Smart Thermostat C Wire Explained

Everything you need to know about common wire which you'll certainly need when installing a new smart thermostat in your home. Provided by Jason & David Smarthomelab.net

Transcript

1. Thermostat C Wire: Everything You Need To Know
2. What Is A C-Wire And Why Do You Need One? Traditional HVAC wiring in homes uses four or more wires, one of which is called the “common” wire or c-wire. The basics layout of a typical home wiring system is:
3. • R wire (red, for power). • G wire (green, for a fan). • Y wire (yellow, for air conditioning). • W wire (white, for heat). • C wire (blue or black, common for 24-volt power to the thermostat). • Note that colors may vary and the labeling on systems may be inconsistent
4. The trouble is, the c-wire is not that common in many (older) homes, as a traditional thermostat didn’t require much power. Today’s thermostats come with Wi-Fi connections and high- resolution color touchscreens, demanding more power than older models.
5. They are more likely to require one for this purpose, either to complete the circuit that helps power the smart thermostat or to charge its battery. Those who find their wiring is missing the c wire can use one of the several solutions to power their smart thermostat. Since most brands sell their smart technology without mentioning this on the box, it is easy to find out after you have purchased one.
6. Which Smart Thermostats Don’t Need A Common Wire Some of the leading models on the market can work without a c wire, but only on some HVAC systems, not all of them. These include the: •Nest Learning Thermostat •Nest Thermostat E •Honeywell Lyric Round 2.0. (but requires a c-wire for Apple HomeKit functionality) •ecobee3 •ecobee3 lite •ecobee4 •Sensi Wi-Fi Programmable Thermostat
7. How To Check If You Have A Common Wire The simplest way to check if you have a common wire within your existing wiring is to open up the installed thermostat and take a look. Check for a terminal that has a “c” next to it. If this terminal is connected to a wire, then you have a common wire. In some rare cases, if you can’t see the connections, then you may need to remove the thermostat behind the wall. Check there for a wire running to the “c” terminal to confirm if you have an existing c wire.
8. What To Do If You Don’t Have A C-Wire Adding A C-Wire The best all-round solution is to add a c wire to your home. Use An Add-a-wire Kit Get A Thermostat That Works Without C Wire A Tricky Solution Involves Power Stealing Other solutions include power stealing. This is where the thermostat leaches power from another wire when that’s not being used by the HVAC system and stores it in a battery for the thermostat to use. Using The Fan Wire
9. Made by: Jason Cannon and David Waller