Noisy boiler - kettling?

[allotmentboss]

Hi,

I wonder if you can help.

Over the last few days my combi boiler (Ariston Genus 30) has started developing a noise whenever I draw domestic hot water. The noise builds up over about 30 seconds, starting out like the sound of a kettle starting to boil and ending up as a continuous loud low hum - like the sound of an articulated lorry braking heavily.

It doesn't make any unusual noises if we have just the central heating on. So,
Just central heating = quiet.
Just DHW = noisy
DHW + CH = noisy.

A month or so ago I did the following work on my system:
(1) Changed some piping for the bath's hot water. This is a long way from the boiler, and drawing water from any tap makes the noise. So, I believe this to be unrelated.
(2) Drained the CH system to fit a new radiator, and flushed it with desludging solution.

If this is "kettling", what's the best way to solve it?

Many thanks

[Oliver_murphy]

deslude and descale the system. Make sure its done properly.

[htg engineer]

It could just be the water to water / plate heat-exchanger is scaled up, you an remove the plate heat-ex flush and clean the ports etc.

Alternatively fit a new heat-ex but they're normally quite expensive.

Hope this helps