| 摘要 |
PROBLEM TO BE SOLVED: To remarkably reduce usage of an electric heater by heating a heating tool for vaporization to vaporize liquid fuel by pre-heat combustion. SOLUTION: A burner head 17 consists of a preheat burner head 18 to heat the heat receiving part of a beating tool 5 for vaporization, and a main burner head 19. A primary air passage connected to a burner head 17 from a fan 16 through a vaporization 13 is branched from a position situated downstream from the vaporizer 13 and connected to the preheat burner head 18 and the main burner head 19. A vaporizer damper 23 is situated at the branch part. This constitution heats the heating tool 5 for vaporization by an electric heater 12 to vaporize liquid fuel 10 during starting of operation, and after starting of combustion, a vaporization surface 7 of the heating tool 5 for vaporization is heated to temperature, at which liquid fuel is vaporized, by the preheat burner head 18. A heat-exchanger 25 is heated by the main burner head 19, and after starting combustion, heating of the heating tool 5 for vaporization by the electric heater 12 is hardly needed.
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