2-Stage Gas Furnace

[lmsarmento]

hi there,

I recently replaced my old furnace with a new 2-stage furnace heater, and I'm looking for guidance on how to wire it properly to my new Nest thermostat.

I have a picture showing the current wiring (but don’t know to attach it here), along with three unused wires. I want to ensure that I'm connecting everything correctly so the 2-stage heating functions as intended.

Could you provide the correct wiring diagram or advice on how to proceed?

thanks

[lmsarmento]

and here’s the current wiring (please note that I’ll update to Nest learning)

 

 

[jenniffert]

Hi lmsarmento,

Thank you for posting in the community! I'm happy to help you with installing the 2-stage heating wire on your Nest thermostat.

I appreciate the details you've shared. Based on the information you've provided, I want to confirm if you want to know how to install the other three wires on your new Nest Learning thermostat. If so, I'd appreciate it if you could share a picture of the initial installation or the furnace control board. This will help me better identify where the three wires need to be installed on the Nest Learning thermostat and their functions.

Regarding the 2-stage gas furnace, the Nest Learning thermostat has a specific terminal for connecting it: "W2 (2-stage heating)". For reference, you can check out this article: Identify a thermostat wire.

Please keep me posted.

Best regards,

Jenniffer

[lmsarmento]

Hello,

thanks for your help.

This is the picture of my furnace’s control board. Apparently there’s no wire connected to the W2. Not sure if it’s because it’s a brand new furnace and they are able to run 2-stages just using W1.

Appreciate any suggestions.

Thanks

 

 

[maedacortez · Accepted solution]

Hi lmsarmento,

Thanks for your picture. As you mentioned, your system is a 2-stage gas furnace. In this case, you'll need to connect two wires to the Nest Learning Thermostat for it to work with both stages (W1 and W2).

I recommend contacting your personal technician to verify if there's an option to connect the W2 wire on your new HVAC system. The Nest Learning Thermostat will require W2 to function properly with a 2-stage gas furnace.

Regards, 

Manuel