JPS6244186B

PURPOSE:To enable miniaturization of a circulation pump, by a method wherein a diameter of a return pipe of a heat collecting circuit is made smaller than that of a feed pipe so that an air breather in a heat collecting circuit in the beginning of heat collecting operation can be used easily. CONSTITUTION:A solar heat collector 1 and an open air type heat accumulator 2 are connected by a feed pipe 6 and a return pipe 7 with each other, a circulation pump 8 is provided on the feed pipe 6, and water supply devices 3 and 4 which supply water into the heat accumulator 2 are provided further. A low temperature actuation valve 10 which releases at a fixed temperature is provided on the top part of a heat collecting circuit consisting of the heat collecter 1, the feed pipe 6 and the return pipe 7 and the diameter of the return pipe 7 is made larger than that of the feed pipe 6 so that air is taken in the above heat collecting circuit from the valve 10 at the above fixed temperature. Ventilation of the inside of the heat collecting circuit in the beginning of heat collecting operation is facilitated and miniaturization of the circulation 8 is made possible as the diameter of the return pipe 7 is made smaller than that of the feed pipe 6, that is.