Abstract: A control system for selectively regulating the operation of water heating tank in accordance with anticipated hot water demand thus eliminating storage heat losses during periods when hot water is not required includes a remote control unit, a relay unit and first and second thermostats, all electrically connected selected circuits with an electric heating element located within the tank. The first and second thermostats are arranged to sense the temperature of the tank water and the operating temperature (115.degree. F.) of the first thermostat is lower than that of the second thermostat (150.degree. F.). The remote control unit includes a three-position switch in circuit with the relay unit and first and second thermostats to permit continuous energization of the heating element under control of either the first thermostat in the first switch position or the second thermostat in the second position to provide a continuous supply of hot water at either 115.degree. F. or 150.degree. F.

Abstract: A solar collector system wherein water is continuously circulated between collector units and a reservoir and the conduits between the reservoir and the collector units are free of valves and like restrictions for enabling full drainage of the system when water is not being pumped through the system. Circulation is established by an initially operating large capacity pump to charge the system with water, and a small capacity pump takes over the maintain circulation after the system is charged, pump operation being controlled by the temperature of water in the system heated by the sun.