Separable combination boiler

A separable combination boiler comprising a boiler body including:

• at least two horizontally aligned cylindrical boiler units each of which has in each end wall a central opening and a gas port above the central opening for the passage of combustion gases, and a front cover plate and a rear cover plate which are laid over the central opening in the front end wall of the foremost boiler unit and the central opening in the rear end wall of the rearmost boiler unit respectively, said boiler units and front and rear cover plates being separably joined together by fastening means provided thereon;
• a heat exchanger contained within said boiler body and divided by said boiler units into an equal number of heat exchanging elements which are interconnected by tubes to allow an uninterrupted flow of heat-transfer medium therethrough;
• a burner mounted on said front cover plate with its flame spout extending through a central opening in the front cover plate and the central opening in the front end wall of the foremost boiler unit;
• a stack mounted on said boiler body and communicating with an exhaust port formed in one of said cover plates which faces the end of a combustion gas passage defined by said boiler body and heat exchanger;
• wherein each heat exchanging element is constructed of at least one inner cylinder serving as a combustion chamber and one outer cylinder which are concentrically arranged within each boiler unit and spaced apart from each other by a helical plate surrounding the inner cylinder so as to form therebetween a helical passage for combustion gases, said helical passage extending from the gas port in one end wall of the boiler unit to the gas port in the other end wall thereof.