Ideal Logic Combi to Nest 3 connection…

[Flyperson]

Hi,

Merry Christmas to all.

I hope I can enlist the help of some of the kind experts who read these pages. If this post seems familiar I posted something similar a few weeks ago about connecting my boiler to a Hive system. I am now in the process of swapping the Hive for a Nest 3 so my requirements have changed.

I am buying a Nest 3 thermostat system to connect to my Ideal Logic Combi 24. I thought it might be a relatively easy matter as the system is already fitted with a wireless system in the form of the Honeywell CM900 system (to be exact a CM927 system thermostat wirelessly connected to a BDR91 relay box).

Included is an image of the present connections to the present relay receiver box. Two blue leads (neutral) are attached to the N connector and two brown leads (live) are connected to one of the L connectors. I suppose these are from the mains to the boiler via this box.

In addition, a black lead is attached to the connector labelled A and a grey one to connector B. I expect these are for switching the boiler on and off.

From this, could someone please let me know to which of the connectors on the Nest 3 receiver (the Heat Link) I attach these latter two wires (please see included sketch of Nest Heat Link) from connectors 1 to 3? I imagine that the doubled-up neutral and live leads go to the N and L connectors of the Nest receiver as before?

I hope that the other wires visible, but not connected (e.g. the earth leads), in the present relay box remain unattached.

Thanks in advance and if any more information or pictures are required for a diagnosis then please let me know.

 

[stem]

You have worked out that the wires that go to N & L need to remain exactly as they are.

Then if you look at the diagram inside your existing thermostat the switching wires are 'A' which can be seen to be the common (in that it can make contact with both B & C) and 'B' is shown as the call for heat contact, also confirmed by the existing grey wire being connected to it.

So, you simply need to connect them to exactly the same terminals on the Nest. Heating 'Common' (2) and 'Call for Heat' (3)

As you have a combi, you won't be using the hot water functions.

There is an earth terminal on the Nest, so you should put the earth in there.

 

[PullerGas]

Hi,

Merry Christmas to all.

I hope I can enlist the help of some of the kind experts who read these pages. If this post seems familiar I posted something similar a few weeks ago about connecting my boiler to a Hive system. I am now in the process of swapping the Hive for a Nest 3 so my requirements have changed.

I am buying a Nest 3 thermostat system to connect to my Ideal Logic Combi 24. I thought it might be a relatively easy matter as the system is already fitted with a wireless system in the form of the Honeywell CM900 system (to be exact a CM927 system thermostat wirelessly connected to a BDR91 relay box).

Included is an image of the present connections to the present relay receiver box. Two blue leads (neutral) are attached to the N connector and two brown leads (live) are connected to one of the L connectors. I suppose these are from the mains to the boiler via this box.

In addition, a black lead is attached to the connector labelled A and a grey one to connector B. I expect these are for switching the boiler on and off.

From this, could someone please let me know to which of the connectors on the Nest 3 receiver (the Heat Link) I attach these latter two wires (please see included sketch of Nest Heat Link) from connectors 1 to 3? I imagine that the doubled-up neutral and live leads go to the N and L connectors of the Nest receiver as before?

I hope that the other wires visible, but not connected (e.g. the earth leads), in the present relay box remain unattached.

Thanks in advance and if any more information or pictures are required for a diagnosis then please let me know.

View attachment 110974 View attachment 110975

So your doing this job for someone & don't know what you're doing??

 

[Flyperson]

Many thanks Stem for your timely and fulsome reply. The explanation is particularly welcome and is extremely helpful. It's input such as yours that keeps me and friends, who are more accomplished DIYers than me, coming back here for advice. It is, above all, a friendly (usually) place to those who are not experts in its various fields.

Thanks again, and when it comes to the commissioning of my new Nest system I shall be sure to drink to your health Stem.

Kind regards, R.

 

[stem]

You are welcome. I personally like an explanation of why something is, so that I understand it, rather than just an instruction of what I should do. That way we learn for next time.

Old Chinese proverb say: "Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime"

 

[PullerGas]

Old Scottish proverb;
DaftyDIYer feck about with leccy, he gonna get belter that may kill him!!