The boilers for the warm water production to + 95°C, have been expressly studied and constructed in order to use solid materials as fuel and alternatively gaseous and liquids fuels as well. The self-bearing sheet-steel structure consists of a great volume firebox with wet walls provided with a door openable at a walking pace for the manual loading of the material and for the periodic brazier cleaning. The horizontal heat exchanger with steel pipes dipped in the water to three smoke turns in order to obtain the maximum thermal efficiency and connected to the extremities to openable and inspectable smoke cases for the removal of the residual combustion products and for the periodic maintenance. The metallic bedplate is covered by a refractory pressing for high temperatures and laterally the walls are insulated by refractory elements which allow to obtain high temperatures for an optimal burning. In the bedplate is lodged the grill and the container for the ash collection if it works with a manual loading or the brazier if it works with automatic shaving feeding. All boilers have been supplied with bearing-plate for the application of the diesel oil or gas burner. The boilers are completely insulated with high insulating power rock wool mattress that is protected by steel oven-baked painted panellings. The automatic feeding is carried out with the (Fire)Fuocomatic made up of: shavings and/or briquettes feeding container provided with inner leaf spring and orthogonal motorreducer, helicoidal briquette miller with coaxial motoreducer, shaving carrying motorvariator with variable speed, spiral screw feeder, primary and secondary combustion air fan, water antifire device with thermostatic control. The boilers allow to satisfy the burning requirements using different kinds of solid fuels, having the possibility of optimal adjustments that together with the cyclones and multicyclones application allow to obtain workings in observance of the laws in force.