Abstract: A water-tube boiler is disclosed, comprising a body in which are located the furnace and a series of vertical tubes serving as heating and exchange surface between the furnace and the water to be heated flowing through these tubes, two respectively upper and lower manifolds to which the tubes are connected, and further comprising two independent water flows, one through the upper manifold to which the outgoing and return ducts of the heating circuits are connected, the other caused by thermosiphon action inside the tubes and the upper and lower manifolds.

Abstract: Gas-burning boilers have in a chamber a plurality of finned heat-exchange tubes arranged around a central gas burner which is substantially of the same length as the finned tubes. An extraction fan draws gases from the chamber such that the chamber works under sub-atmospheric pressure which is preferably 12 mm water column or more below atmospheric.Baffles provide that hot gases must pass over the heat-exchange tubes as they go from the burner to the fan. A self-operating pressure regulator may be provided for the chamber, and various advantages constructions of burner are disclosed which give silent and evenly distributed burning of the gases. The burner is arranged on a horizontal axis and so as to be withdrawable as a unit from the chamber without affecting the heat-exchanger tubes or baffle arrangements.