Abstract: A solar hot water heating system, utilizing preferably a gas-liquid, phase change medium in the collector, employs one heating and storage tank above the collector and a preheating and storage tank below the first tank and preferably also below the collector. A cold water source feeds the inlet of the preheating tank which has its outlet connected to the inlet of the heating tank. The hot water outlet of the heating tank not only supplies heated water where needed but has a connection for recirculating surplus hot water to the inlet of the preheating tank by means of a pump which is activated and deactivated by a switch sensitive to the temperature of the medium.

Abstract: A heat exchanger-tank assembly is shown for use in a solar hot water heating system. Heat exchanger tubing extends between inlet and outlet manifolds defining downwardly sloping paths wherein the heat transfer medium may circulate. The heat exchanger is completely assembled outside a tank body and then installed therein. Inlet and outlet tubes protrude through suitable openings in the tank, one of which is defined by mating semi-circular cuts in an end cap and adjacent tank rim. Both horizontal and vertical tank embodiments are shown.

Abstract: Solar water heater using the phase-change principle including a collector, a condenser, and .[.an accumulator.]. .Iadd.a vapor release drum .Iaddend.joined to form a natural circulation system .[., including a pressure accumulator and a vapor release drum.]..Iadd.. .Iaddend.