Wiring Guide: Compatibility & Common Configurations

Introduction

Proper wiring is essential for a successful smart thermostat installation. This guide explains how to identify and connect the right wires to ensure compatibility with your HVAC system.

Understanding Thermostat Wiring

Most smart thermostats use a low-voltage (24V) wiring system. The common wire types include:

Wire Label	Function	Color (Typical)
R	Power	Red
C	Common Wire	Blue/Black
W	Heating	White
Y	Cooling	Yellow
G	Fan	Green
O/B	Heat Pump Reversing	Orange

Identifying Your Existing Wires

1. Turn off power to your HVAC system.
2. Remove the old thermostat cover.
3. Take a picture of the wiring for reference.
4. Label the wires before disconnecting them.

Checking Compatibility

Before proceeding, check:

• If you have a C-wire. If not, your thermostat may require an adapter.
• The thermostat manufacturer's compatibility checker (available online or in the app).
• Your HVAC system type: conventional, heat pump, or multi-stage.

Common Wiring Configurations

1. Standard HVAC System (No Heat Pump)

• R → R terminal (or Rc/Rh if separate power lines exist)
• C → C terminal (if available)
• W → W terminal (heating)
• Y → Y terminal (cooling)
• G → G terminal (fan)

2. Heat Pump System

• R → R terminal
• C → C terminal
• O/B → O/B terminal (controls heat pump reversing valve)
• Y → Y terminal (compressor)
• G → G terminal (fan)

3. Systems Without a C-Wire

If your system lacks a C-wire:

• Use the provided C-wire adapter or a compatible power extender kit.
• Some thermostats allow using the G-wire as a C-wire, but this disables fan control.

Installation Steps

1. Match each wire with the corresponding thermostat terminal.
2. Insert each wire securely into the terminal slots.
3. Attach the thermostat faceplate and restore power.
4. Follow the thermostat’s on-screen setup process.

Troubleshooting Wiring Issues

• Thermostat won’t power on? Ensure the R and C wires are properly connected.
• HVAC system doesn’t turn on? Double-check wiring and ensure the correct system type is selected in settings.
• Error messages? Refer to the manufacturer’s guide for wiring-specific troubleshooting.

Final Checks

• Verify heating and cooling functions by adjusting the temperature.
• Confirm Wi-Fi connectivity and mobile app control.
• Enjoy your smart thermostat with confidence!

For more details, refer to your thermostat’s support documentation or consult a professional if needed.