Solar water heating system

A solar water heating system with forced circulation of the water which comprises, a water storage tank, a solar heater, piping system connecting the tank to the solar heater for flow of water between the tank and solar heater, a cold water inlet provided in the system, an electrical circuit connected to the system with power lines connecting the circuit to a source of power, a pump connected to said piping and to the electrical circuit to circulate the water in the piping when actuated by the electrical circuit, temperature sensing means connected to the piping system and to the electrical ciruit to sense the temperature of the water in the storage tank and electrically actuate the pump for circulation of water through the system within a normal preselected temperature range between the water in the tank and the water in the solar heater, first electrically operated valve means connected in the circuit to the temperature sensing means and actuated by the latter to stop operation of the pump when the temperature of the water in the solar heater rises above a preselected temperature range between the water in the storage tank and solar heater, additional electrically operated valve means connected to the electrical circuit and thereby to the sensing means and the pump and actuated by the temperature sensing means when the water in the solar heater drops to a selected low temperature to thereby stop operation of the pump and open the system to drain and shut off flow of water to the solar heater to prevent damage to the system by freezing, and the temperature sensing means including a solar heater temperature sensor connected at the water discharge end of the solar heater to sense the temperature of the solar heated water, a tank temperature sensor connected to the tank to sense the temperature of the water stored in the tank, and the first electrically operated valve means being a temperature differential relay electrically connected by the electrical circuit to the solar heater temperature sensor and the tank temperature sensor to open and close the circuit in accordance with the preselected differential in temperature in the solar heater relative to the temperature in the tank to limit the circulation of water to the tank from the solar heater within a desired temperature range.