Installing Nest 3rd Gen Thermostat -Worcester Bosch Greenstar 32 CDi

[stem]

Hi David and welcome to the forum.

The thermostat receiver you have [MT10RF-Mechanical RF thermostat] is the same as the OP, and will unplug as described above.

If your boilers wiring terminals are also the same, then yes, the wiring will be the same. Unfortunately "Worcester 40cdi early model" doesn't help much as there are many models and the wiring is not all the same. However, if your wiring is different from the OP, does the diagram below represent the reality with your boiler?



If not, if you could post details of what you do have, someone should be able to assist you.

As you are a newbie, for your information, it is better for you to start a new thread with your own question. When you do it will also appear in the 'unanswered threads' section and will be seen more readily by those that can help rather that being hidden at the end of someone else's several months old thread. This is also known as hijacking and against the forum rules.

Don't start a new thread now though, otherwise you will have two threads going on the same subject which can really get confusing.

 

[David Fritty]

Hi Stem,

Sorry about that. Thanks for your help.

I’ll have a look and post a new question with a bit more detail.

 

[pledmonds]

Get some 5 core flex, connect brown to L, blue to N and the green/yellow to earth all on the orange connector.
Remove the two links to the yellow connector.
Connect the black to CH and grey to HW both should have a bit of brown sleeving or tape to indicate that they are live.
Leave the wires in the white connector as they are.
As you say disconnect the ribbon cable to the existing receiver.
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
If you don't want to control the times of the pre-heat then don't bother with the grey wire and leave the link in from L to HW in the boiler.
But you might as well while you are at it to save the boiler coming on at all hours to keep the pre-heat warm.

Sorry for a late thread hijack but I have a question about this - I have pretty much this exact set up and I've followed these instructions and they're working perfectly. HOWEVER I can't find any setting in the Nest to control the hot water pre-heat function - so while it is wired for it, the Nest just never enables it on the boiler. Am I missing something?

Perhaps there's a workaround by telling the Nest that it's working with a system boiler rather than a combi boiler, and setting a schedule for hot water too..? Would that work, and would there be any downsides to doing it, do you think?

 

[stem]

There isn't a 'pre-heat' function per-se. You do use the 'hot water' facility, but setting the Nest to 'combi' will disable the hot water settings, as they are only normally used with stored hot water (ie a hot water cylinder)

 

[modo613]

Hope this isn't seen as a hijack (i'm simply clarifying a point stated earlier). I've found this thread extremely useful, as I've been figuring out how to enable pre-heat control via 3rd gen Nest with five core cable (when the installer managed to use all 5 cores without connecting anything to the Heatlink DHW terminals 4,5,6). Whilst I now understand how this works in principle - I cannot understand the following.

Once the factory fitted link is removed at the boiler between 'Live out' and DHW (aka LR), and the Nest then 'joins' these when DHW is called for, thus when DHW is called for by Nest the boiler will enter pre-heat mode. When DHW is not called for by Nest, the boiler will revert to ECO mode. My question is this - prior the removal of link, if Nest is not connected to this pre-heat terminal, then surely the factory fitted link is creating a permanent link between Live out and DHW - which should cause pre-heat to be permanently enabled?

Is the answer that the boiler simply overrides this by pressing the ECO button, or have I misunderstood the terminal connections?

 

[Johnmdc]

No you have not misunderstand, you are correct. With the link in place pre-heat is switched on and off with the ECO button.