UFH Thermostatic Mixing Valves

[John.g]

Are there fundamental differences in some of these TMVs?. The attached one, below, would seem to be the better type where a shuttle moves to balance the hot&cold flows, as it increases one flow it decreases the other to keep the mixed flow constant, necessary say in showers etc. I have seen comments where apparently some UFH TMVs just control the flow through the hot flow port to mix with the cold manifold returning water. In view that some have trouble with UFH & rads on together, ie rads being robbed of water by the UFH etc while others have no problems (both not using LLHs or CCTs) wonder if the type of TMV has a bearing on this?.

 

[John.g]

Finally got my hands yesterday on a TMV from a acquaintance many miles away who reckons it has a range of 30C/50C. This a anti-scal valve but the UFH ones will operate exactly the same way IMO. The adjustment screw has to be wound right back (anticlockwise) to ensure the piston valve seats properly and stops any cold water passing.
I hadn't fully understood how the thermostat operates but can see now that as it heats up the plunger in the top is (hydraulically) forced up against the adjusting screw which forces the piston valve downwards to allow cold water to mix with the hot or shut the hot off completely if required, say in the event of cold water supply failure.