FORCED DRAFT COMBUSTION TYPE GAS WATER HEATER

摘要

PURPOSE:To stop the combustion of the titled water heater when abnormality of a servomotor is detected by a method wherein the combustion is stopped when the time set for a timer which operates at the time of energization of an air quantity controling servomotor and which is reset at the time of deenergization of same is up. CONSTITUTION:The temperature of hot water detected by a heat sensitive element 14 is compared to a set temperature by a proportional circuit and the difference between two temperatures is amplified to control the coil 12 of a gas proportional valve 10 and at the same time, it is inputted to a servo-circuit so as to be compared to the value of the opening degree of a damper 17 (at the air intake port of a fan 3) detected by potentiometer 19 whereby the opening degree of the damper 17 is adjusted by the servomotor 19. Further, a CR timer A is provided in an abnormality detecting circuit so that when the servomotor 19 is energized, a photo-diode is operated to make a photo-transistor conductive, the timer A is started when the transistor becomes non-conductive and when the supply of electric current to the servomotor 19 is not interrupted within a predetermined time, a comparator is reversed to generate a signal to a safety operation circuit after the predetermined time has lapsed, to thereby stop the combustion of the water heater.