underfloor heating problems

14 Jan 2010
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United Kingdom

having some problems with a ufh manifold.

have fitted this 'reliance manifold' for a friend of mine and cant seem to get it to work. its a new manifold - connecting onto an existing ufh setup (external pump and mixing valve)

i'm getting heat to the flow side of the manifold, but nothing coming through the return. have cleared all the air from the pipework in the floor and pressurised the boiler.

i dont have much to do with ufh, but from what i understand - the flow from the boiler should mix with the return from the ufh manifold and the premix should then enter the flow side of the manifold???

if you can see the crap drawing 'above right' that i've done - then i dont think this is happening. boiler flow goes from the pump straight into the manifold, port A on the mixing valve is the return from the manifold, port b is drawn from the flow and AB (the mix???) returns to the boiler.

the existing manifold did work, and not sure why this one doesnt

any suggestions??????

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providing actuators are operating correctly voltage and compatability could be pump sometimes you drain a system and sludge can dry and cause impellar to slow badly
Its looks completely wrong.
With a thermostatic mixing valve the primary pump will supply the load port which is port A.
Port B (the by-pass) will be supplied by UFH return.
Looks as if pump is pumping directly from boiler to manifold and not drawing water through TMV. TMV should be between boiler and pump.
also nothing to do with UFH good practice to turn pump head around so electrics are on top
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Mixing valve in a diverting application thus the mixing takes place at the T just before the pump. :idea:

As solman says could just be a seized circulator. With the circulator inactive over summer and no controller providing "exercising" !
pump doesnt seam seized, so i dont think thats the problem. the mixing valve is made by a company called 'oventrop' danish i think? it incorporates a pipe stat into it as well. - i think this maybe the problem - maybe the return from the ufh wont mix with the boiler flow, thus stopping the circulation. because the way this mixing valve works it doesnt make for an easy job just trying to swap it over - need to change a fair amount of pipe work.

john 67 - when you say turn pump head around - do you mean reverse the manifold, so that the actuators are on top????
looking at your diagram you have the blending valve installed wrongly.

On all the setup i install you have the blending valve between pump and boiler.

AB goes to pump
A is return from manifold but is also teed to return to boiler
B is flow from boiler.

If your boiler has it's own pump as i would guess then you also need to auto bypass across flow and return before blending valve.

Remember to also limit/restrict return flow back to boiler.
Or this..... which is what the OP has drawn basically.

I would leave the pipe work well alone.
Have you checked the circulator to ensure that it is revolving by turning the spindle with a screwdriver?
yes have tried the circulator - when running, took the bleed screw off - spinning ok. - on the previous ufh that we took out - the actuators where on the top of the manifold, where as on this manifold they are located at the bottom - by spinning the manifold around, do you think this will have any effect on the circulation?????

otherwise, i think i'm gonna try changing some pipework???????
i think so - they fill with water, between the 2 - 3 ltr mark. the springs inside dont seam to move. would this suggest its the wrong way around. on the manifold itself it shows what should be flow and what should be return, which is how i've connected it - because the mixing valve is in the 'diverting position' does this suggest that the flow and return on the manifold needs swapping around???
What flow and return temps are you getting on the loops?
havent put a temp test on the loops - but i'd say the flow is easily 60'c. the return is cold. every loop. this is why i suspect a faulty mixing valve??? blocked maybe?
Could be a faulty valve.
But from what you're saying about temperatures just about zero flow is taking place in the loops.

Page four shows the layout for the Tri-D TR which is probably your valve.
I think the connections are OK..


Does the set up have a separate primary circulator?
Try removing the thermostatic actuater and see if the valve pin is moving freely.
Also try removing the circulator and energise it to see if the impellar is turning.

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