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Help Installing Nest Gen 3 with Vailant eco tech plus 637

Discussion in 'Plumbing and Central Heating' started by kirpan, 24 Sep 2016.

  1. kirpan

    kirpan

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    Hi Guys,

    I am a little cheesed off as I have already done in 1 boiler PCB board which I will have to order in.

    My Set up for the ground floor is:

    1x Vailant 637 boiler which does my ground floor heating and hot water
    1x Honey well programmer
    1x Honey well Room stat.
    and my system is Zoned.

    Tried changing the programmer with the nest installed leaving the Honeywell Room Stat on the wall, just did this to test so the trigger would start my boiler going, well that was the plan. Did not plug the nest room stat in as I wanted to see if the boiler fired up.


    So going by my photos on the Honeywell programmer I have from left to right
    Earth, Neutral, Live, then 3 (Hot water ON) Black, then 4 (Central heating ON) Grey.

    So I link the nest gen 3 as follows left t right

    Neutral, Live, Loop from live to 2, Grey cable (Central Heating On) 3, loop from 2 to 4, Black (Hot Water On) 5.

    I did this and my boiler would not even boot up. Well it would show for a moment a tempreature reading and showed some geberish on the lcd screen but the boiler was making no attempt to start up abd the screen would go blank, so I treid the original Honeywell programmer and still no go. Had to swap the PCB on the ground floor Boiler with my second boiler (Same Boiler make and model) and left the system with the original Honeywell programmer and it fired up.

    My second floor Set up.

    1x Vailant 637 boiler (PBC Not work at the moment as I had to swap it with my ground floor boiler)
    1x Honeywell Programmer
    2x Room Stat. One located first floor and 1 located second floor.
    and my system is zoned. So if my stat is turned down on the second floor but high on the first floor I will only get heating on the first floor.

    I was under the impression that the black wire is just a 240v trigger for hot water and the grey is a 240v trigger for Central heating.

    What am I doing wrong?

    Have I just been unlucky and the PCB should have been just fine and fired up or am I a idiot doing something terribly wrong and the boiler pcb would have went?


    Please, please, please HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!
     

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  3. muggles

    muggles

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    You shouldn't really be taking the front case off your boiler as it forms the room seal and should only be removed and refitted by a Gas Safe Registered engineer...

    It's not unheard of for Vaillant PCBs to fail just because the power has been turned off and on again. There are fuses on there though so it would be worth checking one hasn't blown before fitting a whole new PCB. I can't find anything wrong with your description of the way you've wired it up
     
  4. kirpan

    kirpan

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    Tried to change the fuse but no good. May try again tonight and pray it wont fail the second board.
     
  5. hertsboilers

    hertsboilers

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    Should be:

    Neutral, Live, Loop from live to 2, Grey cable (Central Heating On) 3, loop from 2 to 5, Black (Hot Water On) 6.

    What is your boiler version? with two big dial knobs, or all push bottoms. I am thinking what is wrong with your first PCB.
     
  6. kirpan

    kirpan

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    I have 2 big dials for heating and hot water.
     
  7. AGAS

    AGAS

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    whats the size of your house :eek:
     
  8. kirpan

    kirpan

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    Its big enough... Lol
     
  9. muggles

    muggles

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    I think the word you're looking for is "castle" :p
     
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  11. kirpan

    kirpan

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    Its not that big.. So do you think the pcb can be sorted or does it have to be replaced?

    Also cant understand why my first floor programer has a hot water wire to it. The second boiler doesnt do hot water, if I pressed the hot water button the light would come on but nothing would happen..
     
  12. kirpan

    kirpan

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    If anyone can help with the pcb I would be greatful, i know it has 2 spare fuses which come with the boiler but theres only 1 fuse on thr pcb right, or is there a hidden one somewhere.
     
    Last edited: 25 Sep 2016
  13. muggles

    muggles

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    You've got 74kW of heat...my reasonably-sized four-bed house uses 12kW. Sounds like a castle to me :p
    PCBs can't be "sorted" - once they've blown, it's time to buy a new one. There are companies out there who claim to be able to refurbish them, but there's no way of knowing whether their refurbishments are safe or not so I wouldn't recommend going down that route
     
  14. hertsboilers

    hertsboilers

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    It is an earlier version of ecoTEC, PCB is prone to be dead, I always carry one in my van.

    As @muggles said, CET at Watford is selling re-con PCBs.
     
  15. hertsboilers

    hertsboilers

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    74kW boilers for over 500 SQM!
     
  16. Agile

    Agile

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    The usual maximum heating requirement for a badly insulated house is about 100 W per square metre!

    But that boiler power is only 148 W per m2 so not that much over powered.

    Even so one boiler would do all the heating.
     
  17. kirpan

    kirpan

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    Finally got it working last night. I was unlucky the first time as I did do everything perfectly however the pcb just failed. This one nearly beat me as I was very close to not trying it as I had bad fortune the first time.

    You right Agile, the whole idea to have 2 boilers was if 1 went down the other could take over the whole house. I have 2 valves which I can turn to marry the 2 boilers together.

    Got another question. I have wired up both Ground and First floor. The Second floor has a room stat in the hall way and doesn't have a programmer. It would work when the first floor programmer was switched on for heating. Can I split the heating call to the boiler or should I not do this. So basically loop "3" on the nest link first floor to the nest link second floor. I have 3x nest, how do I wire up the last nest?
     
    Last edited: 27 Sep 2016
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