HOT WATER HEATING DEVICE

PURPOSE:To enable a start up to a preset temperature promptly and moreover eliminate a large overshoot by carrying out forced combustion at the maximum power in the initial rise time, reducing the quantity of gas gradually when the temperature of discharged hot water becomes lower than a preset temperature, and transferring the operation to PID control when a specified quantity of gas is available. CONSTITUTION:During a rise time a forced combustion circuit 12 operates and outputs a signal so that a proportional valve 9 may be opened to a maximum. A burner 8 heats a heat exchanger 1 with the maximum power. Therefore, the temperature of discharged hot water rises at the maximum inclination. When the temperature of discharged hot water becomes a specified temperature (for example 75 deg.C) lower than a preset temperature (for example 80 deg.C), a subtraction circuit 13 operates and the data of gas quantity output to the proportional valve 9 is subtracted per specified quantity. The quantity of subtraction at that time is properly calculated in accordance with the temperature of discharged hot water and further forced combustion time and decided. When the subtraction is repeated and the reduced gas quantity reaches the specified value, this value is replaced as an integration initial value of PID control; then DIP control starts.