CONTROLLER FOR WATER HEATER

摘要

PROBLEM TO BE SOLVED: To provide a controller for a water heater having a self diagnosis function for detecting the blocking degree of a heat exchanger without fault to make an appropriate decision. SOLUTION: An indicator voltage measuring means 16 measures a fan indicator voltage output when a revolution speed control means 14 controls a combustion fan 3 at a fixed number of revolutions, while a correcting means 13 corrects the fan indicator voltage by converting the same to that under a standard fan power voltage. At that time, the correction is made based on a fan power voltage measured by a power monitoring means 12 according to a characteristic equation expressing a relation between the fan power voltage and the fan indicator voltage. Converting the fan indicator voltage to that under the same fan power voltage eliminates the influence of fan power voltage fluctuation. A self diagnosis means 17 detects a change with time in the fan indicator voltage based on a difference between an initial fan indicator voltage measured and corrected at the early stage of installation of the water heater and the fan indicator voltage measured and corrected at the present moment to stop the water heater in response to a change exceeding a predetermined value.