Before setting up your Cielo Smart Thermostat, it's important to understand wiring configurations for a smooth installation process. Outlined below are detailed wiring diagrams that illustrate common system configurations. These visuals can help you identify wire functions.
Most HVAC systems fall into three main categories:
- Conventional heating/cooling systems i.e., furnace, a boiler & central air conditioner.
- Heat pump systems.
- Dual fuel systems that use both an electric heat pump and a gas furnace.
A thermostat base typically includes 4 to 16 terminals, depending on the system type and the features supported by the thermostat. While these terminals are usually labeled, the lettering may vary slightly between manufacturers. Still, some commonly accepted conventions can serve as a guide.
📢 Note: Not all terminals will necessarily have wires connected to them. The ones you'll use depend entirely on your specific HVAC configuration.
Cielo Smart Thermostat Works With Over 95% HVAC Systems
| System | Equipment | Stages |
|---|---|---|
| Supported Systems (Residential 24V AC) | ||
| Dual Fuel System | All types of Furnaces / Boilers + Heat Pumps | Supports up to 4 stages of heating (2 stages heat pump, 2 stages auxiliary heat) and 2 stages of cooling |
| Heat Pumps | All types of Heat Pumps | Supports up to 2 stages of heating and 2 stages of cooling |
| Conventional Heating | All types of Boilers (radiant in-floor or free-standing “heat-only” system) | Supports up to 2 stages of heating |
| All types of Furnaces | Supports up to 2 stages of heating | |
| Conventional Cooling | All types of Air Conditioners | Supports up to 2 stages of cooling |
| Conventional Heating and Cooling | All types of Furnaces / Boilers + All types of Air Conditioners | Supports up to 2 stages of heating and 2 stages of cooling |
| Humidifier/Dehumidifier | All types of whole-home humidifiers & dehumidifiers | Supports control of one 1-wire or one 2-wire humidifier/dehumidifier |
To check if your system is compatible with Cielo Smart Thermostat, you can visit compatibility checker.
Common Wiring Configurations for Cielo Smart Thermostat
Cielo Smart Thermostat is compatible with a wide range of HVAC systems, each with its own wiring setup. The diagrams below illustrate the most common wiring layouts. You can use them as a reference to identify which configuration matches your system when installing the Cielo Smart Thermostat.
Supported Wiring (Cielo Smart Thermostat)
Conventional Heating/Cooling Systems | |
|---|---|
| Label | Function |
| Y1 | Stage 1 Compressor Relay (Cooling) |
| Y2 | Stage 2 Compressor Relay (Cooling) |
| G | Fan Relay |
| O/B | Not Used |
| Rc | 24VAC Power from (Cooling) Transformer |
| W1 | Stage 1 Heat Relay |
| W2 | Stage 2 Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from (Heating) Transformer |
| CWA |
|
Heat Pump Systems | |
|---|---|
| Label | Function |
| Y1 | Stage 1 Compressor Relay (Cooling) |
| Y2 | Stage 2 Compressor Relay (Cooling) |
| G | Fan Relay |
| O/B | Controlling the Reversing Valve in a Heat Pump System |
| Rc | 24VAC Power from (Cooling) Transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from (Heating) Transformer |
| CWA |
|
*No jumper wires required. You don't need to hang on to old jumper wires going from Rh (sometimes just called R) to Rc.
Conventional 1 Stage Heating
Required wires: W1, Rc, C, G (G optional)
Conventional 1 Stage Heating
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC Power |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
- Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating.
- C-wire adapter does not work with heat-only systems, dual transformer systems, fan coil, and communicating units.
Conventional 2 Stage Heating
Required wires: W1, W2, Rc, C, G (G optional)
Conventional 2 Stage Heating
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC Power |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
- Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating.
- C-wire adapter does not work with heat-only systems, dual transformer systems, fan coil, and communicating units.
Conventional 1 Stage Heating, 1 Stage Cooling
Required wires: W1, Y1, Rc, C, G (G optional)
Conventional 1 Stage Heating, 1 Stage Cooling
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC Power from Cooling Transformer |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating & cooling.
Conventional 2 Stage Heating, 1 Stage Cooling
Required wires: W1, W2, Y1, Rc, C, G (G optional)
Conventional 2 Stage Heating, 1 Stage Cooling
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC Power from Cooling Transformer |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating & cooling.
