UFH help

[Scott_D]

I have piped up lots of UFH manifolds before while subbing but I am always off to the next job while the boss commissions.
Today I tried to get this up and running but I am a bit confused by how it worked.

The UFH manifold and pipework was fitted by someone else, I repiped the boiler with 2x zone valves, auto bypass and additional expansion vessel. There were no instructions available and I couldn’t find much online for this manufacturer.

While running the heating and UFH pump the flow to the manifold is scalding and the return stone cold unless the blending valve temp was turned up to high then the return also got hot (gate valve lock shield is open)
I was trying to run it very low to start drying the screed.
I couldn’t adjust the flow on the heads at all, they just stayed the same.

 

[ShaunCorbs]

https://www.theunderfloorheatingstore.com/media/ufhs/manuals/ThermoGuard_UFH_Control_Pack_-UPM3.pdf

Have you opened / unscrewed the white caps

 

[ShaunCorbs]

Has the ufh been filled and flushed ?

 

[Scott_D]

thanks I will have a read.
White caps are loose.
The UFH was filled and tested by someone else, I didn’t flush it. It’s the return to the boiler being cold that has confused me, but gets hit when the blending temp is increased

 

[ShaunCorbs]

Do you have flow / boiler is happy when the valve is mixed ?

 

[Scott_D]

Do you have flow / boiler is happy when the valve is mixed ?

Yes. I didn’t leave it at 50 on the mixing valve for long as I didn’t want too much heating going if I go the screed.

 

[ShaunCorbs]

Would stick it on 25 flow and see how it goes

 

[Scott_D]

I assume if it’s working correctly the flow will just bypass the UFH and return to the boiler hot.
The mixing valve will then take heat as it’s required?

 

[ShaunCorbs]

Depending on a few things yes but the flow gauges should be working / showing flow

 

[Scott_D]

This full return flow/ no return flow may be my issue.
Doesn’t say how to change between the 2 though

 

[oz-plumber]

Could just be air in the UFH circuits.
Connect a hose to the manifold and flush through until no air is in the pipework.

The system may have been pressure tested without flushing