We installed a programmable thermostat last night. What would probably have been a half hour installation for the average handyman was, of course, a 3 hour nightmare for me. The handyman incompetence field I emit was in full effect. Screw blue wire into contact. Blue wire falls out. Screw blue wire into contact. Blue wire falls out. Screw blue wire into contact. Blue wire falls out. You begin to get the idea. Wire colors didn’t match what the manual said. Wire types didn’t match. New thermostat has a contact for the C wire, but no mention of it in the manual. Didn’t seem to do anything. I learned that our old thermostat was plugged into the phone line I assume for remote setting. Too bad you practically had to put your thumb through the old one to get the buttons to respond. Well, I learned a bit about thermostats, which I’ll probably forget by the time I need to install another one. The best part is that it didn’t start an electrical fire yet.
[For my future reference, here are some lessons learned. Take a picture of old contacts before you start. Ignore wire colors and go by previous thermostat connections. Several experiments finally taught us we needed to configure it as a 4-wire installation with AC and heat power connected together. The brown C (common) wire was connected to old thermostat, but is unused in new one because it has batteries. Green wire seems to be nothing.]