Abstract: A low NO.sub.x atmospheric gas burner is provided, which includes at least one burner tube having a plurality of gas outlet orifices terminating in a burner bed, and a plurality of plates disposed above the burner tube within the reach of the flame, which plates lower the temperature and effect a stepped combustion. According to the invention, the plates extend parallel to, and on opposite sides of, the orifices provided in the burner tube, and the orifices are arranged in a line parallel to the burner axis. The plates are connected direct to the burner tube substantially throughout the entire length of their lower edges.

Abstract: A heating boiler having a vertical, completely premixing burner tube arranged in a space shut off at the top includes concentrically relative to the burner tube a helical water tube surrounded by an upwardly extending flue gas discharge jacket. The burner tube comprises a lower circumferentially closed tubular mixing portion and an upper portion having burner ports formed by a plurality of stacked alternately flat and radially corrugated annular discs held together by a flat top plate connected through a bolt or the like to a cross piece or the like wedged in an internally tapered upper end of the circumferentially closed tubular mixing portion.

Abstract: Cast metal heat exchanger and mould therefor, in particular a fired central heating boiler operating on water or medium circulation, with two or more externally ribbed, hollow sections through which the water and about which the flue gases can flow, wherein the sections are cast integrally in sealed form at their end edges with sidewalls and end walls extending over the entire boiler length, except for the gas and water communication openings, on the side where the water and flue gas are present with respect to the outside atmosphere.