Water temp from Megaflow initially very hot

[Johntheo5]

As post #9&14, ensure air bubble correct, it may be due to unbalanced hot/cold pressures even with a balanced cold as its upstream of the combination set NRV.
For example a 200L cylinder with a 65L bubble will have a final pressure of 4.0bar when heated to 60C, (from cold), assuming 3bar PRV setting then the hot/cold differential is only 1.0bar, now assume air bubble only 33L then the final pressure will be 5.6bar, and 2.2L of hot water must be drawn off before the pressure falls to 4.0bar??.

 

[CamberleyBaker]

Thanks for taking the time to post. I will arrange someone to take a look at doing this. I wonder if this is a common problem. Dates back almost a year to when I had our 2 boilers replaced and the installer added a 2nd expansion vessel to our system.