Solar heating system component

A solar heating system component comprising a closed vessel, a first fluid inlet and a first fluid outlet for said vessel, said first fluid inlet being adapted for connection to the fluid outlet of a solar energy collection system through which fluid flows in a closed system as a heat exchange medium, said first fluid outlet being adapted for connection to the fluid inlet of said solar energy collection system, said vessel defining an expansion tank for said solar energy collection system, a second fluid inlet and a second fluid outlet for said vessel, said second fluid inlet being adapted to receive a fluid to be heated, said second fluid outlet being adapted to forward such heated fluid to a point of use, and a heat exchange structure within the vessel positioned for heat exchange relationship to solar energy collector system fluid in the vessel, said heat exchange structure including means for fluid flow therethrough, said second fluid inlet and outlet being operably connected to said heat exchange structure, a first fluid pump connected to said first fluid outlet and a second fluid pump connected to said second fluid inlet for circulation of fluid through the respective systems, a first temperature sensor located to sense the temperature at the collector outlet, a second temperature sensor located to sense the temperature of fluid pumped by said second pump, a differential thermostat connected to said first and second sensors, means operably connecting said differential thermostat to said pumps to de-energize said pumps when the temperature of fluid being pumped by said second pump approaches the temperature of the fluid being pumped by said first pump, a pressure release valve for said vessel, and an air valve operable to close and open on said vessel located at a position above a selected level of solar energy collection system fluid to be present in said vessel to permit relief of air pressure in said vessel.