A combustion appliance for solid fuels, comprising a support framing in which are contained: - a combustion chamber; - means for conveying combustion air from the outside to said combustion chamber, said conveying means comprising an inlet mouth of said combustion air; - a heat exchange group comprising a duct of the fluid to be heated and a combustion smoke duct, said ducts (81, 82) being separate from each other and thermally cooperating; each of said ducts (81, 82) having an outlet mouth (81b, 82b); said support framing defining a shape provided with a front face, a rear face opposite to said front face, a lower base and an upper part opposite to said lower base; said lower base being adapted to be arranged parallel to the horizontal plane on which a first horizontal direction parallel to said front face and a second horizontal direction orthogonal to said front face are defined; the appliance comprising at least one outlet group associated with at least one of said outlet mouths (81b, 82b) and contained in said support framing, said outlet group comprising: - a flange coupled to said outlet mouth (81b, 82b); characterized in that the outlet group further comprises: - a manifold element with a tubular through shape having an inlet port provided with a counter-flange adapted to be removably fixed to a first surface of said flange and an outlet port, opposite to said inlet port, adapted to be associated with an external pipe; said manifold element being shaped in such a way that it can be fixed to said flange according to at least three mutual positions so that said outlet port is arranged according to at least three distinct orientations corresponding to: - a first orientation, in which the plane (δ) on which said outlet port lies is substantially horizontal; - a second orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said first horizontal direction; - a third orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said second horizontal direction. - a combustion chamber; - means for conveying combustion air from the outside to said combustion chamber, said conveying means comprising an inlet mouth of said combustion air; - a heat exchange group comprising a duct of the fluid to be heated and a combustion smoke duct, said ducts (81, 82) being separate from each other and thermally cooperating; each of said ducts (81, 82) having an outlet mouth (81b, 82b); said support framing defining a shape provided with a front face, a rear face opposite to said front face, a lower base and an upper part opposite to said lower base; said lower base being adapted to be arranged parallel to the horizontal plane on which a first horizontal direction parallel to said front face and a second horizontal direction orthogonal to said front face are defined; the appliance comprising at least one outlet group associated with at least one of said outlet mouths (81b, 82b) and contained in said support framing, said outlet group comprising: - a flange coupled to said outlet mouth (81b, 82b); - a flange coupled to said outlet mouth (81b, 82b); characterized in that the outlet group further comprises: - a manifold element with a tubular through shape having an inlet port provided with a counter-flange adapted to be removably fixed to a first surface of said flange and an outlet port, opposite to said inlet port, adapted to be associated with an external pipe; said manifold element being shaped in such a way that it can be fixed to said flange according to at least three mutual positions so that said outlet port is arranged according to at least three distinct orientations corresponding to: - a first orientation, in which the plane (δ) on which said outlet port lies is substantially horizontal; - a second orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said first horizontal direction; - a third orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said second horizontal direction. - a manifold element with a tubular through shape having an inlet port provided with a counter-flange adapted to be removably fixed to a first surface of said flange and an outlet port, opposite to said inlet port, adapted to be associated with an external pipe; said manifold element being shaped in such a way that it can be fixed to said flange according to at least three mutual positions so that said outlet port is arranged according to at least three distinct orientations corresponding to: - a first orientation, in which the plane (δ) on which said outlet port lies is substantially horizontal; - a second orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said first horizontal direction; - a third orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said second horizontal direction. - a first orientation, in which the plane (δ) on which said outlet port lies is substantially horizontal; - a second orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said first horizontal direction; - a third orientation, in which the plane (δ) on which said outlet port lies is substantially vertical and parallel to said second horizontal direction.