UFH Conundrum - No flow through manifold. Please Help!

[ShaunCorbs]

What boiler?

Worcester 27 system compact

 

[Chalked]

Hi
System should have a zone valve fitted the the heating side and the underfloor. Otherwise, ether the radiators or the underfloor will bring everything on.
But none of that will be causing your problem. It’s probably never been filled correctly. Follow the instructions on this video and it should work ( apart from the one that’s teed off!)
It’s basically the same as yours, except upside down

 

[Darren Jackson]

It looks like the 22mm pipe coming out of the top of your blending valve is connected to the flow and not to the return pipe, And the 22mm pipe going into the right hand connection of the blending valve is connected to the return pipe of the boiler instead of the flow pipe. If this is so it would explain why it only works when it is closed off as it is doing the opposite of what it should be doing. It is hard to tell from the pics but it needs checking that the flow and return are piped up correctly, and a auto or manual bypass and motorised valve should be installed as it does not appear to have them looking at the pictures. Hope this helps.

 

[Chalked]

It looks like the 22mm pipe coming out of the top of your blending valve is connected to the flow and not to the return pipe, And the 22mm pipe going into the right hand connection of the blending valve is connected to the return pipe of the boiler instead of the flow pipe. If this is so it would explain why it only works when it is closed off as it is doing the opposite of what it should be doing. It is hard to tell from the pics but it needs checking that the flow and return are piped up correctly, and a auto or manual bypass and motorised valve should be installed as it does not appear to have them looking at the pictures. Hope this helps.

Good spot mate.
It does look like it’s piped up backwards.

 

[Murdoch]

Bear with me , as I'm a spark ..........

How many room stats do you have controlling the UFH/ zones?

What happens if you turn the room stats up and down when the boiler is on? Give the actuators a minute or 2 to respond!