Installing a 3rd generation Nest thermostat is a smart move for homeowners who want to control their HVAC system more efficiently. It is easy to install, and with the right Nest thermostat wiring diagram, you can do it yourself.
Before digging into the details, you need to know that there are two types of HVAC systems: conventional and heat pumps. This article will guide you through the Nest thermostat wiring diagram for both conventional and heat pump HVAC systems.
Conventional HVAC System
A conventional HVAC system uses separate wires to control the heating and cooling systems. Here’s how the Nest thermostat wiring diagram should look like for a conventional HVAC system:
| Wires | Nest Terminal | Description |
|---|---|---|
| Rh, Rc | Rh | Power from the heating and cooling system transformer |
| W1 | W1 | Heating control signal |
| Y1 | Y1 | Cooling control signal |
| G | G | Fan control signal |
Make sure to turn off the power to your HVAC system before installing the Nest thermostat. Depending on your wiring setup, you may need to connect a jumper wire between Rh and Rc terminals on the Nest thermostat.
FAQ
Q: What if my HVAC system uses a C wire?
A: The C wire is not required for a Nest thermostat to function, but it can provide a more stable power source. You can connect the C wire to the Nest thermostat’s C terminal if you have one. Otherwise, you can use the Nest’s power-stealing feature to draw power from your HVAC system.
Q: What if I have a two-stage heating or cooling system?
A: If your HVAC system has a two-stage heating or cooling system, you can connect the second-stage wires to W2 or Y2 terminals on the Nest thermostat. Refer to the Nest thermostat installation guide for more information.
Heat Pump HVAC System
A heat pump HVAC system uses a different wiring setup than a conventional system. Here’s how the Nest thermostat wiring diagram should look like for a heat pump HVAC system:
| Wires | Nest Terminal | Description |
|---|---|---|
| Rh, Rc | Rh | Power from the heating and cooling system transformer |
| W1, Y1, G | W1, Y1, G | Control signals for the heating, cooling, and fan systems |
| O/B | O/B | Control signal for reversing valve |
| Aux/E | Aux/E | Heat auxiliary or emergency heat relay control signal |
Make sure to follow the Nest thermostat installation guide and the HVAC system’s wiring diagram. The O/B wire will determine if your HVAC system is switching between heating and cooling. If it is a heat pump, you need to set the O/B to “O” or “B” depending on the brand.
FAQ
Q: What if my heat pump system has a C wire?
A: If your heat pump system has a C wire, you can connect it to the Nest thermostat’s C terminal. If it doesn’t, you can use the Nest’s power-stealing feature to draw power from your HVAC system.
Q: What if I have a two-stage heating or cooling system?
A: If you have a two-stage heating or cooling system, you can connect the second-stage wires to W2, Y2, or Aux/E terminals on the Nest thermostat. Refer to the Nest thermostat installation guide for more information.
Conclusion
With the Nest thermostat wiring diagram, you can easily install and configure your 3rd generation Nest thermostat. Remember to turn off the power to your HVAC system before installing the Nest thermostat. Follow the installation guide and the wiring diagram to ensure a successful installation.
