Smart thermostat C wire (common wire) for Lennox CX34 30b

hamlett22

I need a common wire 24v for a new smart thermostat I want to put in as a replacement for an old failing thermostat. There is one extra black wire in the thermostat wiring bundle running to my current 20 year old non-smart thermostat which is using 4 wires (red, white, yellow and green). The unused black wire is wrapped around the bundle of wires behind the mounting plate. That black wire is available downstairs within the same bundle of wires under the furnace logic board.

My home HVAC is a Lennox CX34 30b furnace with an exterior AC unit and an AprilAir whole house humidifier. Currently, the C terminus on the furnace logic board has TWO (2) wires connected to it: one to the humidifier and one to the AC unit. None of the wires from the thermostat wire-run are connected to the C terminus.

Question- can I connect that black wire to the C terminus along with the other 2 wires currently connected to it? Just want to make sure that is feasible given that there are already two wires using that C terminus.

Thanks

GW

Yes land that black one on C. You’re lucky you have an extra wire