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How to wire Google Nest 3rd Gen to this board ? (Australia, 'A' wire, and 'B' wire only)

Community Member


I've a Google Nest 3rd Gen thermostat -

Looking to marry up the 'A' wire, and 'B' wire for my floor central heating system interface, which only has 2 wires ('A' wire, and 'B' wire) both of which are White coloured wires..

The heating system is where a Grundfos pump takes water from a Ferroli gas water heater - when a temperature is reached (Honeywell Thermostat CMT907A controller), for the concrete floor. This is in Australia, 24v system.

Looking at the mapping to the Google Nest 3rd Gen board (Y, G, RC, W1, C, Rh etc..) - am struggling to marry my 'A' and my 'B' to this

• Anyone can support / advise re Google Nest 3rd Gen wiring to the below management (Honeywell Thermostat CMT907A) panel ?

• Which of my white wires goes where in the Google Next 3rd Gen ? 

Much thanks, stuck.



Community Specialist
Community Specialist

Hello ZMacZ,


Thank you for taking the time to let us know about your inquiry. I'd be happy to take a look into this for you.


Wire labels such as 1, 2, 3, 4, and A, B, C, and D indicate a proprietary system. This type of system usually only works with thermostats made by the same manufacturer. But some proprietary systems may also have the option of using standard heating system wires. Consult a local pro to see if your proprietary system can be rewired to work with Nest. Also, here's an article to tell you more about the Nest Thermostat's compatibility.


Please let us know if you have more questions.




Hi folks,

Chiming in to see if you still need assistance with this. Let us know if you have additional questions ― we'd love to help.


Hi everyone,

Just one quick final check in here since activity has slowed down. We haven't heard from you in a while so we'll be locking this thread if there is no update after 24 hours. If you have any new questions, updates or just a discussion topic, feel free to start a new thread in the Community.