LIQUID HEATING DEVICE

PURPOSE:To improve the thermal efficiency by directly supplying hot gas from a cutout in the guide member to the hot gas passage segment opposite to the exhaust gas line inlet without passing through the upper wall of the heat transmission section. CONSTITUTION:A hot gas passage 7 is formed in the interior space 3 of the heating surfaces 2a, 2b over the entire length between the guide member 6 and the circumferential wall 2a of the heat transmission sections 2a, 2b. An exhaust gas passage 8 is connected to the underside of a part of the hot gas passage 7, and a cutout 9 is formed in the guide member 6 opposite to the inlet 8a of the exhaust gas passage 8 to allow the hot gas to flow from inside the guide member 5 to the circumferential wall 2b of the heat transmission sections 2a, 2b so that the adverse effect by draft in the exhaust gas passage 8 may be sufficiently controlled and the hot gas may be sufficiently supplied to the entire part of the hot gas passage 7 so as to allow the hot gas to come in contact with the entire circumferential wall 2b.