Abstract: A fuel-fired water heater has a combustion chamber disposed above a wall ucture forming a flow path for combustion air being drawn into the combustion chamber during firing of the fuel burner portion of the water heater. A combustion air shutoff system is incorporated in the water heater and functions to sense an undesirably high firing temperature in the combustion chamber and responsively shut off essentially all further air flow to the combustion chamber and thereby terminate combustion therein. In various disclosed embodiments thereof, the combustion air shutoff system includes a damper member movable between an open position in which its permits air flow through the combustion air flow path, and a closed position which it blocks essentially all further air flow through the combustion air flow path. The damper is releasably held in its open position by a eutectic metal fusible link member positioned exteriorly adjacent an exterior wall of the combustion chamber.

Abstract: A fuel-fired water heater has a combustion chamber disposed beneath the storage tank portion of the water heater. The bottom side wall of the combustion chamber is defined by an annular perforated wall structure with a perforated mounting plate structure being removably secured to the underside of the wall structure over the central opening therein. A burner and associated pilot/thermocouple assembly are secured to the upper side of the mounting plate and project upwardly into the combustion chamber, with the piping and wiring of the burner and pilot/thermocouple assembly extending externally beneath the combustion chamber, outwardly through a side wall access passage, and then turning upwardly along the outside of the water heater for connection to a thermostatic fuel valve. To remove the bottom plate-mounted burner and pilot/thermocouple assembly the fuel supply piping must first be decoupled from the thermostatic valve, thereby assuring that the access plate cannot be removed while the burner is firing.