Google nest learning 3rd generation thermostat

[Sweetbobbbby13]

Hello I moved to a house where the old owner has set up three zones thermostats, one in the basement, one in the upper floor and two in the middle floor one for heating and one for cooling in the middle floor.

what do I have to do to install the nest learning thermostat on the middle floor? Should I combine the two thermostats to one nest thermostat and how should I connect the common wire? The two thermostats one for cooling has three wires connected to Y, G & RC and one for heating has only two wires connected to W & RC, can anyone kindly please advise me how to connect them and should I connect to the common wire and which wire should I use as the common wire?

The other question I have can I combine the other thermostats to a one thermostat?

Thank you!

[zoeuvre]

Hi Sweetbobbbby13, 

Thanks for posting here in the Community forum and for showing interest in our Nest Thermostats. 

You may install a Nest Learning Thermostat 3rd generation for your separate heating and cooling system, which is a dual-fuel system. The common wire can only be installed if there is a common wire already presented to your current thermostat, or you can identify one from your control board. Also, you can only use one Nest Thermostat per system unless the system is a dual-fuel system that a Nest Learning Thermostat can cater to. If you have other thermostats that you want replaced by a Nest thermostat, then you have to install one Nest thermostat per system only.

On the other hand, to help us get a better picture of what's happening, do you mind sharing a photo of your thermostats and the zone board? Kindly label them so I can easily identify them as well. You may also view this link of Nest Thermostat Compatibility for more. 

Keep us posted. We're happy to help.

Best,

Zoe