This is a new world for me, I haven't messed with circuits since physics 101. When I watched a quick youtube tutorial on setting up my Nest E, I thought it'd be a simple "move wire in old C, to new C in Nest."

But I'm looking at my old thermostat and the instructions said if you have a Rc and Rh thats coupled = dual transformer and not compatible for Nest E. That plus I don't have a wire for W1 (or maybe its broken off??) instead just a wire in W2. Which subsequent instructions stated that W2/O/B should go into the *O/B slot on the Nest. But I doubt that means to put both W2 and O wires into the *O/B slot on the Nest...

Really need some guidance on a dummies explanation for what to do. I was half tempted to just move forward and put wires in best I could, but physics101 warned me not to mess with electricity and improper connections. Some more context, just moved into the apartment. I believe its central Heating and AC. wiring of old thermostat

Old thermostat

**Old thermostat circuit diagram

  • Can you post photos of the wiring at your air-handler/furnace please? – ThreePhaseEel Jun 4 at 2:25
  • Also post the model number and the manual. In the manual it usually tells you which ones to put it in. You did well by taking a picture first. – diy user Jun 4 at 2:26
  • @ThreePhaseEel sorry whats the air-handler/furnace? If thats wiring located on the furnace itself, I won't be able to access it since only maintenace has the keys. I posted a picture, would that be where the wiring is located? – Chris Jun 4 at 2:38
  • @diyuser did you mean the model# for the old thermostat? (Braeburn, 1220NC) Nest is a T4000ES – Chris Jun 4 at 2:38
  • 1
    @ThreePhaseEel not a problem, it just takes a bit, with the pandemic maintenance has been moving a bit more slowly and only really responding to emergency conerns. I'll follow-up after i get back with them – Chris Jun 4 at 12:07

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