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Please advise- Drayton SCR/ Digistat RF to Nest installation

Discussion in 'Plumbing and Central Heating' started by wylstar, 22 Dec 2016.

  1. wylstar

    wylstar

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    Hi,
    I am installing a Nest onto a Worcester 25Si combi. It is to replace a Drayton SCR/ Digistat +3RF. I wanted to double check the wiring- ie. can I swap it like-for-like?

    Wiring, as shown in the pics (http://imgur.com/a/Ri7GW), is currently:
    Blue- N
    Brown- L
    Black- 1 (C)
    Grey- 3 (Call)
    Earth (which will be put into a junction box in the Nest).

    Thanks for your help.

    IMG_0220 2.JPG IMG_7140.JPG
     
    Last edited: 22 Dec 2016
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  3. stem

    stem

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    It's not a straight swap. You need to make a minor change. The Nest (single channel version for Combi's) uses terminals 2 (Common) and 3 (Call for Heat) for switching purposes. The existing thermostat uses terminals 1 and 3.

    So, you will need to move the wire presently in terminal 1 to terminal 2 of the Nest

    I believe that your existing Drayton is only a thermostat. What is presently controlling the times that the heating is on? The Nest will carry out both functions.
     
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  4. wylstar

    wylstar

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  5. stem

    stem

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    So what is presently controlling the times that the heating is on for?

    The Nest is designed to replace the thermostat and the timer, not just the thermostat. the Nest will take over both functions.
     
  6. wylstar

    wylstar

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    The Drayton wireless RF unit (equivalent to the nest thermostat) controls the times. This is also the thermostat, and feeds wirelessly to the Drayton SCR (which is equivalent to the heat link).
     
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  8. stem

    stem

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    Your original post said you had a
    This is just a thermostat. It doesn't have time control, so something else would have to be installed to provide time control. This would have meant additional wiring mods to decommission the timing device.

    However, if you are now saying you have a Digistat +3RF as per your later hyperlink, then this is a Programmable Thermostat and does have time control, so you are OK to swap it for the Nest.
     
  9. wylstar

    wylstar

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    Apologies. It is the digistat +3RF I have. I've edited the first comment to reflect this.

    Thanks for all your help (and patience!).

    I will swap out as advised above.
     
  10. Nopotatos

    Nopotatos

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    Hi,
    I have a similar digistat scr.
    And am moving to nest thermostat e.
    Is there any chance you could attach an image of how it looks after you set it up?
    It would be very useful for me (and maybe others).
    My understanding is
    1 black - this would go to c
    3 grey - this would go to no

    then put the three remaining wires live, neutral and earth into the terminal blocks provided.

    am I missing anything ?
    Thx
    Conor
     
  11. CBW

    CBW

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    Sounds feasible, but hijacking an old post is against forum rules.
     
  12. Nopotatos

    Nopotatos

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    Sorry about that, i didnt realise, I posted a new thread with the same question.
    Thx
    Conor
     
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