Underfloor heating issue - Hot Water Light off, system not heating

[MasterMark]

Well. Update. A heating engineer came in. He changed all the flow meters and one of the actuators that seemed like it might not be working. When removing all the actuators, he saw that the pin valves were almost all very close to being totally closed, so he turned them all on. On restarting the system, the 2 rooms/zones/floors that weren't heating started to get warm, so it looked like things were back to where I was. Great.

Woke up this morning and my bedroom was incredibly warm, even though the thermostat was off and the zone light in the manifold was also off.

Turning on the thermostat in one of the rooms that wasn't working (let's call it "The Study" - the zone in the manifold switches on, the floor heats up. Ok. But now all but one of the floors in the other rooms are also heating up, even though those thermostats are off and the zones do not appear to be activated on the actuators/manifold. How is that even possible?!

 

[Rodders53]

Back to the heating technician... something's wrong, and you have paid them to fix stuff.

Removing actuators usually causes the valve pins to rise up = to close the valve in most UFH manifolds. The opposite of TRVs where the pin is pressed in to stop flow.

The Actuators should, via the expansion of a wax insert that is heated electrically, operate the pin valve on the return manifold ... that moves from closed (no flow) to fully open slowly... it takes many seconds (minutes) to move the required mm or two.

If there is flow in a circuit (meter will show?) without the actuator calling then it's either mechanically stuck in the open (or part open) position or has (somehow) been mis-adjusted to effect the same. I believe the flow meters do something similar to adjust flow rate on the flow manifold side (in your install)?

Check the manifold flow meters!

 

[MasterMark]

Thanks Rodders! Heating engineer is now away for almost 2 weeks (he did tell mem bad luck for me).

I'm going to go zone by zone, valve by valve, flow meter by flow meter to see what happens when one is opened. But I seem to have a style of return pin valve that I can't see anywhere else (maybe what you were referring to about adjusting flow rate at the manifold?).

Pics attached - the pin itself doesn't seem to move on any of them. But they are threaded, and using a little plastic bleed piece, I can turn the pin so that it's fully exposed (no visible threads - assume that means valve closed?) or turned so that the threads "rise", with very little of the pin exposed (presumably valve open?). I THINK that when he came, these bits were all almost totally off (pin fully exposed), which he couldn't understand so opened them up almost fully).

Could it be something to do with these, such that having them now fully open means the actuators aren't doing anything and they're just permanently "on"?