Two furnace, two a/c units, two thermostats; Control with one 4th gen Nest?

[ayoungtech]

Happy holidays everyone! Here’s my setup:

• Thermostat #1 controls the basement furnace and A/C unit.
• Thermostat #2 controls the upstairs furnace and A/C unit.
• The upstairs thermostat has these wires: Y2(blue), G(green), W(white), C(brown), Y(yellow), R(red) with jumper to RC. 
• I need to check the basement thermostat wiring to confirm, but I think it’ll be the same wires as upstairs. 

I’ve already replaced the upstairs thermostat with a 4th gen Nest w/temp sensor. Basement is still being controlled with the original, not smart, thermostat.     Ideally I’d like to control both the basement and upstairs units with the one 4th gen Nest, but I’m not sure if that’s possible.

• Can I control two separate furnaces and A/C units with one 4th gen Nest?(This would be my ideal setup) I could move the temp sensor to the old thermostat location. 
• If not, can I install an older Nest in the basement and have the upstairs (4th gen Nest) control the basement Nest? (Master-slave style setup)

[maedacortez]

Hi ayoungtech,

Thanks for reaching out. I understand that you want to know if you can: Use one thermostat to control two furnaces and use your older Google Nest Thermostat and the 4th generation to control the older one. I'm happy to assist you!

I apologize, but both features you're looking for are not currently available. the Google Nest Thermostat only can control one furnace, you can connect your Google Nest 4th generation and the older one, but they will work independently.

Let me know if you have any other questions.

Regards,

Manuel