Everything fires up quite normally. As the system warms up, the boiler makes a chuffing noise rather like a steam engine. When the operating temperature is reached,the noise generally stops, but will often start again intermittently when the boiler calls for heat. It only occurs while the burner is lit. The higher the boiler stat setting, the greater the problem. Any ideas.

Mike25., December 2010

its called "kettling" a comman problem with this boiler a standard inhibitor will probably cure it air gets trapped in the rough boiler casting causing minute localised hot spots

brian, December 2010