Wiring thermostat to Vokera 25c boiler

[Emilia]

Hi all,
I was wondering if someone could help me figure out where the thermostat (fitting nest e 2nd generation) wires should go in my Vokera boiler? It’s a 2 core wire which I connected to nest heat link on the wall and i am assuming it has to run straight to the boiler. Now, where exactly do I connect the 2 wires? It’s not very obvious as the boiler doesn’t have the usual markings you’d expect to help find thermostat connection.
I should mention, at the moment I have a fixed timer on the boiler so I am assuming this will need to come off once thermostat is working? There are 4 cables black, red, blue and brown.
I am attaching some photos.
Perhaps someone here can help?
Many thanks in advance.
Emilia

 

[CBW]

You can disconnect the clock, or set it to constant (Nest will override this). You’re looking for removing a link or existing thermostat - the block is marked M2 (which looks like the on you’ve circled).

You may also need the safety of the boiler checking out as some form part of the combustion circuit.

 

[vulcancontinental]

Remove the red and black from CN5 and the switching connections from the Nest go there. I assume power to the Nest is taken from somewhere else, if not you could remove the brown and blue wires from the same flying lead as the red and black and power the Nest receiver from there. Obviously the clock will not work when this is done.

 

[ianmcd]

Remove the red and black from CN5 and the switching connections from the Nest go there. I assume power to the Nest is taken from somewhere else, if not you could remove the brown and blue wires from the same flying lead as the red and black and power the Nest receiver from there. Obviously the clock will not work when this is done.

nest E is battery powered mate simply an on off switch

 

[Emilia]

You can disconnect the clock, or set it to constant (Nest will override this). You’re looking for removing a link or existing thermostat - the block is marked M2 (which looks like the on you’ve circled).

You may also need the safety of the boiler checking out as some form part of the combustion circuit.

 

[Emilia]

CBW so which Circe is M2 on my picture?
And what shall I do with the red and black wire after disconnecting it? Just use the terminal blocks to close it off? Nest thermostat only have 2wires blue and brown so where exactly shall I connect them?
to the same spot /terminal where blue and brown wires form the current clock go? Sorry they’re probably silly questions but I don’t want to blow up my boiler by adding wrong wire into a wrong place.

 

[ianmcd]

the two wires go to Com and NO doesnt matter which way round

 

[CBW]

CBW so which Circe is M2 on my picture?
And what shall I do with the red and black wire after disconnecting it? Just use the terminal blocks to close it off? Nest thermostat only have 2wires blue and brown so where exactly shall I connect them?
to the same spot /terminal where blue and brown wires form the current clock go? Sorry they’re probably silly questions but I don’t want to blow up my boiler by adding wrong wire into a wrong place.

No they’re not silly questions, if it saves you or your boiler from harm. Ian and Vulcan have also given sound advice. What’s currently connected to the red and black wires?

 

[Emilia]

Thanks CBW. black and red go from the clock like on picture then joint in a black terminal ‘thingy’ also showing on picture and ends up in a boiler under CN5 (picture attached)
The other 2x wires (blue and brown) divert from the black terminal ‘thingy’ and end up in the boiler in the great plastic block (circled in picture). So, my 2 core cable (blue and brown) running form the nest thermostat, does it have to replace the blue and brown mentioned above? (I circled them on the picture where I think I should swap blue and brown)

what do I do with the CN5 black and red wires which as mentioned run from the current manual click. Shall I just terminated them?

Picture …25F.jpg -manual clock
Picture …194.jpg connection between manual clock and a boiler (blue, brown, red, black)
Picture …897.jpg - nest thermostat wire to be connected to boiler.
Picture …A1F.jpg - current blue and brown awires running from the manual clock (see picture..194.jpg. Is this where I take them out and replace with nest thermostat wires?
What shall I do with black and red at CN5 as they will be disconnected from the manual clock at the other end.

vulcancontonetal said to ‘disconnect red and black at CN5 and the switching connections go there’.
Am I wrong thinking that blue and brown wires from nest should replace blue and brown that are currently running from the clock?
My question is: which part is responsible for thermostat?
CN5 or the other grey block that’s got currently blue and brown connected as on pictures?



thank you so much for all help!
Emilia

 

[CBW]

Personally I would do as Vulcan has suggested (he works for Vokèra) , and yes terminate the black and red in choc block.

Yes you’re wrong in thinking Nest wires go to brown and blue as this is mains voltage and won’t fire the boiler up for heating.

CN5 is responsible for the thermostat.

 

[Emilia]

CBW. Excellent! thank you so much.
Your reply is very much appreciated
So the last question is: what do I do with a black ‘thingy’ currently connected to manual clock as per …194.jpg
Do I just disconnect the two and leave it as it is?

 

[CBW]

The black connector block underneath, you could disconnect it, but it’ll still be live from the pcb, so either leave as is (clock will still tick) or remove the brown and blue at pcb end (there are x2 brown and x2 blue, so only need to remove the clock feed).

 

[Emilia]

Ok thank you. What is PCB and where is it exactly? sorry! I really don’t know any of this so completely relay on your expertise .

 

[ianmcd]

It is very simple , the black and red wires in your pic go to Com and NO on the nest E the Tyco socket gets plugged in and the mechanical timer gets set to constantly on and the nest will control everything

 

[Emilia]

Ianmcd thank you but what is and where is ‘Com’ that you’ve mentioned?