JPH0213221B

PURPOSE:To facilitate management of temperature of hot-water in a hot-water reserving tank by indicating under converting into the volume of hot-water diluted by water so as to obtain a temperature in accordance with a using purpose. CONSTITUTION:A total heat amount (a) with respect to an average temperature t( deg.C) in the hot- water reserving tank 1 is detected from the terminal of a sensor A as the output voltage V1 thereof. The total heat amount (b) in case the tank 1 is fully filled with supplemented water having a normal temperature T0( deg.C) is detected as the voltage V2, which is (n) times of the output voltage thereof when it is taken out of the terminal B of an element A1 near a water receiving port in case the element A1 is consisting of (n) pieces of temperature detecting elements having the same characteristic. Further, when a reference hot-water temperature upon bathing is 45 deg.C and the output voltage with respect to the total heat amount (c) in case the tank 1 is filled fully with the water having the reference temperature is V3, the following formula with respect to the relation of temperature-amount of hot-water can be replaced to the relation of heat amount-output voltage. Therefore, a formula; (a-b)/(c-b)=(V1-V2)/(V3-V2) is obtained and the volume X of the remaining hot-water converted into the reference temperature may be determined by multiplying it by the total capacity (d).