Pressure balancing device for heating systems

Claim 1

A pressure balancing device for use in a heating system employing therein a heating medium, said device comprising: an expansion tank adapted to be connected to said heating system and having separate feed and drain pipe means connected thereto for respectively feeding said heating medium to said expansion tank from said heating system and draining said heating medium from said expansion tank to said heating system; said expansion tank having therein first chamber means, fluid isolated from the exterior atmosphere, for storage of said heating medium received from said heating system, said first chamber means being maintained at a pressure lower than that of said heating system; second chamber means, having an interior in communication with the exterior atmosphere and an exterior exposed to the pressure in said first chamber means, for varying the volume of said first chamber means dependent upon the pressure therein; valve means, positioned in said feed pipe means, for normally closing said feed pipe means and for opening said feed pipe means upon an increase in pressure in said heating system to thereby pass said heating medium from said heating system to said first chamber means; and pump means, positioned in said drain pipe means, for normally closing said drain pipe means and for opening said drain pipe means upon a decrease in pressure in said heating system to thereby pump said heating medium from said first chamber means to said heating system.