Abstract: A direct vent gas fireplace has a firebox surrounded by an enclosure. The enclosure has an inclined surface between the top, rear and sides. The surface is inclined at approximately 45 degrees and has an exhaust opening. The firebox has an inclined surface parallel to the inclined panel and has an aperture in each side of the firebox. A duct connects each of the apertures to the exhaust opening. A heat exchanger lies between the inclined surfaces in line with the duct. The surface has a gap in it which connects through an air combustion conduit to the bottom of the firebox. The conduit may be pre-formed. An angle adaptor has an inner cap over the exhaust opening and an outer cap over the inner cap and the gap. The adaptor may be mounted vertically or horizontally. Alternatively, an inclined plate may be placed over the inclined surface with a hole concentric with the opening and of greater area. A first wall of a double walled vent duct may enclose the opening, while the second wall encloses the hole.

Abstract: A furnace using pelletized wood as a fuel and a system for controlling the operation of the furnace are described. Pelletized wood stored in a hopper is fed into the combustion chamber of the furnace from an elevated position; and combustion of the pelletized wood is controlled by microprocessor-based circuit which receives input signals representative of the interior and exterior temperatures of the building, the air flow and the level of fuel in the combustion chamber and processes this information in accordance with a predetermined program to switch the furnace into one of two modes. In the `low` mode, the exterior temperature is below a certain value for example, 0.degree. C., but the interior temperature is above it. In this case a fire is maintained in the combustion chamber in anticipation of the interior temperature falling beneath this value.