Vaillant Ecotec boiler. Installed december 2008, under 1 year old. My plumber has been out a few times, Vaillant have sent their engineer out once, coming back next week again. Problem is intermittant, sounds like comiong from inside boiler, more like a rattle. I did think it was air kettling inside the boiler, both my plumber & Vaillant engineer said this isnt the case. The noise used to be much more of a howl, but the Vaillant engineer turned the gas flow down a lot on his last visit, so now takes much longer to heat up, and howl has turned into a knocking. Will post up again if i ever find out the cause Vaillant engineer been out, reckoned noise was kettling, either air or debris in heat exchanger. Said its not a boiler problem as such, therefore nothing will be done under warranty. Did turn thermostat down to 65, and that has cured it as not runni ng up to full temp. Had it serviced today (dec 2009), my plumber agress its probably debris in the heat exchanger. We are going to clean and totally flush system, if that doesnt cure it i will get Vaillant back again to (hopefully) clean or replace heat exchanger)
