| 摘要 |
PROBLEM TO BE SOLVED: To control combustion for a safe shutoff so that an abnormal combustion is not generated in the case of intake and exhaust paths are blocked up. SOLUTION: When a pressure loss has become great due to a blockage of intake/outlet paths and the like, a current-passage rate to a fan motor is reduced, and a predetermined number of revolution is maintained, in the above condition, when a load point calculated on the basis of a relation between the current-passage rate and a power source voltage is determined to be not in a combustion range for a satisfactory combustion, but to be a load point in a region in which an abnormal operation is possibly conducted due to insufficient air amount, then it is observed to determine whether such a state continues for a certain time or not, and if it continues, the pump drive is stopped to shut off the combustion to attain a safe and ensured operation.
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