CHOTOSHIKIDENKIONSUIKINIOKERUKYUSUISUIONKENSHUTSUSOCHI

摘要

PURPOSE:To accurately control the heating by utilizing midnight power by a method wherein the minimum feed water temperature in a day is obtained by periodically bringing the feed water temperature in a hot water storage tank during the time when a heat generating body for midnight power is OFF. CONSTITUTION:When a midnight power heater 3 is turned OFF, a first comparator unit 10 brings the water temperature detected by a temperature sensor 7 in the cycle of mili-second order in order to obtain the minimum temperature in a day. A memory unit 11 stores the minimum temperatures obtained at the comparator unit 10 for the predetermined number of days and has memory areas M1-Mn corresponding to the predetermined number of days (n). A second comparator unit 12 brings the minimum values stored respectively in the memory areas M1-Mn in order to obtain the minimum value among the respective minimum values. An operational processing unit 13 calculates in order to obtain the operating hour of a midnight power heater 3 necessary for heating the water in a hot water storage tank 3 up to the required heating-up temperature under the condition that the minimum value obtained at the comparator 12 is employed as the feed water temperature. In addition, the energizing of the midnight power heater 3 is controlled through a relay 14 by the control signal corresponding to the result of the calculated operating hour of the heater 3.