Shower Temp too high / pressure low after installing unvented system how to resolve?

[wigwam12]

HI All
We switched from a gravity fed system in the loft where we had shower pumps feeding both bathrooms (it took an age to get hot water to the downstairs taps)
to a system boiler and unvented hot water system downstairs
Pressure out of the taps is decent (better than before tbf) the issue is the showers:
1. The biggest problem is they run too hot even on "tepid" settings (we have Grohe Thermostatic bars on both - unchanged) and sometimes in the shower the water can suddenly become too hot to the point of scalding - even turning it to full cold takes a while to being it down when this happens
2. It takes a few minutes now to get hot water to the showers (reverse of kitchen tap scenario) which I am assuming is related to too-small taps between upstairs and down somewhere?
3. The pressure is quite low - servicable as a shower and yes I know we don't have a pump anymore but subjectively feels like it is lower than coming out of the taps even the adjacent bathroom sink/bath taps

The main concern is the unstable hot water as we have all been scalded at some point and the little one no longer enjoys showering because of this
Feels to my mind we have a hot/cold balance somewhere to the showers? How would we resolve this please?

 

[Johntheo5]

Can you post a picture of your unvented installation showing the cold feed in with reducing valve set etc, also expansion vessel, if installed, what make/model UV cylinder?

 

[wigwam12]

Can you post a picture of your unvented installation showing the cold feed in with reducing valve set etc, also expansion vessel, if installed, what make/model UV cylinder?

Hi

Not sure which the reducing valves are
There is an expansion vessel
I've just taken pix all around hoping that gives the information

 

[Johntheo5]

OK thanks,
Can you see if there is any other pipe apart from the ones marked 1,2&3 on that valve set, (I don't think there is) also, what is written on top of the grey pressure reducing valve and the blue expansion relief valve (both arrowed), may be 3bar & 6bar.

 

[wigwam12]

I don't see any other pipes on that valveset
As you said grey says 3 Bar, Blue says 6 Bar (pic)

Away from the boiler/tank are this valveset but they are from the old set up and on/off I think?

Btw on my setup the CH is controlled by Hive but we keep the water (heating) on constantly on basis that it is thermostatic controlled and the tanks are well insulated so don't drop temp / call on the boiler unless needed (probably not relevant these last few points but I thought I'd mention

 

[Johntheo5]

Generally but not allways there is another pipe taken off that valve set just after the pressure reducing valve, this is called the balanced cold and will be at the same pressure (3bar) (or lower) as the hot water coming from the cylinder, if not a balanced cold then the cold may/should have another pressure reducing valve set to 3bar, I know you are getting scalding hot water but if there is another separate pressure reducing valve on the cold somewhere it might be causing your problem, try and see, or get someone to see, if there is, your installer should know.

"Away from the boiler/tank are this valveset but they are from the old set up and on/off I think?" These are the motorized zone valves from the boiler for heating the HW Cylinder & the CH, rads etc.

 

[wigwam12]

I'll ask the installer and feed back
Many thanks