Abstract: The invention provides an instantaneous water heater which includes safety devices separately or in combination to prevent the explosion of the heat exchanger in the event of an excessive heating of the water in the heating coil and to shut-off the flow of gas to the burner in the event the atmosphere surrounding the water heater presents a dangerous decrease of its oxygen content or an excess CO/CO.sub.2 content, thus avoiding the risk of asphixiation or intoxication to the user. Additionally, the main gas flow control valve includes a settling chamber for separating the solid particles entrained in the combustible gas and preventing the obstruction of the internal gas passages in the gas control valve, as well as the plugging of the gas injectors of the pilot flame and/or burner nozzles.

Abstract: A multichamber gas control valve modulates and controls the flow of gas to the burner of an instantaneous water heater. Flow of gas from an inlet chamber to a first chamber of the valve is controlled by a thermostatic valve and gas flow from the first to a second chamber is controlled by a temperature controller. Gas flow from the second chamber to an outlet chamber is controlled by a spring biased valve actuated by a diaphragm actuator operated in response to flow of water through a venturi in the water supply of the heater. The several chambers are in a common valve body closed by a removable cover to provide easy access to the components of the assembly.

Abstract: A venturi operated water flow responsive valve controls the flow of gas to the burner of an instantaneous water heater by controlling the flow of gas between chambers of a main control valve. The venturi operated valve is of the diaphragm type and the gas flow is controlled as a function of water flow rate.