(under subclass 412) Subject matter having a circulating conduit communicating with a boiler at the water level, having a mechanical pump in the circuit for withdrawing water from the boiler at the water line and returning it to the boiler at some other point and having means for heating the feed water by means of either the surface or jet type and injecting the feed water into the boiler or conduit, but so arranged that the water level in the boiler will be maintained.
SEE OR SEARCH THIS CLASS, SUBCLASS:
398, 402, 403, and 406, for combinations of circulating pump with boiler.
