UFH TMV out of control

[Paul-c]

I have a problem with a new installed UFH system as follows.
One 46kW oil boiler heating two number 12 port manifolds plus DHW and rads and I am having difficulty controlling the TMV on both manifolds.
Having set both manifold mixing valves to around 45* the TMVs don't hold that temp.they both increase in value up to 55/60*
The floor temp probes are turning off the room stat. (protecting wood and tiled floor)
The fact this is on two seperate manifolds suggests the fault is not with an individual TMV
The common denominator is the boiler? or is there something else I have missed
Thanks
Paul C

 

[Darren Jackson]

The heads can easily be removed and put back on again in a different position giving a false temperature reading. You think it is set to your desired temp but more than likely it is actually higher than you think. It is best to remove the plastic head and adjust the valve without it use a pipe thermometer to get your temp right and then put the head back on the valve in the locked position if yours does that is.

 

[Chalked]

Are you sure your flow and return are correct way round?

 

[Paul-c]

The problem is that both TMVs is not holding the temp.
When set they both increase / decrease over time.
I have attached a photo of the pipework and checked that,
The cold water from the return (bottom) manifold is attached to the horizontal "C" port of the TMV with the opposite port attached to the boiler return pipe (rh copper pipe in the picture)
The hot flow from the boiler comes into the underside of the TMV
The pump flow arrow on the casing is in line with the flow of water going to the "hot" manifold
The manifold kit is supplied by underfloorheating1.co.uk
I have no manufacturer's name for the TMV
Have I missed anything?
Thanks
Paul

 

[Chriswareham]

you need to make sure you have the pipwork round the right way why is there no reading on the bar gauge it should be at 1.5 bar there may be air in the systerm so there will be spouts of hot water which will make the thermostat rize before the thermosatat shuts down

 

[Paul-c]

The TMV port fittings tend to make it fit the right way round plus the horizontal ports marked "C" being consistent with the return from the manifold going through the valve then return to the boiler.
The boiler pressure noted yesterday was 3/4 bar sothis was addressed but the boiler has never tripped with low pressure.
The system was well flushed out and has a filter in the return line.
Thanks