Will Nest Work with Lennox?

Nest is not compatible with Lennox XC21. It has 2 stage cooling and the Nest will not be able to activate 2nd stage due to protocol issues.

Is Nest compatible with all AC units?

Google Nest thermostats are designed to work with most 24 V systems, even older systems. They work with all common fuel types including natural gas, oil, and electricity. The app will also give you a custom wiring guide for your thermostat. ...

Is Nest compatible with Trane?

The Nest is compatible with about 95% of all heating and air conditioning systems on the market. ... Trane's ComfortLink II can also control just about any HVAC system's temperature, but to get the most out of it, you'll want to hook it up to compatible Trane products.