PURPOSE: To prevent the internal pressure of a water tank from being influenced by the water head of solar heat collectors and consequently enable to relax restrictions on the installation height of the solar heat collectors by a method wherein the water circulating part in a hot water circuit can be kept in closed state at all times except in case of freezing at a water heater utilizing solar heat.
CONSTITUTION: In order to put the water heater utilizing solar heat into use, firstly, a solenoid valve 10 is open. Secondly, when the water level in a forward pipe 1a attains to the level predetermined under the pressure conditions set by a pressure-reducing valve 5, a circulating pump C is started and the air remaining within the forward and a return pipes 1a and 1b is discharged through a solenoid valve 3, which is open at this moment by means of a controller D. Thirdly, after that, when the water in a circulating circuit flows steadily and more than the set flow rate, a flow switch 2a is turned ON and consequently the automatic closing of the solenoid valve 3 is resulted by means of the controller D. The state as just described above establishes the formation of a closed circuit comprising the water tank B, the solar heat collectors A and the circulating pipe 1 and the pressure drop of the circulating pump C is caused only by the piping resistance and consequently the adoption of the pump C with smaller size than conventional one is possible.
TONARI MITSUHIRO
YOSHIDA MASATOSHI
KOBATA YUKIO
