Abstract: A terminal unit for a balanced flue has an air inlet duct (10) and an outlet duct (20) projecting beyond the mouth of inlet duct. An elliptical plate (30) encloses a region around the outlet duct to inhibit combustion products for entering the inlet duct. Alternatively a circular plate (60) could be used.

Abstract: A control valve system for a gas-fired, instantaneous water heater is disclosed. The valve has a "snap" action constructed to inhibit the supply to the burner of insufficient amounts of gas to ensure reliable ignition. In one example, a flexible diaphragm has opposite sides connected via respective passages to receive pressures upstream and downstream of a restriction in a water flow path. The diaphragm opens a gas valve in response to a predetermined flow of water along the path. In order to provide the "snap" action, a further passage is provided that links the two passages coupled to the diaphragm and contains a ball that can block the further passage only when the water flow is sufficient to open the gas valve sufficiently for an ignitable quantity of gas to flow to the burner.

Abstract: A burner formed from a sheet metal pressing doubled over to define a gas manifold has alternating flame ports 15 and 16 along one edge. Between the flame ports curled over tabs 19 and 20 define horizontally-directed retention flame ports 21. The tabs 19 and 20 also serve to clamp the edges of the pressing together against the strains of thermal cycling, eliminating the need for spot welding.