I have two wet central heating loops: one for the radiators, one for the underfloor heating. One these loops (the UFH loop) is not getting hot.
I have found where the two loops split and checked the automatic valves, both work as expected. I have checked both move when switched.
I have checked the UFH pipes, and flushed them through with new water to prove no blockages. I have bled the air the UFH manifold as well as all the radiators. I have left it running for 48hrs to be sure it isn't something that just takes time to settle. I have checked the pump for the UFH, and that is spinning well. I have checked the UFH mixing valve, and that appears to work, and if I set it to fully cold, the flow rate can be seen on the manifold that water is being pumped round my UFH pipes.
I have run out of things to look at which could be the cause.
What else should I check?
UPDATE: I have replaced the mixing/bypass valve to ensure it isn't that which is broken. Still same behaviour.