Kettling

[lindleyj]

I have a Potterton Lynx combi boiler about 12 years old which makes hell of a noise which I think is kettling . I have bled all the radiators and I am not sure what else I can do . This just on the central heating not the hot warter , the radiators are amazingly hot. Any ideas

 

[ChrisR]

Scale is causing the noise. You could try a Boiler Silencer, or a Boiler Descaler, or get a £300 powerflush done. The first 2 are liquids you'll get from a plumbers merchant.
I wouldn't be terribly optimistic , success stories are rare, though you may get some improvement. Old boiler but not too bad a design, until the auto air vent leaks and gets the electrics wet.

Hot rads - cant remember if there's a knob to turn it down, but I do remember there's an undocumented adjuster on the pcb to reduce the output on heating. Most installations don't want 80,000 Btu/hr.

 

[lindleyj]

Is it possible that there is air in the system. During the summer I had to take a rad out to decorate and used the drain valve downstairs. In the morning my wife said that the central heating had been gurgling all night which was explained by the fact that I hadn't shut the drain plug properly and we had a wet carpet, so it is possible that it got a bit emptier than I meant it to.
Turning the thermostat on the boiler from max to min for the central heating doesn't seem to make much difference to the temperature of the radiators whereas it does on the hot water side.