Compatible?

[Crhage]

Is this a compatible wiring system? I’m getting conflicting information on the compatibility  site. 

 

[sporfrog]

I think the reason you are getting conflicting responses is because there is no "Common Wire". If you had a common wire it would be connected to the C terminal. It is best to have one.  On some HVAC systems a Nest thermostat will work without one.  On others it can be quirky or not work at all.  

Options:

1. Try it to see if it works without a common.
2. If there is a 5th colored wire in that cable (usually blue or black), it is possible a Common Wire could be connected to HVAC system.
3. Rewire the thermostat with a common wire.
4. Purchase an adapter that creates a common wire.

See this:
https://support.google.com/googlenest/answer/9251212?hl=en