Cielo Smart Thermostat is fully compatible with dual-transformer systems, but the wiring and setup process is a little different compared to single-transformer installations.
First, confirm that your HVAC setup is a dual-transformer system, and then follow one of the installation methods below to complete the setup.
How to Confirm that You Have a Dual Transformer System?
On most thermostats, a jumper connects the Rc and Rh terminals on the base, with only one R wire running behind the wall. If there is only one R wire (that includes R, Rc, & Rh), you do not have a dual-transformer system. In this case, simply follow the standard installation guide for your Cielo Smart Thermostat.
A dual-transformer system will have two separate R wires coming from the wall - one connected to Rc (cooling) and the other to Rh (heating).
Before you begin
- Double-check wiring at your HVAC equipment. In some cases, two R wires from the thermostat may connect to the same terminal in the system. This means you actually have a single transformer system, and the second R is unused.
- Do not install jumper wires on your Cielo Smart Thermostat. If only one R wire (that includes R, Rc, & Rh) is present, connect it to the Rc terminal.
- Once you’ve confirmed that you have a dual-transformer system with two R wires, choose one of the installation options below. These options are listed in order of ease of installation.
⚠️ Warning: The Cielo C-Wire Adapter (CWA) is not compatible with dual-transformer systems. Installing it in a dual-transformer setup may damage your HVAC system.
Standard Setup vs. Dual-Transformer Setup
- Single R-wire system: One R wire (that includes R, Rc, & Rh) is present.
- Dual-transformer system: Two separate R wires (Rc and Rh) come from the wall, each powered by a different transformer (one for heating, one for cooling).
Install a Cielo Smart Thermostat with a Dual-Transformer System
Cielo Smart Thermostats are fully compatible with dual-transformer systems. However, the installation is different from a standard installation, and care must be taken to ensure correct wiring.
Installation Options
Once you’ve confirmed you have a dual-transformer system, you can install the Cielo Smart Thermostat using one of the following methods. Start with Option 1 and move to Option 2 if needed.
Option 1: Install Using a C-Wire (Recommended)
⚠️ Warning: The Cielo C-Wire Adapter (CWA) is not compatible with dual-transformer systems. Using it can damage your HVAC equipment.
Use this option if:
- You already have a C-wire from the cooling bundle, or
- You have an unused spare wire in the cooling bundle that can be used as C, or
- You can run a new wire between the thermostat and the cooling system
The C-wire (common wire) provides a continuous 24V power supply required for your Cielo Smart Thermostat.
How to Verify the C-Wire
1. Label Your Already Installed Wires
Turn off power to your HVAC system and use the labels provided with your Cielo Smart Thermostat to mark each wire. Once you've labelled the wires, take a photo of the wiring for reference.
2. Inspect Wires Behind the Thermostat Base
Once you have labelled the wires, disconnect them from the base of your thermostat to carefully inspect the wiring inside the wall. If necessary, remove the thermostat base for a better view.
For dual-fuel transformers, you'll typically find two separate wire bundles:
- Cooling bundle: Rc, Y, G
- Heating bundle: Rh, W1
Identify which wires belong to the cooling side.
3. Check for a C-Wire on the Cooling Side
- If your old thermostat already has a C-wire, confirm that it comes from the cooling bundle (the one with Rc, G, Y wires). If so, simply connect this wire to the C terminal of Cielo Smart Thermostat.
- If no C-wire is present, look for any extra unused wires in the cooling bundle. You can use one of these as the C-wire (ensure it is also connected to the C terminal on the air handler control board).
- In case there is no spare wire, you will need to run a new wire between the air handler and the thermostat to complete the connection for C-wire.
Option 2: Repurpose the G-Wire as the C-Wire
Use this method only if:
- You don't have any C-wire present in the cooling bundle,
- No spare wires are available in the cooling bundle to repurpose as C-wire, and
- You are okay with losing independent blower fan control
You can repurpose the G-wire (fan wire) as the C-wire (common wire) by moving it to the C terminal on both the thermostat and the air handler. This provides the necessary continuous power for your Cielo Smart Thermostat.
Steps to Repurpose the G-Wire as C-Wire
- Before repurposing the G-wire as the C-wire, make sure to power off your HVAC system and ensure that no air is coming out from the air vents.
- Go to your air handler control board and disconnect the wire from the G connector.
- Attach the G-wire from the air handler control board to the C terminal on air handler control board.
- Install a jumper wire between the Y and G terminals on the control board. This will ensure that your fan switches ON each time your turn ON the cooling.
- Now go back to Cielo Smart Thermostat and connect the former G-wire to the C terminal on the Cielo Smart Thermostat. Connect the remaining wires to their relevant terminals.
- While setting up your Cielo Smart Thermostat, manually enter the G-wire as the thermostat cannot automatically detect the G-wire when it is only connected by a jumper.
Testing the HVAC System
After completing installation, it is advised to test both heating and cooling using the test equipment feature of Cielo Smart Thermostat.
- Cooling Test: Confirm that the outdoor A/C unit and indoor blower fan turn on and cold air flows through the vents.
- Heating Test: Ensure your furnace or heating system starts correctly.