iDevices Thermostat requires a 24V common or ‘C’ wire, which provides continuous power for features like Wi-Fi connectivity and the backlit display. If the previous thermostat did not have a common wire and used batteries for power or you had a mercury thermostat, there are several options available to connect a common wire. All options require a common terminal at your HVAC control board.
Locating your HVAC control board and identifying the common terminal:
The HVAC control board is where the thermostat wires connect to your heating and cooling system. In most cases the control board can be found at your furnace or air handler. If you’re unable to locate your HVAC control board or are uncomfortable doing so, please contact a certified HVAC technician in your area for additional assistance.
Once you’ve located the HVAC control board, verify there is a common terminal. The common terminal may be labeled C, 24VAC or COMM. Below is a photo a typical HVAC control board with the common terminal circled in red:
Option 1 – Connect an extra wire at the existing thermostat:
Check your current wiring for extra wires the previous thermostat did not utilize. If your HVAC system is compatible, we can use an extra wire as the Common wire. Extra wires may also be tucked behind the thermostat or in the wall, pull gently on the bundle of wires or shine a flash light into the wall to see if any extra wires are present.
If you located an extra wire, we’ll want to ensure the wire is connected to Common terminal at the HVAC control board. Use the steps above to locate the HVAC control board, and identify the common terminal. Connect the same extra wire located at the Thermostat to the Common terminal at the HVAC control board. Once the wire is connected to the Common terminal, turn the breaker on and verify your Thermostat has powered on.
Option 2 - iDevices Thermostat Wire Adapter:
If the current thermostat has at least 3 wires and your HVAC control board has a common terminal, we can use the Thermostat Wire Adapter (https://store.idevicesinc.com/thermostat-wire-adapter/) to power the iDevices Thermostat. The Thermostat Wire Adapter works by running two signal wires for your HVAC system over one wire, freeing up the other to be used as the common wire. Use the steps above to locate the HVAC control board, and identify the common terminal.
Option 3 – Run a new bundle of wires:
Depending on the location of the Thermostat and HVAC system within your home, you may be able to run a new wire bundle with more available wires. Before doing so, use the steps above to locate the HVAC control board, and ensure there is a common terminal. If you’re unsure if running a new wire bundle is the best option for your home, please contact a certified HVAC technician in your area for additional assistance.