The EBC-i inherits the high-precision air-ratio control function of the conventional EBC model, and yet succeeded in functional improvement including a great increase in the number of settable air-ratio patterns and availability for the cooling mode operation and thinned-out operation of the burner, with the adoption of a module-type controller. Furthermore, the EBC-i is provided with substantial touch monitor screens, thus making it possible to display up to 16 loops.