Wet UFH overheating - advice please

[Julesf]

We have a wet UFH system in an extension that has installed 10 years and we have had no issues with till now, there are 2 separate UFH systems and manifolds for upstairs and downstairs. We have gas CH with radiators in the rest of the house. Suddenly the UFH in the upstairs part is running super hot, its like a sauna in the room, temperature gauge/ dial near manifold was showing 60 degrees when downstairs its at 40 degrees max. We have 3 separate thermostats one for gas CH, one for down stairs UFH and one for upstairs UFH. The upstairs thermostat is set to same temperature as it always has been and display looks to be working as normal. We have turned down the boiler which has helped a little but now the CH part of the house is cold. Advice greatly appreciated as to where the problem may lie and if its a plumbing or electrical issue so we know who to call out. Thanks

 

[Leesparkykent]

Maybe the thermostatic blending valve is playing up on the manifold.

 

[ashrow]

+1 with the above response

 

[jackhammerJIM]

Sounds to me like the zone valve could be stuck open . Even if the blending valve is faulty and letting through 80C water from the boiler the room stat will close the circuit once temperature has been reached .

Consult a heating engineer competent in electrical controls or a sparky skilled in heating systems .