I have an 18 month old Viessman Vitodens 100 Combi Boiler.
Recently it seems that the hot water coming ouyt of the taps is coooler than it used to be.
With the hot tap running and the heating off: Checking the display on the front of the boiler claims the burner is on full and that the output temperature is about 70 degrees. But water temp at tap is about 45 degrees. I am sure it used to be hotter (But I have no figures from then - I did not measure it)
Turning the boiler control up to maximum does not increase this any further (it is doing as much as it can already)
I can get the water at the tap a little hotter by reducing the flow a small amount. But reducing any further and the boiler cuts down the power, so I just get less water at the same, somewhat low temperature.
Question: Is this a common fault in Combis (my first). What is causing it?