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Nest on an Vaillant ecoFIT

Discussion in 'Plumbing and Central Heating' started by hellohi, 29 Apr 2017.

  1. hellohi

    hellohi

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    I've made a mistake and my plumber has gone off on holiday (a month!!!) after installing a new Vaillant ecoFIT pure.

    My mistake? I didn't get him the Nest in time before he disappeared off so it's down to me to wire it in. I've got a basic understanding of electrics and wiring, but not sure about something on the ecoFIT pure.

    The terminals I think I need are "Burner off", "RT 24V" and "eBUS". From my searches on this forum, I understand eBus is Vaillant's own proprietary smart thermostat system and the Nest won't play nice with it.

    The wiring diagrams don't seem to refer to any of the above and from my understanding of electrics, the Nest wiring diagrams suggest that the Nest is controlling the overall on and off state of the boiler, rather that controlling the heating on and off of the boiler.

    Is this correct?
     
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  3. hertsboilers

    hertsboilers

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    Which ecoFTI? combi, system or heat only?
     
  4. AGAS

    AGAS

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    have you the right nest ?
     
  5. hellohi

    hellohi

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    ecoFIT combi - apologies for not mentioning this from the off

    I didn't realise there are different Nests? Mine is a 3rd gen.
     
  6. hellohi

    hellohi

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    For completeness, here's the wiring diagram from the ecoFIT manual;

    [​IMG]
     
  7. hertsboilers

    hertsboilers

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    In your case, Nest controls the heating only.

    Nest 2 comes from boiler live, and Nest 3 backs to boiler RT, also remove the 24v link.
     
    Last edited: 30 Apr 2017
  8. hellohi

    hellohi

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    Thank you.

    I searched and searched but all reference to previous Vaillant Combis was to ecoTECs where ports on the boilers are numbered rather than named. Serves me right for giving this ecoFIT a punt!
     
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  10. hertsboilers

    hertsboilers

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    After 2012 Vaillant started using RT not 3 and 4.
     
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  11. Steelmasons

    Steelmasons

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    RT plug is a two terminal jobbie with only one terminal used as the other terminal is redundant.
    Some have mistaken RT plug to be used as a 3 & 4..;)
     
  12. C_Addams

    C_Addams

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    I think I may have confused this... can you help me to understand? my situation is slightly different as I'm not using nest but a control system i've designed myself. fundamentally I have a 230v relay to turn things on and off with L and N. I have wired up RT with L to the left, N to the right. And I have removed the 24v RT loop. But flicking the switch has no effect. I know its not the switch as the switch is also controlling the pump on my heating manifold.

    any suggestions?

    mine is an ecotec pro 835
     
  13. AGAS

    AGAS

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  14. muggles

    muggles

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    I'm surprised flicking the switch hasn't made something go bang. The RT terminals are for Live only, not Neutral. In any case, you shouldn't be taking the case off that boiler to access the wiring unless you are Gas Safe Registered, as it forms the safety room seal on the boiler. My suggestion, therefore, is that you stop fiddling around inside the sealed casing and call a GSR to check the integrity of your boiler.
     
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  15. C_Addams

    C_Addams

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    Yeah Yeah, we're not all idiots...

    Anyway, I fixed it about 10 minutes after writing this post. I had the live and neutral terminals the wrong way around going into RT (it's really not well labelled) and now I can control things as expected, and thus the project continues.

    Help rather than condescension might be nice in future, ta...
     
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