I have recently 3 weeks ago had an Alpha cdx25 fitted.
When the heating is on after a certain amount of time there is a loud water knock in the upstairs rads. I can stop this by turning on the hot water or shutting off or fully opening the rad thermostat to that rad.
The fitting engineer has returned and suggested that we have all thermostats changed on rads.
This never occurred in the old boiler. It has been suggested by a friend that the flow and returns are back to front.
This guy has told me he has fitted loads of these boilers with no fault.
He fitted one for a friend one week later and he has the same probs.
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