Honeywell RTH9580WF Smart Thermostats generally use the same wire labeling as their older models. Through this wire, it gets its 24 volt AC power for running its WiFi, internet, and program functions. Upgrade from non-programmable model that not use the C wire, then you may have to improvise. Most thermostats nowadays detach from a wall mounting plate. This allows simple wire hookups, with low risk of thermostat damage. Wire labels will be most helpful when wiring the new wall plate for our Honeywell RTH9580WF Smart WiFi Thermostat. Look for unused conductors (single wires) in your existing thermostat cable. Often, installers [...]