Patent ID: 8535050
Filing Date: 2013-09-17
Classification: F23N

Abstract:
1. A forced flue type combustion device which has a combustion chamber incorporating a burner, an air supply passage for supplying combustion air to the interior of the combustion chamber, an exhaust passage for discharging flue gas in the combustion chamber generated by combustion with a burner, and a combustion fan interposed in one of the air supply passage and the exhaust passage, and in which combustion air is forcibly supplied to the interior of the combustion chamber by the rotation of the combustion fan, while flue gas in the combustion chamber is forcibly exhausted out of the combustion chamber by the rotation of the combustion fan, the combustion device comprising: an orifice provided in at least one of the air supply passage and the exhaust passage; a pressure difference sensor for detecting the difference between the gas pressure on the upstream side of the orifice and the gas pressure on the downstream side of the orifice; clogging determination elements configured to determine whether a clog exists in at least any one of the air supply passage and the exhaust passage on the basis of a detected pressure difference value from the pressure difference sensor; and determination control elements configured to control the execution of determination by the clogging determination elements, wherein during weak combustion in which the combustion fan rotates at a rotational speed equal to or lower than a first predetermined speed, the determination control elements are arranged to execute a first processing for a first predetermined period of time and a second processing for a second predetermined period of time longer than the first predetermined period of time, the first and second processing being performed alternately and repeatedly and to execute the determination by the clogging determination in an interval on or after the first processing is executed and before the second processing is executed, wherein during weak combustion, the burner burns at a combustion rate lower than a predetermined value, and wherein the first processing includes a processing to increase the rotational speed of the combustion fan from the first predetermined speed to a second predetermined speed higher than the first predetermined speed and thereafter maintain the rotational speed of the combustion fan at the second predetermined speed, and the second processing includes a processing to decrease the rotational speed of the combustion fan from the second predetermined speed to the first predetermined speed and thereafter maintain the rotational speed of the combustion fan at the first predetermined speed.