The only concern is the wire on X terminal. This is a definable contact and we need to know in the programing of the current thermostat when is it activated. The other choice is to go to your indoor unit and take a picture of where the gray wire terminates at.
Ken, The AC Cooling Wizard
Thanks for helping here, Ken.
@Ackear, I hope you've got the answer you're looking for. Have you had a chance to take a photo of your system's control panel? If you're still in need of assistance, feel free to let us know.
I can't figure out how to post photos in a reply so I will describe what I found. It looks like the gray/ brown wire that is connected to the X terminal in the wall thermostat is connected to a brick red wire within the furnace that in turn connects to a C terminal within the furnace. Thank you so much for your help.
I appreciate your effort. Connectors or terminals labeled "X" can represent different things depending on the manufacturer of your thermostat. X connectors are usually labeled as Auxiliaries. But since you were able to figure out on your system that it is C, you might try connecting to the C terminal as well and see if it works.
Feel free to let us know if you have more questions.
@Ackear I'm dropping by to ensure that everything is covered here. How's it going with the wiring set up of your Nest Thermostat? Were you able to perform the steps suggested above? We'd be glad to hear from you — We'd like to make sure everything is working.
I appreciate the help, Mark and Ken.