Today our boiler kept tripping the RCD but with no fault code showing, and the engineer found the fault to be moisture around the area of the pcb. Once dry everything was fine. I've never seen this fault and he suggested it could have been rain ingress into the flue as last night was very wet & windy. A hairdryer sorted it! Does such a thing as a proper suitable flue cowl exist to prevent this happening again? If so could I fit it myself? Am experienced diyer.