Wiring guide
Amazon Smart Thermostat wiring for rh + Rc dual transformer
The Amazon Smart Thermostat is not compatible with this setup. See the alternatives below.
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
Amazon Smart Thermostat
Not compatibleSeparate Rh and Rc wires mean two transformers, which the Amazon Smart Thermostat doesn’t support.
| Wire | Color | Job | Connect to | Note |
|---|---|---|---|---|
| RH | red | Heating power | Don’t connect | No matching terminal on the Amazon Smart Thermostat |
| W | white | Heat, stage 1 | W | |
| RC | black | Cooling power | Don’t connect | No matching terminal on the Amazon Smart Thermostat |
| 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 Amazon Smart Thermostat 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
- Amazon Smart ThermostatThe thermostat itselfCheck price
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Confirm against the official Amazon install guide. The app also checks your wiring during setup.
Frequently asked questions
Where does each wire go on the Amazon Smart Thermostat?
RH → not connected; W → W; RC → not connected; Y → Y; G → G.
Do I need a C wire for the Amazon Smart Thermostat?
Separate Rh and Rc wires mean two transformers, which the Amazon Smart Thermostat doesn’t support.