nickldn

I did some testing this morning and not much luck. The gauge continues to show the flow temperature from the boiler, no matter how the dial below it is set. Tomorrow I'll set the dial to minimum and set the flow temperature to 60 degrees. If the floor warms up a lot then I will know the blending valve doesn't work. Thank you for your help. I feel that I understand how this is supposed to work now.

So just to be totally clear does your gauge at the top show the blended water temperature, so when you turn your blending valve clockwise the temperature reduces? Or does it show the flow temperature from the boiler before it's been blended? Sorry for being dense here.

Thanks for your replies. I have uploaded a zoomed out photo, the pipe with the blue valve motor box on it is the flow from the combi boiler. The return is the pipe next to it with the red earthing tag. If I get water at 60 degrees from the boiler, it remains at 60 degrees in the upper (red) part of the manifold, which gets very warm to the touch. The bottom (blue) part of the manifold stays much cooler (but is still warm to the touch of course). Gauge does read ambient after some time and matches flow temperature from boiler accurately, so I think it's fine. Having read your helpful comments am I right in thinking the dial adjusts the return temperature, so I should expect to the top (red) part of the manifold to be the same temperature as the boiler flow and the bottom (blue) part to be the temp of the actual water going through the UFH? If so that's what's happening I think.

My UFH was installed about 5 years ago and runs from a Vaillant combi boiler. One issue I have never been able to sort out is the water temperature adjustment for the UFH. There is a valve to control the UFH water temperature by blending hot water from the combi with cooler water from the UFH pipework. But it doesn't seem to work, floor gets very hot if the boiler flow temperature is set high. When I set the dial on the UFH to 45 degrees, the temp indicator above the pump matches the boiler flow water temp. Picture shows almost 60 degrees, which is too much. As a workaround I turn the combi temp down to about 45 degrees, but that's not ideal. Am I interpreting this dial correctly? It's after the mixer pump in the water circuit, so should read the adjusted temp as set on the dial, in this case 45 degrees? What do I need to do to stop needing to adjust the combi flow temperature and to get the UFH to do that?