PURPOSE: To miniaturize the titled heater and to improve the efficiency thereof by a method wherein in the hot water heater incorporating a centrifugal hot air blower therein, tubular heat exchangers are arranged to surround the outer circumference of an impeller 1 within a casing for the blower and combustion chambers are provided in the tubes of the heat exchangers, respectively.

CONSTITUTION: The impeller 1 constituting the centrifugal blower is coupled to the rotary shaft of a motor 2, the casing 3 is provided around the impeller 1 and the two heat exchangers 4 are arranged along the inner surface of the casing 3. One end of each of the heat exchangers 4 is in communication with a burner chamber 5 and the other end thereof is in communication with an exhaust gas collecting chamber 6. In this case, the flow direction of a combustion gas in the heat exchangers 4 is same as the direction of rotation of the impeller 1 and a burner 19 is arranged on the upstream side of a diffuser in the casing 3 so that the combustion gas is discharged outside at a position adjacent the burner 19 through a discharge port 17 and a nose section 16 of the casing 3. As a consequence, the rate of heat transfer on the outer surface of each of the heat exchangers 4 in increased and no independent space for the heat exchangers is required.