Wiring guide
Google Nest Learning Thermostat (4th gen) wiring for rh + Rc dual transformer
This setup is possible with the Google Nest Learning Thermostat (4th gen), but a professional install is recommended.
Wires on both Rh and Rc (not a short jumper between them) mean separate heating and cooling transformers, common with a boiler plus a separate AC air handler. Bridging them can destroy equipment. Read the full rh + Rc dual transformer guide for how to confirm your setup and mistakes to avoid.
Wiring diagram
Detected system: 1-stage heat, 1-stage cooling, fan, no C wire, dual transformer · 5 wires
Google Nest Learning Thermostat (4th gen)
Pro install recommendedGoogle recommends a professional install for dual-transformer (Rh + Rc) systems.
| Wire | Color | Job | Connect to | Note |
|---|---|---|---|---|
| RH | red | Heating power | Rh | |
| W | white | Heat, stage 1 | W | |
| RC | black | Cooling power | Rc | |
| Y | yellow | Cooling, stage 1 | Y | |
| G | green | Fan | G |
Install steps
- Turn off power to the furnace/air handler (switch or breaker) and the AC condenser. Confirm the old thermostat is dead.
- Photograph the old wiring, then label each wire with the letter it came off. Ignore short jumpers.
- Connect each wire to the Nest Learning (4th gen) terminal shown above. Cap unused wires one at a time.
- Restore power and finish setup in the app.
- Test heat, cool and fan. If a breaker trips or equipment runs nonstop, power off and call a pro.
What you need
- Google Nest Learning Thermostat (4th gen)The thermostat itselfCheck price
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Confirm against the official Google Nest install guide. The app also checks your wiring during setup.
Frequently asked questions
Where does each wire go on the Nest Learning (4th gen)?
RH → Rh; W → W; RC → Rc; Y → Y; G → G.
Do I need a C wire for the Nest Learning (4th gen)?
See the notes above for your power options.