Can anyone please help. I have a Baxi boiler (not a combi). The first time it comes on in the morning for the water heater it make a grinding sound. It doesn't happen the rest of the day just the first time. A plumber has been out and changed the fan although he did not know what the cause actually was and hoped changing the fan would resolve it but it is still doing it. The noise is annoying but I am more concerned it is dangerous or about to pack in.