| 摘要 |
A main burner 22, a pilot burner 25, and a lead-in pipe 29 supplying combustion exhaust to the pilot burner 25 are arranged in a combustion chamber R2. A flame arrester 27 with small holes 27a is provided at a bottom plate 13. Furthermore, a primary thermocouple 26 detecting the flame state of the pilot burner 25 and a secondary thermocouple 28 detecting the temperature in the combustion chamber R2 are connected in series but with opposite polarities. When the flame arrester 27 clogs up with fine particles, the pilot burner 25, which sucks in combustion exhaust, performs abnormal combustion before the main burner 22, which is detected by the primary thermocouple 26 and the secondary thermocouple 28, whereupon the combustion with the main burner 22 is stopped. Thus, incomplete combustion due to blocking of the air supply path can be prevented.
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