Underfloor heating system not getting hot this winter.

[puffafish]

I've check and unjammed the pump, so that's pumping fine. I've flushed all the UFH pipes, so they're primed and not blocked. I've checked all the motorised valves, and they all appear to activate: you can hear/see them switch as expected. I've also looked at the mixing valve (where the hot feed and cold feed mix so the UFH doesn't get too hot): if you set it to fully cold the flow through the UFH pipes is good, but setting it to anything warmer than that means gives no flow at all. I've swapped out the mixing valve (as I have no way to prove it works) with a spare I've had in the loft for a while (which I'm assuming works). But I'm still getting the same response.

Yes I have bled the system and there is heat in the radiators so I know there is heat available to get into the UFH system. I have also checked the flow pipe to the manifold, and that is supplying water.

When I have it all connected up and turned on, I'm getting water out of both bleeding valves.

It could be as simple as my spare mixing valve is also broken, but I don't want to spend £130 unless I have to.

 

[Johntheo5]

Pour a trickle of water through the hot inlet of the removed TMV, does it come out the mixed outlet? Ditto with the cold side, nothing should come out the mixed outlet.

 

[puffafish]

If I pour water into the hot inlet it flows out of the mixed outlet. Regardless of the temperature/mixture setting.

If I pour water into the cold inlet it doesn't flow out of the mixed outlet. Regardless of the temperature/mixture setting.

 

[Johntheo5]

Thats a bit strange since I presume this TMV was acting in the same manner as the spare Ie a good circ flow when turned to cold, which would indicate that the cold (recirc) port is open to the mixed outlet, what is the temperature range of this TMV?, You say you unblocked the pump so its now running OK. The cold & hot pipes are connected properly?.
Can you post a photo of the manifold showing the TMV and pump etc.

 

[puffafish]

 

[Johntheo5]

The range is 25C to 60C so even at minimum setting should initially be looking for hot only which it seems to be?.
have a look through this in case you had it apart and maybe didn't reposition some part correctly that they mention here.

Mixing Valve Issue

Hi All, I have an issue with a JG Speedfit mixing valve on my UFH (attached image). The original problem was that the pipe from the boiler to the valve was hot, but there was no hot water getting any further into the system, despite all valves being open and the pump running. Assumig a problem wi...

forum.buildhub.org.uk

I took one (different make) like this apart for someone who was experiencing somewhat similar problems and was quite surprised at the amount of (finger) force required to push the piston shuttle open to admit hot water, its spring loaded to push the piston to open the HW port and the mixed flow sensing phial then forces it partially/fully closed to throttle off the HW and admit cold water, I just put a bit of silicone grease on the sealing O ring in the body and it was fine after that.

 

[Johntheo5]

Could there be something stopping the returning cold water getting back to the boiler?, air locked maybe.

 

[puffafish]

Could there be something stopping the returning cold water getting back to the boiler?, air locked maybe.

Can't see how. 22mm pipe all the way. Nothing else on the way.

 

[puffafish]

The range is 25C to 60C so even at minimum setting should initially be looking for hot only which it seems to be?.
have a look through this in case you had it apart and maybe didn't reposition some part correctly that they mention here.

Mixing Valve Issue

Hi All, I have an issue with a JG Speedfit mixing valve on my UFH (attached image). The original problem was that the pipe from the boiler to the valve was hot, but there was no hot water getting any further into the system, despite all valves being open and the pump running. Assumig a problem wi...

forum.buildhub.org.uk

I took one (different make) like this apart for someone who was experiencing somewhat similar problems and was quite surprised at the amount of (finger) force required to push the piston shuttle open to admit hot water, its spring loaded to push the piston to open the HW port and the mixed flow sensing phial then forces it partially/fully closed to throttle off the HW and admit cold water, I just put a bit of silicone grease on the sealing O ring in the body and it was fine after that.

Not sure how this could be the case for both of the valves I've tried. I also can't find any springed part in mine.

 

[Johntheo5]

Strange that theres no spring. For interest, here's a TMV I took apart years ago to figure out how it worked.

 

[Madrab]

I presume this will be close to your setup - as you can see the thermomix blending valve components and if you are missing a spring then I don't think that's correct but you would need to get a part number

https://www.underfloorheatingsystems.co.uk/wp-content/uploads/2019/11/Thermomix-IM-ZINS970370_002.pdf

Without knowing the exact model of your blending valve - can you find a part number? - then a similar service kit would be this

Again it's certainly has a spring and all other reliance service kits are very similar and all have a spring return.

 

[Johntheo5]

Here's one from Altenic? I think, although it seems to be blinding both the HW and the cold.

 

[puffafish]

After much additional research and thought, I have swapped the feed and return connections to the mixer.

Everything now works how you'd expect: feed gets hot, return slowly gets warmer but stays cooler than feed and you can set the temperature dial to whatever value you want and it works. So it looks like my feed and return pipes were labeled the wrong way around. And that is the cause of all my issues including why I couldn't set it to hotter than 40C!