I have a Trane XV80 with a 2 stage motor. I'm replacing a Trane TCONT803AS32DAA thermostat with a Honeywell wifi thermostat thinking it would be an easy switch out. However, the older thermostat had 5 wires; Red = "R" with an "RC" jumper, Yellow = "Y", Green = "G", White = "W1", Blue = "W2".
The Honeywell instructions said to use the Green as "C", then on the furnace control box change Green from "G" to "C" and jumper the "Y" and "G". But the furnace control has a white wire coming from "B/C", make 2 white wires coming from the furnace. All of the other wires seem to correspond with the thermostat wiring.
Any idea on what happened to the "B/C" wire from the furnace? It is not in the wrapped wire bundle hidden in the wall behind the old thermostat? Do I just need to run another wire directly from the furnace "B/C" to "C" on the thermostat?