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enter image description hereMy current thermostat is wired as follows and the wires are from my Separate heater and separate AC air handler:

W - From my heat R - From my heat

Rc - From my AC Handler Y - From the compressor G - From the AC Handler

Do I need to add a wire for the C connection but am unsure whether I need to do that how and where to connect it. Our can I do something else with the G wire? I have attached a pi of my current schematic, can anyone please help?

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  • Do you have a spare wire in the cable between your air handler and your thermostat?
    – ThreePhaseEel
    Commented Jan 18, 2019 at 1:14

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In the picture below you can note that the connection labeled with a 7 in a triangle is the "C" of your fan controller. As per your added note to the diagram this is also connected to your A/C unit so there is a common "C" between your A/C and the fan controller. This same place is where you want to connect a spare wire to run for the "C" terminal on your thermostat.

enter image description here

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  • Oh, the reason I have posted this is because I want to install a Honeywell 9000 Wifi thermostat and it needs a "C" wire. I had seen a few Youtube videos about alternate ways to add a "C" wire so I didn't know if I could just connect to the "C" at the 7 (which is on a wire nut above my AC air handler).
    – Dave S
    Commented Jan 19, 2019 at 15:34
  • @DaveS - You ask again where to connect for the thermostat. Yet I already said where in my answer.
    – Michael Karas ♦
    Commented Jan 24, 2019 at 1:47

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