Underfloor heating - supply & return flow temperature question

[dl1973]

Hi
I have a wet based underfloor heating system and I've noticed that the stone floor in our kitchen isn't warming up evenly. There is one patch that is much warmer than other areas. I have noticed that when I look at the manifold the supply temperature is running at around 50 to 55 degs but even after the heating being on for over an hour the return temp never gets over 40 degs. My basic understanding is that the flow and return should balance and eventually get to roughly the same temp? Could this signify a problem, i.e. an air lock in the pipes and if so what is required to fix this?

 

[Riley]

I’d think more likely the pipework hasn’t been evenly spread. Is the cold spot where two circuits meet

 

[dl1973]

I assume you mean hot spot not cold spot?
Unfortunately I didn’t lay the pipe myself but i can dig out the cad drawing of the suggested pipe layout
In terms of the temperatures on the flow and return parts of the manifold why would there be a 10+ degree difference?

 

[ShaunCorbs]

That's the heat being taken into the screed they will never be the same on a heating circuit your looking for around 15dc difference