I have a trane TWE040E13FB2 hooked up to a heat pump. I am wanting to install a smart thermostat. Our current thermostat has 10 wires in it. I do not have a common wire. I also don't see a common wire on terminal block in the furnace. Is there a way to hook this up?
Trane is silly
Trane is sometimes silly and calls their C wires B, which is mildly confusing because other brands sometimes use the B designation for the function that your O wire performs, namely heat-pump reversing control. Anyway, you have a perfectly good C wire in disguise as your B wire, so just use that.