Help! Google Nest 3rd Generation Thermostat

[Dbarfoot]

I am installing a Nest 3rd Generation where I had an older battery powered thermostat. The Wires I have are RC (Black), RH, (Red) Y (Orange), G (Blue), W/E  (White). When I go down to my furnace I have a G wire, (Blue) an R wire (Black), a Y wire (Orange). Then I have a split wire that goes to my A/C unit outside, it taps into the Y (White) and C (Black) ports on my furnace. I then have the White and Red Wires that come from the thermostat that are then maretted to another split wire coming from the motor of my furnace (red on black, white on white) 

Is there a way to attach the Nest without using a C wire? Or could I move my Red or White wires that are marretted into one of the other ports to replace it (ex. Move the black wire from R to C and then attach the Red wire to R?) 

Thank you! 

Thermostat connection 

Furnace Connection 

[Markjosephp]

Hello Dbarfoot,

It appears you've got a bit of a wiring puzzle, but don't worry; we can figure this out. The Nest Thermostat typically requires a C wire for power, but there are a few options for installation without one.

One solution is to use the G wire as a C wire. Since your furnace has a G wire (blue), you can connect that to the C terminal on your system's control board and Nest Thermostat. Then, connect the other wires as follows:

• RH (red) to R on the Nest Thermostat.
• RC (black) to Rh on the Nest Thermostat.
• Y (orange) to Y on the Nest Thermostat.
• G (blue) to G on the Nest Thermostat.
• W/E (white) to W1 on the Nest Thermostat.

By repurposing the G wire as a C wire, you should be able to power your thermostat without needing an additional wire. Remember to turn off the power before making any changes to the wiring, and proceed with caution. If you're unsure or uncomfortable with the process, it's always a good idea to seek professional assistance.

Best regards,
Mark