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Discussion Starter · #1 ·
Hello,

I am trying to install a lyric T5 smart thermostat and it requires a "C" wire. my current setup is as shown in the attached picture. I have a wire ran to O, G, Y, Rh and a jumper from Rh to Rc. I have two additional wires (one white and one orange) bundled up and left unconnected in the wall. after trying to connect both of those unused wires as the "C" wire with no luck i went up on the roof to my heat pump to check it out. popped the cover on my heat pump (a trane WCC042F100BB. the 2nd and 3rd attached pics.) the orange and white wires are bundled up in the unit not connected to anything. I am hoping it is as simple as connecting one of the two unused wires and making them the "C" wire. however; i didn't see any terminals labeled "C" on the unit. i have not been able to find a manual online anywhere for my unit. does anyone have any idea if i can somehow make a "C" wire connection somewhere on my unit or it is just too old? (2005). please help! thanks
 

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Yes that'll work.

Use the orange and connect it to the side of the transformer that's connected to the chassis. (it'll be with a green grounding screw.)

Cheers!
 

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Discussion Starter · #3 ·
sorry still a bit of a newbie. which one is the transformer? is it the one labeled 1 or 2 in the attached pics? and all of the connections look like much larger gauge wiring. can i connect the 18g thermostat wire directly to the transformer by stripping the insulation and using a similar connector as the others connected to the transformer?
 

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None of those are transformers. 1 and 2 are relays. But it looks like the blue on the relays will be your common (C wire). You can attach anywhere on the blue line.
 
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