Just finished the boiler side of changes (shunt pump circuit)
Background (skip if familiar with thermal stores)
The DHW is drawn off via a heat exchanger at top of the store via a TMV, it is fed by mains water - hence mains pressure DHW ... big benefit. Should you want to it is also drinkable.
The UFH system has a 28mm loop connecting manifolds to a lower heat exchanger in the store. There is no mixing valve (or any control) of UFH loop temp, other than by the store stat which is set to 60 degrees.
Each zone has its own digital stat which actuates the floor lop at the manifolds.
At end of last year I added a PV array on my roof, as well as being paid for all you generate, any you use is free. You try to use washing machine, dishwasher etc., but still leaves a lot of generated power being exported that you could use and still be paid for it. To that end fitted a solar diverter switch that dumps any unused generated power into the immersion
Added complication is that to get continuous DHW you need to stir the store (De-stratify), in normal use the boiler pump is used for this, flow switch detects any DHW draw off.
I have added a shunt pump circuit as shown in attached diag which will provide the de-stratification when boiler is off. Initially will simply switch off in summer - although assume I will add a programmer (1day 1ch) to allow me to switch back to boiler once a day then if there has not been enough heat input from PV boiler can top-up so plenty of DHW in morning for showers.
To allow me to run store hotter (use more of my PV energy), I need to install a TMV to ensure the UFH loop cannot exceed 60 degrees.
That is what is shown in the 2nd diagram above.
So I need to fix a TMV to the store connections ......... so started looking around for suitable 28mm valve, and came across this one:
This may be eminently suitable, however it was the text that says that normal TMV2 valves would not be suitable as they cannot work continuously at high temperature. Is this correct, or some hype (my get that valve anyway as price s reasonable)
Secondly anybody care to recommend a good non-ferrous 28mm TMV ?