Underfloor heating problem

[Thecommonfox]

Hi All,

Sorry if this has been covered but I cant see it anywhere.

I have moved into a house with UFH, the heating works but the issues seems to be that there is not enough flow to heat up the rooms.

the flow pipes are hot but all returns (except a small bathroom loop) are cold. I have done a fair bit of trouble shooting and have ruled out the following
- Air in the system / sludge - not this I have drained the system then flushed it with the hose, filled it with cleaner (fernox) and drained and filled it a few days later.
Each loop will work if it is isolated it just seems like there is not enough power / pressure to go around. the pressure on the boiler is 1.3 cold and 1.7 warm so that is not the issue.

I have ran the system with the actuators off for maximum flow. The flow meters do seem to be an issue. They are on the return manifold as opposed to the flow. as a result there does not seem to be any flow going through them (even in the small loop that is working) and they dont seem to be set at all, they are also filthy. I have tried to adjust them relative to the lenght of the loop but as they are on the return and there is no flow going to them I cant.
I know the answer to this is to change the manifolds around but is this my main problem, even when I open up the flow meters it does not improve the flow.

could it be that my pump is not powerful enough. it is on the 3rd setting but I have no way of knowing if it is enough. aside from the boiler there is no pressure gauge on the monifold.

I have included a few pictures. any advise is arrpeciated as it is driving me mad

 

[rbranco]

No pics.
Describe system setup, boiler, which piping plan, controls etc.

 

[Thecommonfox]

Sorry, see Pictures attached
Not sure of the system set up but basically the 3 pipes below do the largest 3 loops then the vertical pipe to the left of the manifold takes hot water to a second manifold that heats the hall and bathroom

Top one is the hot flow

The vertical pipe leads to a second manifold - see below

 

[rbranco]

Are there any radiators or is it all UFH?
Do you have a HW cylinder as well, is it a regular or system boiler?
Is the whole house at a single temp? does not seem any of the UFH zones have independent control.

Someone will probably say its best to have individual mixers on the UFH manafold and a circulating pump for each one which would be variable speed.

 

[Thecommonfox]

Hi

Yes a regular unvented HW cylinder, just a normal boiler. The house has 5 Rads also on the same system. they all work perfect.

I can see the logic in seperate pump and mixing valve for the second manifold but it does only have 2 relatively short loops. even if I isolate the flow to the second manifold the flow still fails to completey get around the main manifold with its three loops. only if I isolate everyting except 1 loop with i get a good return flow

 

[rbranco]

Hi

Yes a regular unvented HW cylinder, just a normal boiler. The house has 5 Rads also on the same system. they all work perfect.

I can see the logic in seperate pump and mixing valve for the second manifold but it does only have 2 relatively short loops. even if I isolate the flow to the second manifold the flow still fails to completey get around the main manifold with its three loops. only if I isolate everyting except 1 loop with i get a good return flow

I would probably split the system
One loop between the two UFH manifolds with single variable pump and mixer, this then takes its feed from the main loop which heats up the radiators using the existing pump.
Ide speak to an installer, map out the whole system first, get every bit of detail before you make any decisions.

 

[Thecommonfox]

Thanks for the advice