Is my old thermostat wiring compatible with nest?

[GregB]

 

I have an 18 year old GE thermostat with a brown, red, black, and white wire.   They are not labeled and I don’t see how they line up with the Google Nest thermostat.   Can you help identify these so that I can replace it with the Nest?  Thank you.  

[Houptee]

The wires are under the plate with the mercury bulb. Carefully remove the thermostat some have small screws, and another plastic plate is underneath screwed to the wall with the wires coming thru a hole in the wall connected to the wall plate. 

What type system is this? Heat only or AC also?

You will need a common wire so check if the thermostat cable in the wall has a extra color wire not being used that you can connect as common at the furnace end and at the nest.

Common is needed to keep battery charged up in the nest.

[GregB]

It is heat and AC.  It is a 4T unit with a dual damper.  There is another thermostat just like this upstairs.    I’ll send a picture of the wires behind the plate.  Thank you for your help! 

[rylescu]

When you remove the old GE thermostat, look at the wire connections in the back or on the wallplate. It should tell you the labels -- take a picture before undoing the wires in case you need to put them back. Or you can make your own labels and attach them to the wires so you don't get them mixed up. Remove the wallplate only after you have labeled all the wires and be careful not to let any wire drop into the wall.

If you remove the cover of your furnace and look at the circuit board, it will tell you how the wires in your thermostat are also connected.

[Jeran]

Hey there GregB,

I'm just checking up on this thread, did you have any more questions or need any additional help? 

Thank you for helping out on this thread, Houptee and rylescu!

Best regards,
Jeran
 

[GregB]

Thank you all.  I have not pulled off the back plate yet to look at the wires.   I’ll do that this weekend and let y’all know if I have any additional questions.   Thanks again! 

[Ryan_G]

Hey GregB,

Thanks for being here in the Google Nest Community.

I'd like to jump in here and check if you've already tried looking at the base plate and wires. 

Let us know how it goes by replying to this thread.

Regards,

Ryan

[MelbaDT]

Hi, 

We haven't heard from you in a while so we'll be locking this thread if there is no update within the day. If you have any new issues, updates or just a discussion topic, feel free to start a new thread in the Community.

Best, 

Melba