UFH running too hot

[Bperry86]

Ok so have turned heating flow temp down fully. I’m now getting 26c flow to manifold and 24c to return. Blending valve still set at min.

I then upped the heating flow on boiler by just under quarter of a turn. This then got the flow temp to manifold to just over 40 and return at 30. Blending valve still set to min

 

[Bperry86]

Edit return temp on manifold is now 25c

 

[Bperry86]

Am I right in saying that the temp to the floor is the flow temp plus return temps divided by 2?

 

[Johntheo5]

Not directly related but probably some relationship.

 

[Bperry86]

Is that enough to verify the blending valve isn’t working?

 

[Johntheo5]

Yes, one might expect ~ + or - say 3/4C around the setpoint.

 

[portion]

I am commissioning my Wunda UFH. All the flow rates have been set up as per the design.
No matter what I set the blender to the flow temperature rises to 50c and drops to 30c as the boiler cycles. In addition if I set the blender to minimum the flow rates on each circuit drop to below 1 L/m from 2.1 and 2.5.
With a remote thermometer the flow temp of the pipe from the boiler as it enters the manifold is about 48c. The 2 flows on each circuit are the same. It's as if the blender isn’t doing anything. The floor is getting above the recomended 27c.
Wunda Tech Support are going to send me a new blender but they say the recommendation for the pipes from the boiler are 15mm and I have 22mm. I'm only using 2 ports on a 4 port manifold with a combined UFH loop of 220 metres. They say this maybe overwhelming the manifold and I should replace the 22mm pipes with 15mm

Anybody else had this problem?

I had similar problems to this. Couldn't get the mixer to lower the temperature enough.. and I couldnt just lost it from boiler as I've also got upstairs radiators to heat.
After lots of searching it seems the wunda blenders aren't well calibrated. I had to unscrew the tiny screw so set it to a lower minimum. That way you can also move the temperature gauge to the front (which for some reason is otherwise facing backwards). After some adjustments with the minimum it started working by limiting the temperature going into the pipes.