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Nest Thermostat - Gloworm ultimate 30c

Discussion in 'Plumbing and Central Heating' started by Connor1995, 21 Jul 2019.

  1. Connor1995

    Connor1995

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    Hi all!

    I recently purchased a nest thermostat to accompany my gloworm ultimate 30c combi boiler. I originally wired the heat link to the drawing supplied with the instructions supplied with the nest but that didn’t seem to work and my boiler would only turn on once I went past the set limit on the nest thermostat.

    So I did a bit of research and found that apparently the drawings supplied is catered for American style boiler systems and found someone who had done a similar install. I have posted a link to the guide I followed below for your reference.

    Previous post for similar boiler:
    https://www.diynot.com/diy/threads/glowworm-flexicom-30cx-and-nest-v3-thermostat.494097/

    Tutorial:
    https://www.cnet.com/uk/how-to/how-to-set-up-a-nest-thermostat-in-the-uk/

    Essentially I have tapped in directly from the boiler 230v supply to the heat link then took a jumper cable from the Live terminal of the heat link and put that into terminal 2 on the heatlink. Then added one more core from terminal 3 on the heat link then wired it into the ‘RT’ terminal on the boiler as suggested in the tutorial/forum post.

    Now this has fixed the previous issue I had with the boiler not turning on until I went over the set temperature on the thermostat but now it seems like my central heating is not heating when I change the tempature on the thermostat and when I go to my boiler I have a flashing radiator symbol.

    If anyone has any ideas as to how I can fix this/where I have gone wrong it would be much appreciated.
     
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  3. muggles

    muggles

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    The flashing radiator symbol means that the boiler is receiving a demand for heating, so it sounds like you've got that bit correct at least
     
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  4. mrStat

    mrStat

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    Just an idea as I don’t quite understand what it is that’s not working, but you have set the radiator temperature on the boiler to 65/70ish? If set too low, the Nest will “call” for heat but the boiler will just sit there staring at you.
     
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  5. Do you have any other control system that need to be set to on? Such as mechanical time clock?
     
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  6. Connor1995

    Connor1995

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    Hi,

    Thanks for your reply! I did have it set to a lower tempature but that is because whenever I increase the temperature on the boiler it actually increases the room tempature rather than being controlled through the thermostat and calling for heat?

    Thanks.
     
  7. Connor1995

    Connor1995

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    No not that I am aware off.
     
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  8. mrStat

    mrStat

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    Sorry, can you post some pictures of your wiring please? I am a little confused as to what the fault is...

    Nest is supposed to turn on when turned up above the current temperature? And will turn off when the set temperature is lower than the current? Surely this is right?

    Sorry, I didn't understand the previous issue...

    So are you saying that the heating is on permanently now?

    If so... Have you taken out the 24v link?
     
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  10. Connor1995

    Connor1995

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  11. mrStat

    mrStat

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    You need to take the 24vRT link out

    24vLink.jpg
     
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  12. Connor1995

    Connor1995

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    Hi,

    That seems to have fixed the problem! Thank you so much! Can you explain to me why the link was causing this issue?

    Many thanks.
     
  13. mrStat

    mrStat

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    Great to hear.

    As for the reasoning... We use a variety of system wiring configurations in the UK, some low voltage and some high voltage. As such, some boiler manufacturers have both high and low voltage sides to their control boards. On packaging and shipping the manufacturer will leave a link in the low voltage side of the boiler and during commissioning the link should be removed by the installer. In reality, you could have put one of the 24VRT connections into 2 on the Nest and the other into 3... Once bridged out, it will enable the heating. If there is no bridge there, the heating will be disabled unless it see's 240v on the 240vRT terminal... So in short, you can use low voltage or high voltage controls with your boiler... And Nest can be volt free, low voltage or high voltage.

    Because the terminals on a Nest Heatlink are sooooo small, I often will use a 5 core cable, L+N and then use the 0v or 24v switching circuit on the boiler with a black and grey cable so I don't have to try and piggy back onto the Live connection.

    Hope this explains it? But in short, it is to give flexibility with different controls and different wiring styles.
     
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  14. Connor1995

    Connor1995

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    Yeah I understand. I have a familiarity with electrics just not in the case of domestic/wiring up boiler. Thank you again for your help you are a life saver
     
  15. ericmark

    ericmark

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    Please note, only in USA is the domestic mains supply called high voltage, in the UK like most other places in the world it's called low voltage, 230 volt AC is low voltage, and 24 volt is extra low voltage.

    Nest can work with any voltage up to 230 volt mains, it has volt free contacts so although with Nest gen 3 it needs 230 volt to work, it can switch 24 volt, it also has OpenTherm which if the boiler also has OpenTherm I am told works far better, I note you boiler has a bus connection but not sure if OpenTherm? and Nest E is a battery powered version, which works I am told well with combi boilers where Nest does not control hot water.

    Having just fitted Nest Gen 3 the wiring was repetitively straight forward, the heat link is small, so I fitted a wiring centre below it to reduce wires in such a small space, and a second wiring centre next to the boiler, but mine was doing DHW as well.

    However I found the software set up rather a problem, lack of good instructions I blame, listing boiler type to start with, seems mine is called "Other" then explaining what should happen, when the boiler turned on without being scheduled I used the on line help and phone call, all they wanted to do was send a pro installer to fix it, and if my fault I would need to pay, turns out nothing wrong, it was anti legionnaires software kicking in, there was nothing in paper instructions to even say it existed.

    As to how to work it from phone, not even using Nest software, but Energenie the software for the TRV works Nest I expected the reverse.
     
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