Many thanks for your response. Have discovered that cold feed and expansion pipes are partially blocked (used powerful magnet). Work being done next week.
The burner door was removed and scale removed using a nylon brush with a mixture of strong white vinegar and limescale remover. All surfaces were smooth and scale free when the door was replaced. Now running Fernox F3 through the system for a week.
Many thanks
Tony
Hello, I've recently experienced a problem with the above boiler. Boiler is 10 years old and has become noisy. Gas engineer put Fernox F2 boiler silencer into system. This exposed a noise which sounds like drums being played inside the boiler! This only occurs when the boiler is fully surging in...