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Nest Underfloor wiring issue

Discussion in 'Electrics UK' started by Rushi P, 28 Feb 2020.

  1. Rushi P

    Rushi P

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    Hi All,

    First time I've ever posted on a forum. I was wondering if anyone can help me please.

    I've had a new heating system installed for a couple of years now but have an issue with our underfloor heating, connected to a Nest thermostat, probably the wrong thermostat to use but this is the issue im having.

    When I request heat for the underfloor heating (wet system), the boiler heats up and sends hot water to the zones (4), but I do not think its going all the way through to the return pipe, as the 'return' pipe doesnt seem warm enough.

    BUT I noticed the boiler heats up to 73/79, then almost instantly the boiler goes off again, then it will start up again to send hot water, little while after stop (continuous pattern). So there is never enough hot water flow going through the pipes. This winter hasn't been pleasant, the floor doesnt heat up enough.

    During the first year it was working great, I'm not sure what has changed.... Im wondering if I should simply swap the Nest system to a 'manual' Polypipe thermostat.

    I thought it could be wiring, but then again I haven't tinkered with it. I'm just wondering what part of the system would stop the boiler from sending continuous hot water.

    Many thanks, Rushi
     
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  3. bernardgreen

    bernardgreen

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    To me that sounds like either the pump that circulates the water is not working or valves controlling which zones are to be heated are not opening,
     
  4. Rushi P

    Rushi P

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    Thanks Bernard, sorry I forgot to mention these important points. I'm getting a loft conversion done at the moment, the builder has some knowledge and advised that the pump and valves (are these the actuators) are functioning.

    For the pump - he unscrewed the bit in the middle to check
    Valves - unattached a couple and put pressure on the point to check
    Pipes - Also drained some water to see if there is spats of water to indicate air gaps
     
  5. oldbutnotdead

    oldbutnotdead

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    Does sound like some sort of flow restriction going on (causing the boiler to reach its set max temp before the room reaches comfortable temperature). I'm no expert on the things but I thought UFH systems were meant to run at quite low temperatures (45 ish) for long periods. Is it possible you've cooked a pipe so it has softened and collapsed?
     
  6. bernardgreen

    bernardgreen

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    Having "some knowledge" can be worse then having no knowledge. Find a heating engineer to diagnose the problem.
     
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  8. ericmark

    ericmark

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    I would agree, we all know the idea, which is two pumps, one circulates water around whole system, the other re-circulates water around the under floor heating so the under floor bit can be cooler than the radiators, clearly if under floor was as hot as radiators one would have a problem walking around, and you have a bank of controls that sets the maximum temperature of under floor bit in main no hotter than 27°C.

    But after that point it starts to get complicated, and not all systems are the same, so it needs some one who knows your system.
     
  9. Lower

    Lower

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    What temperature is the underfloor heating mixing valve set to?
     
  10. Rushi P

    Rushi P

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    Thank you everyone for the guide. I’ll have to get an engineer to have a look. Just some answers to some of the points.

    the pump temperature is to 40. I really hope the pipes have not collapsed.

    I’ve added a picture of it helps, thanks all
     

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  11. stem

    stem

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    The Nest thermostat is simply an 'on/off' switch the same as any other thermostat and from what you say it would appear to be switching 'on' OK. So if the 'heating on' light is showing as below...

    Capture (1).JPG

    ...and it has been correctly installed, then the thermostat is doing its job. From the previous posts the consensus is that the problem is not Nest related.
     
  12. Eccles

    Eccles

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    Oh dear how often does one hear about these wretched under floor systems playing up/going wrong and such a pain to get them sorted as old pals of ours discovered a couple of years ago (and the system was only 4 years old). I know this is not helpful but get rid and get a larger radiator in the room concerned would be my advice.
     
  13. DIYnot Local

    DIYnot Local

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