You sacrifice some energy savings by switching from the Trane Tstat. Is it the comfort link? If so it uses proprietary info to communicate with the control board in the furnace/ac. I ran into this last summer. We put in the See Touch Lutron Tstat anyway. It integrated with the existing HVAC system on Lutron, and the 40 loads of lighting. stupid to have to use a different app for one HVAC system in your house.