Nest thermostat: existing baseboard heat and new HVAC system

[DavidAlanSmithJ]

Hello, my existing boiler and baseboard heat uses just a Red and white wire to power my thermostat (I do not have a C wire and use a lot of batteries). I am having central air installed and the HVAC guy is telling me I need a Red, Yellow, Green and Common wire to power the AC but the Red slot on my thermostat is already occupied by my heat. How can I fix this? 

[Patrick_Caezza]

Once you have the HVAC system installed you will have two separate systems and only the Nest Learning Thermostat, 3rd Gen is compatible with what is called a dual transformer system.

[DavidAlanSmithJ]

Thanks Patrick. I thought that was the case.

[Ryan_G]

Hi DavidAlanSmithJ,

Thanks for reaching out here in the community.

I'd like to jump in here and check if you still need help with your wiring configuration. If you have further questions, don't hesitate to get back to us.

Thanks for your help, Patrick_Caezza.

Best regards,

Ryan

[Ryan_G]

Hey DavidAlanSmithJ,

I just wanted to follow up and see if you're still in need of help. Please let us know as we would be happy to answer any questions you may have. 

Best regards,

Ryan

[aatienza]

Hey DavidAlanSmithJ,

Chiming in to check if you have additional questions or concerns as we will be locking this thread within 24 hours. 

Let us know so we can assist you right away.

Thanks,

Archie