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UFH added to exisiting Y Plan system - advice needed

Discussion in 'Plumbing and Central Heating' started by AMR1, 23 Dec 2020.

  1. AMR1

    AMR1

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    Hi folks,

    We recently had a 30m2 extension added to our house, we had a local plumber install UFH into this, along with new boiler and radiators - all the work was done by this plumber.

    We've had issues with the UFH not getting up to temperature (flow temp is only around 25c and room takes 5+ hours to go from 18c to 19c). I've tried several times to get our plumber to come back and fix this but he's getting increasingly shifty which has me worried.

    I'm looking for some advice on if what he's done is correct, and if not, what needs to be done to fix it, I am also getting a different plumber to inspect the work and give their view. Onto the questions:

    1. The system is currently Y Plan with a 3 port valve - my understanding is this should have been converted to S Plan as part of the UFH to allow it to be controlled independently?

    2. The flow/return for the UFH have been connected via a T from the flow/return to the boiler, but this has been done before the main system pump - my understanding is the T should be done after the main pump?

    3. If 1 and 2 have been done incorrectly, is this likely to be the cause of the UFH not heating up correctly?
     
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  3. muggles

    muggles

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    Yep, you're correct on all counts
     
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  4. AMR1

    AMR1

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    Thanks - unfourtnately this has all come to light after 2nd fix of everything, plasterboarding, new ceilings, new kitchen etc - even more disruption to look forward to fixing this then.
     
  5. picasso

    picasso

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    What boiler do you have ?
     
  6. AMR1

    AMR1

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    Worcester Bosch Greenstar 15Ri - regular boiler
     
  7. Madrab

    Madrab

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    The system can stay as a Y plan but the UFH circuit should have a 2 port on it to allow that to be controlled by it's own thermostat, sometimes it's just easier just to upgrade the whole thing to an S plus.

    Depends whether the UFH is fed by a manifold using it's own pump and blending valve. If it is then the pump needs to balanced with the system pump to ensure neither overdraws the other.

    Floor material dependent then the flow temp should be up at around 50Deg.
     
  8. Mr Chibs

    Mr Chibs

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    Recently had mine commissioned, very similar floor size.

    Mine had two 2 port valves and a thermostat for each, they work independently.
    Got a feeling mine is S Plan. My UFH is a polypipe ZRU.

    Combi running UFH and 11 rads.

    Running my boiler water temp at 45°.

    What surprised me, was how quickly the room becomes warm, I have it set to fallback to 15° overnight (don't think it comes on) and back up to 18° for the day.

    My screed was a liquid type.
     
  9. picasso

    picasso

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    If you want to keep the y plan you will need a blocking 2 port before the 3 port, and it would be easy enough to fit a pump between the boiler and the pump you have serving the 3 port, I am assuming you have actuators and a ufh controller ?
     
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  11. AMR1

    AMR1

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    the UFH does have a 2 port valve on it, manifold also has a pump and thermostatic mixer. Flow temps never get above 25-30c, regardless of the mixer settings.

    Our radiators also get hot when the UFH comes on, hence my thinking this should have been converted to S Plan when being fitted
     
  12. AMR1

    AMR1

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    No actuators as it’s two loops in a single room. Basically for the UFH we have a 2 port, then mixer, pump, and manifold. This is all connected to a Nest thermostat which controls the UFH
     
  13. ianmcd

    ianmcd

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    Might have been an idea to mention this in your origional post
     
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  14. Madrab

    Madrab

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    This would be dictated by a) the boiler flow temp and b) the blending valve. If you can't get the manifold inlet temp above 30Deg then you need to check the temp just before the tee to the UFH circuit (boiler flow temp), in the first place. If this is a typical > 60Deg then the blending valve isn't working properly and needs looked at.

    Yes, It would be much easier if the system had been changed to an S plus plan if you wanted the UFH as separate zone.

    Unfortunately it sounds like your 'plumber' isn't very experienced with advanced heating systems. Should be easy enough to retrofit to an S Plus plan though, as all you need to do is remove the 3 port (MID), branch the feeds and add in the 2x2 ports - 1 on each leg to Rads/HW. The other part is just the wiring and connecting the 2x2 ports into the wiring centre correctly, which should be close to the 3 port anyway. I presume the rad/hw system has a programmer and their own stats?
     
  15. AMR1

    AMR1

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    Apologies, I'm not an expert on any of this - my plumber has left me high and dry on this so trying my best to figure out what could be going on.

    For clarification - the UFH feed comes before the main system pump, UFH has a 2 way valve; followed by a thermostatic mixer, pump, manifold running two loops both in the same room. There are no actuators attached to the system. The UFH is controlled by a Nest thermostat.

    My problem is the UFH flow temps are low (20-30c) regardless of the mixer setting and that the radiators also come on with the UFH which I was told shouldn't happen by our plumber.

    Going back to my original question - is having the feed for the UFH coming off BEFORE the system pump acceptable or should this T be AFTER the system pump?
     
  16. AMR1

    AMR1

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    This is my concern that he doesn't know what he's doing and we've been left with 1/2 a job but paid for a full job. The radiators and DWH are controlled by a separate Nest thermostat and Heat link. Moving to S-Plan would solve one problem at least!

    The flow pipe coming into the UFH is hot, I can't give an exact temp but I'd say easily 60c+ just based on touching it. Boiler flow temp is set to around 70-75c (it's a dial with no gradiations so hard to tell exactly).

    The more I think about it the more this looks like a non-optimal setup (Y-Plan and plumbed in before pump) combined with a possibly faulty mixing valve?
     
  17. Madrab

    Madrab

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    It would always do that on a Y Plan, well that or it could even constantly heat the HW depending on what signal (or not) the valve is getting from the programmer, as the 3 port valve would always be open to at least 1 circuit.

    Need to think about it a bit more but that could possibly mean that the HW satisfied signal could be overridden if the UFH is calling and the boiler keeps running and if the last position was the HW or there's no power to the valve, then it could be overheating the HW.
     
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