https://www.googlenestcommunity.com/t5/Nest-Thermostats/Geothermal-System/m-p/577086#M114686 <P><a href="https://www.googlenestcommunity.com/t5/user/viewprofilepage/user-id/498309">@brunodigiorgio</a>&nbsp;, When you have a system that uses A+ and B-, you are dealing with equipment that uses a digital, communications system typically based on the RS-485 specifications. &nbsp;Sadly this is not compatible with any conventional thermostat including the Nest. &nbsp;You check to see if your system includes &nbsp;a conventional control system in addition to the digital.</P> <P>AC Cooling Wizard</P> Wed, 17 Jan 2024 18:34:01 GMT CoolingWizard 2024-01-17T18:34:01Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/Geothermal-System/m-p/577012#M114659 <P>Hello Guys! I have a geothermal system in my house, and I'm having trouble installing the next thermostat. I have the wires C, R, A+ and B-. Is it compatible? Thanks!</P> Wed, 17 Jan 2024 15:14:17 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/Geothermal-System/m-p/577012#M114659 brunodigiorgio 2024-01-17T15:14:17Z https://www.googlenestcommunity.com/t5/Nest-Thermostats/Geothermal-System/m-p/577086#M114686 <P><a href="https://www.googlenestcommunity.com/t5/user/viewprofilepage/user-id/498309">@brunodigiorgio</a>&nbsp;, When you have a system that uses A+ and B-, you are dealing with equipment that uses a digital, communications system typically based on the RS-485 specifications. &nbsp;Sadly this is not compatible with any conventional thermostat including the Nest. &nbsp;You check to see if your system includes &nbsp;a conventional control system in addition to the digital.</P> <P>AC Cooling Wizard</P> Wed, 17 Jan 2024 18:34:01 GMT https://www.googlenestcommunity.com/t5/Nest-Thermostats/Geothermal-System/m-p/577086#M114686 CoolingWizard 2024-01-17T18:34:01Z