Conventional 2 Stage Heating, 2 Stage Cooling
Required wires: W1, W2, Y1, Y2, Rc, C, G (G optional)
Conventional 2 Stage Heating, 2 Stage Cooling
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC power from cooling transformer |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating & cooling.
Conventional 1 Stage Heating, 2 Stage Cooling
Required wires: Y2, Y1, Rc, C, W1, G (G optional)
Conventional 1 Stage Heating, 2 Stage Cooling
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC power from cooling transformer |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating & cooling.
Conventional 1 Stage Cooling
Required wires: Y1, G, C, Rc, G (G optional)
Conventional 1 Stage Cooling
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC Power from Cooling Transformer |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC Power from Heating Transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo
Smart Thermostat
will not be able to control the fan independently of cooling.
Conventional 2 Stage Cooling
Required wires: Y2, Y1, G, Rc, C, G (G optional)
Conventional 2 Stage Cooling
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Not used |
| Rc | 24VAC power from cooling transformer |
| W1 | Heat Relay (Stage 1) |
| W2 | Heat Relay (Stage 2) |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo
Smart
Thermostat
will not be able to control the fan independently of cooling.
1 Stage Heat Pump
Required wires: Y1, O/B, Rc, C, G (G optional)
1 Stage Heat Pump
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Heat Pump Changeover Valve |
| Rc | 24VAC power from cooling transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of cooling.
1 Stage Heat Pump with Aux Heat
Required wires: Y1, O/B, Rc, C, W1, G (G optional)
1 Stage Heat Pump with Aux Heat
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Heat Pump Changeover Valve |
| Rc | 24VAC power from cooling transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo
Smart
Thermostat
will not be able to control the fan independently of heating
&
cooling.
2 Stage Heat Pump
Required wires: Y1, Y2, O/B, Rc, C, G (G optional)
2 Stage Heat Pump
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Heat Pump Changeover Valve |
| Rc | 24VAC power from cooling transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of cooling.
Dual Fuel - 2 Stage Heat Pump, 1 Stage Heat
Required wires: Y2, Y1, W1, C, O/B, Rc, G (G optional)
Dual Fuel - 2 Stage Heat Pump, 1 Stage Heat
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Heat Pump Changeover Valve |
| Rc | 24VAC power from cooling transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
|
* Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating & cooling.
Dual Transformer Systems - 1 Stage Heat Pump, 2 Stage Heat
Required wires: Y1, O/B, Rc, Rh, C, W1, W2, G (G optional)
Dual Transformer Systems - 1 Stage Heat Pump, 2 Stage Heat
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Heat Pump Changeover Valve |
| Rc | 24VAC power from cooling transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
Not used |
- Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating.
- C-wire adapter does not work with heat-only systems, dual transformer systems, fan coil, and communicating units.
Dual Transformer Systems - 2 Stage Heat Pump, 2 Stage Heat
Required wires: Y1, Y2, O/B, Rc, Rh, C, W1, W2, G (G optional)
Dual Transformer Systems - 2 Stage Heat Pump, 2 Stage Heat
| Label | Function |
|---|---|
| Y1 | Compressor Relay (Stage 1) (Cooling) |
| Y2 | Compressor Relay (Stage 2) (Cooling) |
| G | Fan Relay (Optional) |
| O/B | Heat Pump Changeover Valve |
| Rc | 24VAC power from cooling transformer |
| W1 | Stage 1 Aux Heat Relay |
| W2 | Stage 2 Aux Heat Relay |
| C | 24VAC Common Wire |
| Rh | 24VAC power from heating transformer |
| CWA |
Not used |
- Fan Relay (G) is optional. However, without a G-Wire, Cielo Smart Thermostat will not be able to control the fan independently of heating.
- C-wire adapter does not work with heat-only systems, dual transformer systems, fan coil, and communicating units.
Important Wiring Considerations
- Ensure all the wires are fully installed into the Cielo Smart Thermostat. For ease of insertion press the terminal block buttons.
- If your system has only one of the following R-wires (that includes R, Rc, or Rh wire) insert it into the Rc terminal.
- If your system has two R-wires (Both Rc & Rh), insert the Rh wire into the Rh terminal and Rc or R wire into the Rc terminal.
- Some HVAC systems have a safety switch that cuts power if the cover panel is not closed. Make sure the cover panel is properly secured.
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