Installing an ecobee4 thermostat. Have a 2 stage furnace with ac. Had a Trane furnace installed couple years ago and just noticed it's jumpered between W1-W2. Old thermostat wire was only 4, apparently HVAC guy didn't want to pull a new one and just did this for the timed second stage. I will be running new wire and want it to run truly 2 stage. Question I have upon looking at everything is as I understand it the Y should be connected from thermostat, furnace control board, and outdoor ac unit. And the other ac wire connected to the B/C on the furnace, which is also going to be connected to the new ecobee. This isn't how it currently is though. Currently the Y on the thermostat goes directly to the other wire on the ac unit not connected to B/C. Furnace board has no Y connected to it. Now everything works fine, ac in summer has been fine. Is this how I should run the new ecobee4? Does the Y on the furnace not need to be used? Thanks.
Most all the newer furnaces there will be a 'Y' terminal at the furnace. However, this 'Y' terminal does nothing at the furnace location. On the board, it is a connection point only. Essentially, the Y signal originates at the thermostat, travels on the yellow wire, passes straight through the furnace out to the starting contactor at the A/C condenser. That contactor at the condenser also needs the B/C from the furnace. These High tech thermostats will also need a common, B/C wire as well as the normal control wires.