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I am looking to upgrade from an old analog tstat to a Nest. My old stat had only two wires connected (R and W) but the wire bundle had three. So I tried connecting the green wire to C and then turned the power on. Nothing happened, so I switched the green and white just to make sure it was the wire that was the issue. Still nothing. I will admit that I’m a novice, but I really thought this would work. What am I missing?

Heater is a Goodwin.

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  • Nest can work with two wires only (it will cycle Rh to draw power to recharge the battery), in most cases it work just fine. Anyway you should check the green continuity (use green as red and see if works.) – DDS Oct 8 '18 at 21:54
  • What does the compatibility wiring diagram say on the Nest website? I have never seen a WiFi thermostat that works on just 3 wires. What I have read is you need 4 wires. – Jeff Cates Oct 8 '18 at 22:03
  • Do you have A/C as well? – Jeff Cates Oct 8 '18 at 22:03
  • I do not have AC. I checked their comparability website and it said it could actually work with just two (Rh and W). I’m gonna give this another try. – Chris Oct 8 '18 at 22:23
  • @JeffCates you are assuming the thermostat has fan control or A/C. Heat-only furnaces without fan control are only 2 wires, R and W. Nest adds one more, C, and powers itself between R and C. – Harper Oct 8 '18 at 22:26


I apologize for wasting your time. I feel like an idiot. It was because I didn’t put the face plate back on the heater and the kill switch was on. My bad! Sorry again.

  • Glad it was something simple! – ThreePhaseEel Oct 8 '18 at 22:55

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