I Want a Smart Thermostat but Don't Have a C Wire - What Do I Do?

June 09, 2021

When you’re looking for approaches to lower heating and cooling bills, getting a smart thermostat is an intelligent move. These devices adjust to the temperatures you like and routine and then develop an energy-efficient schedule that matches. What’s even better is that you can change and watch your settings from almost anywhere with your phone, whether you’re sitting in bed or on the go. (You might even be able to receive a free smart thermostat depending on rebate programs from your utility company in Elk River.)

Most of the time, installing a smart home thermostat with the help of Home Comfort Heating & Air is a straightforward process if you have a new home. But what if your residence is older or doesn’t have the right wiring? Can you still install a smart thermostat without C wire? We’ll help you figure out the process so you can pick the ideal thermostat and get energy savings for many years.

What Is a C Wire and What Does It Do on a Thermostat?

Many programmable thermostats run on batteries. When you’re making the move to a smart thermostat, you’ll discover that many need a C wire, or common wire, for power. If you don’t have this wire, your new thermostat could cause your heating and cooling system to malfunction.

You can find out if you have a C wire by doing the following:

  1. Cut power to the thermostat at the breaker.
  2. Pull off the thermostat and look at the wiring.
  3. If there are five or six multicolored wires, you have what’s required for a smart thermostat. You might be thinking what color is the C wire on a thermostat—and the answer to that is typically blue.
  4. If there are three or four thin multicolored wires, you’re close. Check the C wire isn’t hidden within the wall. If you can’t find one, we may be able to add one for you or you may be able to operate your new thermostat without one.
  5. If you have two thick wires, you may be able to run a smart thermostat with an adaptor just for high-voltage systems. Or you may be able to operate a battery-powered smart thermostat, like the Lux Geo Wi-Fi Thermostat, if your wiring won’t work and you don’t want to replace it.

Do Nest or ecobee Need a C Wire?

Two of the top brands are the Nest smart thermostat and ecobee smart thermostat. If you have two to four wires, these thermostats could be an option for you.

Nest says its thermostats are designed to run on minimal power and can typically share it with your HVAC system. However, you may need to have a professional like Home Comfort Heating & Air add a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re running into power problems or a battery that’s frequently drained.

ecobee connects with 24-volt systems (ones with three to six thermostat wires) and includes a C wire adaptor. So, you’re covered if you don’t have a thermostat C wire.

Trust Home Comfort Heating & Air for Your Smart Thermostat Installation Needs

At Home Comfort Heating & Air, we’re always looking for approaches to keep you more comfortable while keeping heating and cooling costs reasonable. If you want to know more about upgrading to a smart thermostat without a C wire, reach us at 763-276-0617. We can help you choose the right model for your house and even put in new wiring if necessary.