Image Number 4 for United States Patent #6269808.
The period of pre-purging is selectively determined for improving the utility.When a main run switch is turned on, it is examined at S1 whether or not the temperature of the oil in a frypot measured with a thermal sensor is not higher than a first setting level. If the oil temperature is not higher than the first setting level, it is examined at S2 whether the post-combustion time exceeds 10 minutes or not. When the post-combustion time exceeds 10 minutes, the pre-purging is carried out at S3 for 80 seconds. When not, the pre-purging is performed at S4 for 5 seconds. Then, the combustion is commenced at S5.