I had a Nest E installed in February and it has worked really well until it was time to turn on the AC. Now I get random e195 errors (no power detected to the R wire).

The most likely answer from my research is that I need a c wire installed. A friend of mine who's an electrician installed one from the furnace to the Nest. But we are left wondering where to connect the c wire on the furnace. We tried in the "B" terminal but that didn't work.

Would anyone be able to help from the schematics attached?

Furnace Diagram Hi Velocity Control Panel

  • Note in the top right “designates 24v common terminal” and there appears to be 2 choices at the bottom of the diagram. – Tyson Jun 26 '18 at 19:00
  • @Tyson Agreed, but one goes to the AC unit and the other one goes to the Hot Water Valve. Not sure that would do anything for the thermostat? Or am I wrong? – ATN Jun 26 '18 at 19:17
  • @isherwood It's the same as a "regular" Nest, just $100 cheaper or so. I got it for free through a government program. – ATN Jun 26 '18 at 19:17
  • I just noticed a third in the center. And yes they are all electrically “24v common” – Tyson Jun 26 '18 at 19:19
  • @Tyson Let me try that tonight and see if that works. Thanks for your help! – ATN Jun 26 '18 at 19:25

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