of interconnected chambers for circulating either room air or outside air therethrough. A portion of the circulated air is returned to the room through a vent and a portion is admitted to the firebox for combustion air. The combustion air is initially directed across the interior surface of the glass doors to minimize blackening thereof by smoke from the fire. Baffles may be provided between walls of the interconnected chambers to provide a labyrinthian series of passages for air circulated therethrough whereby heat is exchanged between the walls and the circulating air so that the outside surfaces of the device remain sufficiently cool to permit installation adjacent combustible structural members.