C wire possible for Nest thermostat?
I'd get a &quot;piggyback&quot; crimp connector and use that to land the common C wire on the C terminal
Given that your board does not supply outgoing C terminals, we have only one sane place to tap C left, and that's at the terminal where it comes into the board from the transformer.  However, we still need to be able to connect the incoming C wire to that terminal, so you'll need to use a ¼&quot; &quot;piggyback&quot; crimp terminal rated for 18AWG wire crimped onto the end of the common C wire in your panel to leave room to land the C wire from the transformer (it'll look like the one shown below):