thanks it always happens when both hot water and heating are on at the same time and when I turn the heating off via the controller it stops straight away, it's a 950x450 which was fitted approx 18months ago I would have to get back to you if you need the manufacturer?
I would appreciate if anyone could help as the engineer who installed the boiler is baffled by this noise which is intermittent but stops as soon as hot water cycle switched off on programmer. But no venting hot water from overflow, the stat on the cylinder has been changed etc
Can any one...