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Help with Rehau wet underfloor heating system

Discussion in 'Plumbing and Central Heating' started by glastoveteran, 17 Oct 2020.

  1. glastoveteran

    glastoveteran

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    Hi all,

    We are the new owners of a 30 year old house with a Rehau UFH system over 16 zones and 2 manifolds fed by a Vaillant ecoMAX boiler. There are no radiators.

    The system isn't working well at all and I would be really grateful for any advice. Lots of zones just don't get warm, even though the thermostats and actuators for those zones are working correctly.

    I've spoken to a few different underfloor heating specialists in my area and none of them are willing to take on the maintenance of an existing system, so I've taken it upon myself to try to work out what is needed to get it up to scratch and then arrange a plumber/electrician/gas safe engineer to do the work.

    I believe the issues are:

    1) The whole system is powered solely by the pump from the boiler - no separate pumps.

    2) There are no blending valves on the manifolds.

    3) There are no flow gauges for the manifolds and as far as I am aware no way to adjust the flow rate for each circuit.

    My questions are:

    1) Can I just add pumps and blending valves to the existing manifolds? I assume one I'd need one on each manifold?

    2) As I'm not sure if it's possible to adjust the flow rate to each circuit with the existing manifolds, would that mean it would be necessary to replace the manifolds anyway?

    3) Given that I don't have much info about the design of the existing system and circuit lengths, is there a recommended technique for working out flow rates?

    4) Am I better off spending more time searching for someone willing to take this on?

    One of the existing manifolds:

    [​IMG]


    Thanks all.

    Alex
     
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  3. glastoveteran

    glastoveteran

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  4. Mr Chibs

    Mr Chibs

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    Doubt you’ll find out much info about a system of this age.

    I’m surprised all those loops can be powered by the boilers single pump.

    Recently I Installed a single room kit, but even this had a pump and blending valve and it was only for 28 sq m.

    Have you spoke to the manufacturer as a start?
     
  5. picasso

    picasso

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    Have the manifolds changed, you can pick up manifolds with pumps, flow meters and blending valves rather than messing about trying to adapt what you have, I doubt the system ever worked properly.
     
  6. glastoveteran

    glastoveteran

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    Thank you both. I agree I cannot understand how the previous owners have lived with this system for close to 30 years, as it can't have worked properly.

    I haven't been in contact with Rehau yet though I guess it's worth a go.

    One company I spoke to said I would struggle to replace the manifolds because the underfloor pipes are 17mm and they weren't aware of any manifolds that would fit them, but I will look around and see what I can find.
     
  7. Mr Chibs

    Mr Chibs

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    Maybe you need a pump or pumps, the manifold might not be the issue.

    What happens if you turn some of the circuits off... (If possible) do the other ones get warmer.

    Not that I’m an expert, but 17mm pipe is not the norm, you might be able to get a reducer to take you to 15mm, then you could change the manifold.

    food for thought!

    good luck, let’s us know how you get on.
     
  8. picasso

    picasso

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    Adaptors are available so changing the manifolds would not be a problem (but not cheap)

    Capture.PNG
     
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