Differential temperature controller for use in a solar energy conversion

Abstract

An integrated circuit dc-comparator compares voltage signals representative of sump water and collector water temperatures in a solar energy conversion system and continuously provides a direct current voltage signal from the time that it is sensed that the collector water is 11.degree. F warmer than the sump water, until such time as it is sensed that the collector water is only 2.degree. F warmer than the sump water. The integrated circuit is latched to provide the continuous dc signal notwithstanding variations in noise level, by a resistor connected between the integrated circuit output terminal and the integrated circuit input terminal at which the collector water temperature is sensed. The direct current voltage signal gates-on a sensitive gate thyristor which in turn provides a gating signal to a high power thyristor connected in cascade therewith to enable the high power thyristor to energize a pump motor for pumping water between the solar energy system collector and sump until a temperature difference of only 2.degree. F between the collector water and sump water temperatures is sensed. The integrated circuit may be inhibited from providing the direct current voltage signal for enabling the pump motor whenever the sump water temperature exceeds a certain upper limit notwithstanding the difference between the sump water and collector water temperatures.