| 摘要 |
PROBLEM TO BE SOLVED: To perform further accurate computation of an amount of remaining water by utilizing system efficiency by a method wherein respective system efficiency corresponding to the temperature of hot water returned through a return pipe is computed from an amount of pouring water, a quantity of charged heat, and an increasing temperature and the system efficiency corresponding thereto is stored. SOLUTION: In addition to a control device 45, a memory device 46 is mounted on an electrical board 41, and memory is effected throughout a range of a state where no water remains to a reference amount of water at a time when water is poured up to a level above that of the circulation metal fitting of a bath tub. Additional boiling operation is effected in a reference amount of water state and each time a given temperature is increased, system efficiency corresponding to the temperature of current return hot water is determined through computation, and a table value therefor is stored at a memory device 46. Thus, during operation to automatically fill with hot water starting from a following state that remaining water is present, from a table of system efficiency stored at the memory device 46, system efficiency corresponding to the temperature of return hot water during computation is selected and by utilizing the efficiency, an amount of remaining water is calculable, whereby a further accurate amount of remaining water is determined. |
