Thanks for the information. If I find out anything then I will post it here.
The problem is it only occurs when the boiler has been heating for 5+ hours, so its rare that it happens. i am wondering if the problem has been there since it was installed 2 years ago.
I added a tube of...
Sorry to bother you, but did you ever get a resolution to the droning/humming on your main eco 30 Combi boiler? i have exactly the same issue with mine.
best regards
paul
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