Installing Nest 3rd Gen Thermostat - Worcester Bosch Greenstar 29 CDi

[Ouchmythumb]

Hi All,

I'm looking to replace my existing wireless thermostat with a nest 3rd gen. I know how to disconnect the current thermostat ribbon cable and realize that I will need to do that for the NEST to work properly.

The connections for the heatlink are shown below.

I had a look at another post for a 32cdi posted back in Jan and I think that has helped me with the wiring of the heatlink.

My problem comes with the wiring on to the circuit board in the boiler and i really don't want to mess this part up.


Below is an excerpt from the WB 29cdi manual to show what I have.

Right now I have my incoming mains Live Neutral and Earth (see circled)

On the heat link I have taken a 5 core flex and did the following (taken from another post - All thanks to JohnMDC)
--------------------------------
On the heatlink connect:-
Blue to N
Brown to L and put in a link from L to 2 and from 2 to 5
Green/yellow to earth
Black to 3
Grey to 6

Read more: https://www.diynot.com/diy/threads/...-bosch-greenstar-32-cdi.475252/#ixzz4wgurEMOf

--------------------------------

So from this I think the heat link is wired up properly.

On the boiler I reckon I will need to insert the green/yellow to the earth block
the Brown to the L on the ST10 terminal and the Blue to the N on the ST10 terminal in order to supply power to the heat link (whilst keeping existing power feed to boiler.

so now I have two wires left (Black and Grey)
I have a small link type connector clip currently connected to ST10 which I will need to remove but now what? Im stuck.... any hlp would be appreicated. I have trawled the web and cant see anything from anyone doing an install with a nest to a 29cdi..

Thanks all - Mo

 

[Ouchmythumb]

Actulally I think i may have sussed it -anyone correct me if im wrong.
The LS terminal is live as soon as the boiler is powered on, so the supply to the heatlink will come from that, therefore im left with only one wire to connect which will be the black one for the CH, that will go to Lr terminal. There is no control for pre heat so the the grey cable will be redundant...
so on the heat link i just need to remove the link to number six and disconnect the grey wire from there as well..

 

[stem]

Sounds about right to me.

1. Ls is as you suspect a permanent live (Ls = Live Supply) This would go to the Heatlink L, and also be linked to the 'Heating Common' 2
2. Ns is 'Neutral Supply' so self explanatory
3. Lr is 'Live Return' this goes to Heatlink 3, "Heating Call for Heat"
4. Earth to earth as applicable

 

[Ouchmythumb]

Thanks Stem - perfect. Will give it a shot when I get home.