Nest compatability with Whalen/Siemens. RAB20U/TWC

[msg822]

We live in a multi-unit condo with the RAB20U thermostats that control both heating and AC. I want to switch to a Nest thermostat but can't determine compatability. There are three main wires (see lThermo ) Y, L, and G3. There is also a 4th wire (blue) that attaches to the terminal block to the right. I'm just trying to determine if the Nest is compatible with this thermostat.

Thanks, Michael

[luciaaa]

Hi, @msg822. 

Thank you so much for consulting in the community. I’m happy to provide you further assistance with your compatibility request.

Based on the pictures you shared, your system is compatible with the Nest Learning thermostat (3rd generation), but this specific installation requires a Nest Pro technician. 

Some heating and cooling systems have fans with multiple speeds. A G3  wire may control either the second or third speed of your system’s fan. The Nest Pro will be able to tell which speed this wire controls.

Keep me posted.

Best regards,

Ana