Hot/cold water flow differential

[terryplumb]

With cold flowing as well as hot ,what is the hot flow rate ( both open pipework)??
Putting aside the above for a moment,
when running the basin hot tap ONLY ,which you told us also runs at 6 lt/ min ,and no cold running , the boiler doesn't maintain constant temperature at that tap ? What explanation did the engineer offer with regard to that ??

 

[hotspot007]

He said pressure drop due to the height. He took me up to measure the flow at the shower with the mixer removed... To show me how the flow would be lower, when he measured the same he was surprised himself.
I kept on going back to 2 things. 1 - nothing has changed so why is it doing it now. And 2 - losing 3 liters a minute through the heating system seems a lot. It was then when we discussed the flow restrictor and he offered to take that off to check /clean/replace. He took it off and of course the housing broke - but tbf the restrictor was clear and clean. That was enough for him to then walk away and blame the water pressure. Its only after all this, and thinking about it - I'm still pulled to the plate heat exchanger. I'm not saying it is bad,im saying due to my low pressure/flow through the boiler - that it's only going to take a very small restriction to take the flow low enough for the boiler to then cycle - and due to the rise to the 2nd floor - that results in a fluctuation between hot and cold?
Just feel stuck.
Gas engineer blaming water pressure - and let's face it - it isn't the best. And water board sating it's great and again tbh they are not going to do anything about it with a standing pressure of 2bar and 9l/m flow.
Maybe I had a flow of 12l/m when I moved in - hence the boiler size fitted to a new build.

 

[hotspot007]

Just took some more measurements.
2 bar static pressure.
Dynamic pressure 0.8bar with cold tap in Bath fully open @15 litres a min.
0.1bar with bath and another cold tap open.
Static pressure at shower 2nd floor loft =1.3bar.
Dynamic pressure with shower running 8litres min combined = 1.4bar
Cold tap in kitchen 9 litres a min, hot 6 litres a min (both in sink and bath)