problem with hot water - vaillant ecomax 242/2e?

Common problem with most combi boilers at this time of year. The outside water temp is much lower than in the summer and the boiler has to work harder to heat this to the same temp that it usually does. So as you have said you have to turn down the water flow rate, that is what most of us have to do at this time of year.
If the problem is really bad then get a CORGI engineer to check the burner pressure it may be too low.

Stewiesnake
November 2008