Abstract: A passive circuit for protecting an AC driven load controlled by a solid state device such as a triac or the like. The circuit is coupled to the load and the solid state controller element and effects shutdown of the AC power to the load and the load control element whenever an asymmetrical AC power input measured over a predetermined number of cycles is received by the load from the controller element. The device includes an inductor having a thermal link coupled thereto, the inductor being connected in parallel to the AC load which is being controlled by a triac or other similar device. Should asymmetrical input power be received from the controller, which could be occasioned by failure of the controller element itself, the inductor across the load will become heated by asymmetrical input power, causing heating of the thermal link. At a predetermined temperature, the thermal link will open, which removes AC input power to both the load and the controller element.

Abstract: A flat plate collector of parallelepipedal configuration for a solar energy system, comprising a plane collective surface for the reception of solar energy with internal channels designed to maximize turbulent flow of heat-absorptive fluid therethrough and provide a maximum of heat absorptive surface in proportion to the volume of fluid content. As designed, the collector is adaptable to mass, low-cost production.