Abstract: An air to gas mixing valve is provided for fireplaces especially those having sealed combustion chambers as employed in direct vent fireplaces. The novel mixing valve comprises a channel shaped shutter which mounts on and is linearly slidable over a window or windows made a part of the gas mixing pipe which connects to the fireplace burner. An adjustment rod is rotatably coupled to an actuating arm on the channel shaped shutter and extends through at least one sealed panel and has a rotatable nut or screw for linearly moving the shutters over the windows from a remote position.

Abstract: In the particular embodiment described in the specification, a cold hearth arrangement has a hearth plate forming a floor above the bottom of a melt chamber enclosure and a hearth is removably mounted on the hearth plate. Coolant supply and return lines are connected through the hearth support plate to the bottom of the hearth so that no utility lines are exposed above the floor plate. A mold, which also has water supply and return lines connected to it beneath the floor plate extends through the bottom of the enclosure.

Abstract: The present invention includes a universal combustion chamber preferably shipped from a factory as a separate unit for field installation into a plurality of different fireplace units and includes a top panel and a floor panel connected to sidewall panel to form a complete ready to use gas tight structure. The combustion chamber is fabricated from flat and/or curved panels which are preferably molded from a thick paste slurry of mixed vitreous alumina silicate fibers combined with an aqueous solution of silica binder and fired to form non-porous gas tight panels which are interconnected to form a gas tight combustion chamber. The connecting joints are preferably reinforced by the addition of a high temperature adhesive added to the mating joints. The joints may be further reinforced and/or sealed by mechanical reinforcing at or in the joints. The joints may be eliminated by forming a one piece combustion chamber on forming molds that are designed to be separated from a formed but uncured combustion chamber.