I have a Honeywell THX9421R5021WW. It does use wifi. It only has 2 wires R and C. The C wire is white and seems to be powering the thermostat. The R wire is red. I want to replace it with a nest 3rd gen. Is this possible. Thanks.
Based on the wiring, it looks like your system is proprietary. Proprietary systems are not compatible with Google Nest thermostats. However, some proprietary systems can be rewired by a Nest Pro installer to be compatible.
