Abstract: Disclosed is a heating device of assembled cast panel construction with flanges joined together and whose front, side, back and top walls and bottom grates define a combustion chamber. The angled side walls define an obtuse interior angle and the side and top walls define an obtuse interior angle. An embodiment of the heating device is a boiler incorporated by operatively connected expansion tank, holding tank and a coil of water tubes disposed in the combustion chamber's top area. Another embodiment of the heating device is a hot-air furnace incorporated by a plenum chamber, cold-air return and blower fan with such blower fan directing cold air from the cold-air return to and through the plenum chamber where it is heated. A still further embodiment combines the boiler and hot-air furnace with such heating device.