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Nest 3rd Generation Upgrade

Discussion in 'Plumbing and Central Heating' started by haz786, 8 Jan 2020.

  1. haz786

    haz786

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    Hi all,

    I've purchased a Nest 3rd Gen & looking at replacing the current controller. The system currently has a combi boiler & electric water heater.

    Image of current cabling is attached - cables in N, L, 3 & 4.

    If you could direct me where this corresponds on the HeatLink, that would be greatly appreciated.

    Also - how does the electric water heater factor into this? It is located on the 1st floor and powered manually with a switch when required (so don't think it's directly connected to the controller but would like it linking into Nest if possible).

    Thank you
     

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  2. muggles

    muggles

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    What make/ model is your existing controller?
     
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  4. haz786

    haz786

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    Hi there,

    Existing controller is a Danfoss FP7898
     
    Last edited: 9 Jan 2020
  5. stem

    stem

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    I seem to think that product refers to the 715 as below. is that correct? It will say on the drop down door bottom right corner.

    DF.JPG

    If so, there is something a bit unusual. Are you sure you actually have a combi boiler? A combi boiler heats the hot water instantly whenever a hot water tap is opened, and the hot water goes directly from the boiler to the tap without the need for a hot water cylinder (tank). However, if your programmer is the same as the one above with a 'tap' symbol and the wire connected to terminal 3

    20200108_211823.jpg

    That indicates that the boiler is connected to a hot water cylinder. I suspect that this is the case and that the cylinder has an immersion heater fitted as a back up. Is that right?

    If the boiler is connected to a hot water cylinder and the programmer is a 715, installation of a Nest thermostat has been covered on here before. You can find an example here. You don't have a wire in terminal 1, so your system is slightly different. Just ignore that bit.
     
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  7. ianmcd

    ianmcd

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    That is a programmer so unlikely that you have a combi boiler post pics of your boiler and what you are calling an electric water heater
     
  8. DIYnot Local

    DIYnot Local

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