It was gas rated when it was fitted, and nothing has changed, flame burning really well, nice and blue, looks like it always has been. Anyway that wouldn't explain why the temperature control system was turning the boiler off, would it?
This boiler is a heat only system. Started last year not getting the rads anyware near as warm as usual, although it has been fine for several years running at about 5 on the boiler control setting. Fixed a clip on thermometer onto flow pipe from boiler, and only read 60ish Deg. Should be...