Abstract: A proportional combustion control device for supplying fuel to a combustor for a boiler, a hot water maker, etc., comprising an opening and closing valve for controlling a supply of fuel provided in the midst of a fuel supply pipe, and a control valve having a spindle whose needle portion at the extreme end is moved in and out of a nozzle and an exciting coil to generate a drive force for intermittently and axially moving said spindle against the restoring force by being supplied with a drive pulse, wherein even if fuel is either oil or gas, proportional control of combustion can be made, and the spindle is intermittently moved in the range capable of continuously carrying out combustion to open and close the nozzle whereby jetting of fuel is subjected to proportional control at the turndown ratio of 1/5 to 1/10 to always render the stabilized combustion possible.

Abstract: A combustion control device capable of detecting a self-discharge state caused by a failure of an ultraviolet ray detecting tube by interrupting flames from a combustion mechanism to an ultraviolet ray detecting tube by opening and closing a shutter, integrating, by an integrating circuit, detection signals from this ultraviolet ray detecting tube only when the shutter is closed, comparing the result of this integration with a preset judgement level by use of a first judgement circuit, and determining a failure by comparing a result of this comparison with a preset failure judgement frequency by use of a second judgement circuit, thereby improving maintainability.