PURPOSE: To save fuel, maximize a heat efficiency and at the same time automatically stop all operations where the temperature in a water room reaches an allowed temperature by automatically supplying the fuel, performing combustion, and treating ash with a solid fuel.

CONSTITUTION: An electronic control circuit automatically detects a water-full state in a water room, a temperature state, the operation of a motor, the drive of a blowing fan, and the like and performs control. After a new fuel is supplied and then the activation of a motor M is stopped, a sensor TS of a water room temperature detection part 34 detects a temperature in the water room W and applies a change voltage to an inversion terminal (-) of comparators OP1 and OP2, adjusts a temperature-setting resistor VR18, outputs a high-level signal, and inputs the signal to one terminal of an OR gate OR4 and an AND gate AND2 of a blowing machine drive part 36. Then, the output of a flip-flop circuit becomes a high-level signal, the signal is inputted to and AND3 and a power supply Vc flows to a resistor R21 and light-emitting diodes LED4 and LED5 for lighting them, thus reporting that a blowing fan 18 has been activated and hence, for example, efficiently using hot water and controlling heat.