| 摘要 |
PURPOSE:To maintain the gas supply volume and air supply volume always in a suitable relation by opening a proportional valve to an opening degree that is corrected on the basis of the actual rotational speed of a combustion air supply fan. CONSTITUTION:A central process unit 20 sets up the target opening of a proportional valve 11 after calculation based on a required heat quantity, and at the same time this target opening is compared with air volume data and adds to the target opening an amount of correction corresponding to the result of comparison, sends out the proportional valve opening output signal to a proportional valve opening output circuit 25 and drives a fan motor 16, a proportional valve 11 at a suitable speed and a suitable opening respectively. Namely, the speed of response of the proportional valve 11 is approximately matches the response speed of the fan motor 16. With this arrangement, even if the hot water supply temperature is changed abruptly, the gas volume and air volume can keep a suitable relation, and none of yellow flame phenomenon and of lift combustion occurs. |
