I recently got a new Honeywell WiFi thermostat, which requires a C-wire. I have 5-wires going to my current thermostat, with only 4 being used. So I thought adding the 5th as my C-wire was going to be easy, but when I opened the furnace panel I saw there was already a wire on C.
I have searched the net for hours, and I have not been able to find anyone with an installation like mine, so I thought I'd ask for some help. I've done my best to trace all the wires, and have created a crude drawing (attached). There are splices in a few places, due to the humidifier, and the outside unit is spliced in between the furnace C and the thermostat Y in between the joists above the furnace. This is the part that is really throwing me for a loop, along with the Y terminal on my furnace being empty. Based on what I have been learning while surfing around, I'm not understanding how it's currently working (which makes me hesitant to change anything). And yes, it currently works!
I would appreciate any thoughts you can share.