The white wire underneath your thermostat connects to your heating system. It terminates at your air handler or furnace. The white wire connects to terminal W in industry-standard thermostats.

Where do thermostat wires run to?

If your system has a C-wire, it might be in use or just tucked away behind your current thermostat. If your system doesnt have a C-wire, youll need to run a new cable from your furnace to your thermostat to install most of the modern smart thermostat models.

How do you wire thermostat wires to a thermostat?

5:4611:06Basic Thermostat Wiring - YouTubeYouTubeStart of suggested clipEnd of suggested clipSuggested clip · 59 secondsInto the W terminal and the green wire into G or the fan tighten that one up as well. Okay. So weMoreInto the W terminal and the green wire into G or the fan tighten that one up as well. Okay. So we have the thermostat hooked up and then of course this wire goes into the wall and down to the furnace.