Cast metal heat exchanger and method of formation

Claim 1

A cast metal heat exchanger in combination with a hot water boiler having a fuel burner from which hot exhaust gases rise and pass in thermal engagement through the heat exchanger, the heat exchanger comprising: a plurality of substantiallly cuboid cast metal waterway sections, each of the waterway sections having a cuboid volume not greater than 4,500 mls.; the waterway sections being interconnected at spaced intervals so as to define unobstructed and substantially cuboid flueways therebetween; the heat exchanger and the individual waterway sections and flueways being rectangular when viewed in plan, transverse to the direction of movement of the hot rising exhaust gases, the major axes of the viewed rectangles of the individual waterway sections and flueways being disposed parallel to the minor axis of the viewed rectangle of the heat exchanger; and, walls of the cast metal waterway sections forming a majority of primary heat exchange surfaces having a thickness not greater than 4 mms., whereby more efficient transmission of thermal energy from the hot gases to water flowing through the heat exchanger can be achieved notwithstanding the small size and volume of the heat exchanger.