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Installing Smart Thermostat

Discussion in 'Electrics UK' started by John Prosser, 24 Jan 2021.

  1. John Prosser

    John Prosser

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    Hi

    I’ve bought a Smart thermostat to replace my existing. I thought I had the wiring sorted but it’s not working. Any advice gratefully received. Pictures of new and old attached.
    Thanks!

    upload_2021-1-24_11-17-25.jpeg upload_2021-1-24_11-19-18.jpeg upload_2021-1-24_11-20-34.jpeg
     
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  3. CBW

    CBW

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    From your Drayton/Invensys to smart stat

    L to L
    N to N
    3 (call) to 2
    Link L on Smart stat to 1 on smart stat
     
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  4. ericmark

    ericmark

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    Have you fitted link, the old one should have a neutral, but it will work without one, so if not working with link then maybe there is no neutral just because there is a neutral wire grey it does not mean it is connected at the other end.
     
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  5. John Prosser

    John Prosser

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    Thanks for the replies. That is how I’ve wired it - with a bit more testing it IS working but has a 3 min delay on powering up. I guess that’s an energy efficiency thing. I have another to do now that I’m not sure about though so will be posting again if you’re able to help...
     
  6. John Prosser

    John Prosser

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    This one is for underfloor heating. I’m looking to replace a honeywell CM907.
    upload_2021-1-24_12-26-13.jpeg

    There is a grey wire not connected that I’m hoping will provide power?

    The new controller I have for this is slightly different (should I have bought the same as above?)

    upload_2021-1-24_12-26-52.jpeg

    Really grateful for your help
    Thanks again
     

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  7. CBW

    CBW

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    So the grey might be an unused neutral, you may need to trace this though. Again L and N (if indeed the grey is a N), then link L on smart stat to closed (1) on smart stat, black is call wire, so 2/open on smart stat.
     
  8. John Prosser

    John Prosser

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    Grey is not N unfortunately. Is this likely to be something I can wire in? Would it be at the pump or boiler or ? Thanks
     
  9. CBW

    CBW

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    Do you know what it is?
     
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  11. John Prosser

    John Prosser

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    No. I tested with a meter but no circuit. otherwise don’t know how to find out unless I can find other end at pump or boiler .
     
  12. CBW

    CBW

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    It may go to a wiring center. Otherwise, you’ll have to have another battery operated thermostat.
     
  13. ericmark

    ericmark

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    The delay is for heat pumps, the pressure needs to drop before a restart.

    Seems likely you need to look at other end of cable, for some daft reason some boilers put the electrical connections inside the sealed part of boiler so be careful.

    Only smart thermostat I know which is battery powered is Nest e
     
  14. John Prosser

    John Prosser

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    I’ve dismantled a cupboard to get to this...

    upload_2021-1-24_15-11-3.jpeg
    upload_2021-1-24_15-11-57.jpeg

    There is a grey that is not wired in (folded behind black in pics). It is in grey trunking as is the case at the sensor end. I am thinking to connect in with the other grey on the lhs which is connecting through to blue/neutral on rhs. Make sense?

    (I will turn power off!)
     
  15. CBW

    CBW

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    It seems like it could be.
     
  16. John Prosser

    John Prosser

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    Bingo! Thanks for your help - all working!! Now to rebuild the cupboards ☹️
     
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