The C-Wire provides a continuous flow of power to operate more advanced 24-Volt thermostats and is most often needed when upgrading to Wi-Fi and wireless thermostats. The C-Wire Power Adapter converts existing thermostat wires to common wires (C-Wires) to help make Honeywell Home Smart Thermostats compatible with homes that may be missing this "common" wire. Features easy push terminals and an adhesive mount to attach the adapter to the outside of your furnace, while a closed cover conceals internal components — making installation quick and easy.
Q: Does this adapter have a cover?
A: Yes, it has a closed cover that conceals internal components.
Q: What does the C-Wire Power Adapter do?
A: It converts existing thermostat wires to common wires (C-Wires) to help make Honeywell Home Smart Thermostats compatible with homes that may be missing this "common" wire.
Q: What is the purpose of this device?
A: This device helps power connected thermostats that require a c-wire.
Q: How is the C-wire adapter installed?
A: It has easy push terminals and an adhesive mount to attach the adapter to the outside of your furnace.
A: The C-Wire provides a continuous flow of power to operate more advanced 24-Volt thermostats and is most often needed when upgrading to Wi-Fi and wireless thermostats.
Q: How to lock the wires into a c-wire adapter for a house thermostat.
A: Hi Crashq2u, thank you for reaching out. You have to press the tab of each wiring terminal to insert or remove the wires to or from the adapter. We will be happy to help you checking the wiring. Feel free to contact our tech support team at (800) 633-3991 or send us a Private Message at our Honeywell Home Facebook account. - Maria
Q: how to determine that my system has C wire or not
A: Hi Nunu, thanks for the question. You can determine if your current wiring has a C-wire by checking the thermostat and look for a wire connected to the C-terminal or have a unused wrapped in the bundle. If you don't, you can follow your thermostat wires to the system and see if you have a C terminal available, this is where the adapter is going to be installed.
A: Hi Haggy, this adapter is only compatible with Honeywell Home and Resideo thermostat models.

The C-Wire provides a continuous flow of power to operate more advanced 24-Volt thermostats and is most often needed when upgrading to Wi-Fi and wireless thermostats. The C-Wire Power Adapter converts existing thermostat wires to common wires (C-Wires) to help make Honeywell Home Smart Thermostats compatible with homes that may be missing this "common" wire. Features easy push terminals and an adhesive mount to attach the adapter to the outside of your furnace, while a closed cover conceals internal components — making installation quick and easy.

Make any home an ecobee Smart Thermostat home with the Power Extender Kit (PEK) – a cost-effective and efficient solution for homes without a common wire (C-wire). Not sure if you need a PEK? Visit ecobee.com/compatibility to find out.

Completely customize your Wi-Fi Smart Color Thermostat to match your lifestyle and decor. The ENERGY STAR® certified smart thermostat lets you choose the temperature, schedule, display color and the devices you use to control it all.

Get more control over your comfort with GE CYNC Smart Thermostat. Preset your ideal temperature around your schedule and adjust it away from home through the CYNC app. Turn up the heat or cool down the room from bed using your voice with your Google Home or Amazon Alexa device (sold separately). Set custom schedules in the CYNC app so you can cool the house down before bed and wake up to a warm room. The CYNC Smart Thermostat is compatible with most residential heating and cooling systems. Add CYNC Room Temperature Sensors (sold separately) and set your preferred temperature in the room you are in during different times of the day.
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Work excellent. Instructions are clear and good use of this item.
Posted by JulianC
Works great, fairly easy to install and replaces the mess of wiring.
Posted by
Easy gadget to make ac thermostat work c-wire power adapter
Posted by Assistant1