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Potterton EP 6002 controller replacement with 3rd Gen Nest help...

Discussion in 'Plumbing and Central Heating' started by burntcampervan, 4 Feb 2017.

  1. burntcampervan

    burntcampervan

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    Hi,

    I am replacing the above controller with a Nest controller but am having a bit of a problem working out how the system has been wired up. It works fine so rather than mess with it I am wondering whether I can just wire the Nest in from the current wiring points on the base board of the EP6002 controller?

    I found a diagram online that appeared to show it would be possible for the EP2 but the EP6002 has 5 contacts rather than the 4 on the EP2.

    Similarly struggling to find a decent installation guide online for the EP6002 which might help me understand what's there, but if it were possible my preference would be to be able to wire from the base board to the nest board. It's all out of the way so it doesn't need to be pretty!

    Thanks,

    Paul IMG_3522.JPG IMG_3927 2.JPG
     
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  3. stem

    stem

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    First of all it's not too difficult. Some are much harder that yours. Unfortunately there are no fixed standard ways of wiring these systems and much comes down to the personal preferences of the installer. Looking at the wiring, it would appear that your system is fitted with a room thermostat. Because the Nest has this function built in, any existing thermostat must be removed, but it can't just be disconnected or the wiring would be open circuit and nothing would work. So can you advise which wires from the EP 6002 programmer go to the room thermostat.

    I suspect that it may be the bottom left cable with the red wire connected to terminal 4. Can you confirm this please and if correct, where does the yellow wire connect at the EP 6002 I can't make it out in your photo. Alternatively, it could be the cable connected to terminal 5.

    Also, if you could advise what type of plumbing system you have. Do you have motorised valves to control the hot water & heating?
     
    Last edited: 4 Feb 2017
  4. burntcampervan

    burntcampervan

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    Thanks Stem - much appreciated. Pretty sure it's an S plan - two motorised valves and pump in the airing cupboard as per photo.

    You are correct that there is a thermostat - I will try and isolate which wires those are this afternoon and get back to you. Thanks again for your help.
    Paul IMG_5708.JPG
     
  5. burntcampervan

    burntcampervan

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    Hi Stem,

    I have tested and the thermostat was the red wire on terminal 4 as you suspected with the yellow wire going to the C connector. I have left the wires off in this photo.

    Cheers,

    Paul IMG_7897.JPG
     
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  7. stem

    stem

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    Good. thanks for that, that was very helpful you do indeed have an 'S Plan' and I can see how the switching is wired. Two last questions and I should be able to give you a list of what goes where.

    1) There will be a live wire that goes to the central heating motorised valve's brown wire. It will be either the wire remaining in the 'C' terminal or one from the '5' terminal, can you confirm which terminal it is?

    2) The remaining terminal (either 'C' or '5') that doesn't go to the motorised valve should be linked to a permanent 'Live' somewhere, can you see if you can see where it goes?
     
    Last edited: 5 Feb 2017
  8. burntcampervan

    burntcampervan

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    Hi Stem,

    I am working on the assumption that the central heating valve is the one just above the pump on the bottom of the airing cupboard photo & that is indeed wired to the C terminal.

    The remaining terminal 5 is looped directly to the live by a brown wire which you can sort of see in the photo above.

    Hope that makes sense?

    Thanks,

    Paul
     
  9. stem

    stem

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    Great, that's very helpful. So:

    Remove the thermostat cable wiring from EP6002 terminals C, 4 and N, and the existing room thermostat from the other end of the cable.

    EP6002 Terminals A and B don't actually do anything functionally, they are just connectors, so the two wires in A will need removing and re-connecting together, and the two wires in B will also need removing and re-connecting together.

    EP6002 Terminal N is 'Neutral' so at the Nest this will also be the 'Neutral' terminal for all Neutrals in the EP6002 'N' terminals on the left.

    EP6002 Terminal L is 'Live' so at the Nest this will also be the 'Live' terminal for all permanent live connections. The Nest Heatlink L terminal, should also be linked to the two common terminals 2 and 5

    EP6002 Terminal 1 is not used by your system.

    EP6002 Terminal 2 is not used by your system.

    EP6002 Terminal 3 is 'Hot Water Call for Heat' so this will go to the Nest terminal 6

    The wire presently in EP6002 C terminal that goes to the live of the heating motorised valve is 'Heating Call for Heat' so this will go to the Nest terminal 3

    You may find that because of the number of wires that need to go in the Nest Heatlink L and N terminals, that if there is not enough space, you may have to run a single wire from the terminal to another connector and put two wires in that.

    If you wish to use the disconnected thermostat cable to provide the 12v power for your Nest Thermostat, you can do so by connecting a wire from T1 at the Heatlink to T1 at the Nest thermostat, and another wire from T2 at the Heatlink to T2 at the Nest thermostat.
     
    Last edited: 7 Feb 2017
  10. burntcampervan

    burntcampervan

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    That's exceptionally helpful and clear - thanks Stem - much appreciated. I think what I will do given the volume of wires is like you say run a single wire from nest box which isn't too roomy to a set of terminals to group everything together.

    Thanks again.

    Paul
     
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