Toto Ltd.

Shigefumi Yasunaga

Osamu Tsutsui

Hidehiko Kuwahara

Shusaku Murakami

Hot water supply temperature is set by a temperature setting device in response to an instantaneous flow rate signal from a water flow rate sensor arranged in a water supply pipe and a feeding water temperature signal from a feeding water temperature sensor which are compared with a predetermined hot water supply temperature and calculated in a control unit. A proportional valve and other devices in a gas supply pipe are controlled in response to the result of the comparison and calculation to define a required volume of gas for ignition and heating. At the same time, a fan damper is controlled by a damper control device so as to adjust the volume of combustion air. A signal representing discharging hot water temperature from a discharging hot water temperature sensor arranged in a hot water feeding pipe is fed back to the control unit and calculated therein, and a valve in the hot water supply pipe is adjusted in response to the result of calculation to attain the desired hot water supply temperature. In order to prevent freezing in the system in winter season, a signal from a thermostat in the water feeding pipe is transmitted to a heater arranged in an air supply chamber so as to heat a heat exchanger pipe and, at the same time, heaters arranged in the water feeding pipe and the hot water supply pipe are also controlled to prevent freezing.

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Shiga, Japan

Shigefumi Yasunaga