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

June 09, 2021

When you’re seeking methods to lower heating and cooling expenses, getting a smart thermostat is a smart move. These devices pick up on the temperatures you like and routine and then create an energy-efficient schedule that fits. What’s even better is that you can change and keep an eye on your settings from nearly anywhere with your phone, whether you’re lying in bed or away from home. (You might even be able to get a free smart thermostat depending on rebate programs from your utility provider in Portland.)

Most of the time, hooking up a smart home thermostat with the support of Three Rivers Heating & Cooling is a straightforward task if you have a more modern house. But what if your residence is older or doesn’t have the correct wiring? Can you still add a smart thermostat without C wire? We’ll help you figure out the process so you can pick the correct thermostat and get energy savings for a long time.

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

The majority of programmable thermostats need batteries. When you’re making the move to a smart thermostat, you’ll learn that many have to have a C wire, or common wire, for power. If you don’t use this wire, your new thermostat might cause your heating and cooling system to have malfunctions.

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

  1. Cut power to the thermostat at the breaker.
  2. Take off the thermostat and check the wiring.
  3. If there are five or six multicolored wires, you have what you need for a smart thermostat. You might be wondering what color is the C wire on a thermostat—and the answer to that is often blue.
  4. If there are three or four thin multicolored wires, you’re close. Check the C wire isn’t rolled up inside the wall. If you can’t find one, we may be able to add one for you or you may be able to use your new thermostat without one.
  5. If you have two thick wires, you may be able to run a smart thermostat with an adaptor specifically 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 install new wiring.

Do Nest or ecobee Need a C Wire?

Two of the best-selling brands are the Nest smart thermostat and ecobee smart thermostat. If you have two to four wires, these thermostats could work for you.

Nest says its thermostats are designed to run on not a lot of power and can frequently share it with your home comfort system. However, you may need to have a professional like Three Rivers Heating & Cooling install a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re running into power problems or a battery that’s always drained.

ecobee works with 24-volt systems (ones with three to six thermostat wires) and comes with a C wire adaptor. So, you’re taken care of if you don’t have a thermostat C wire.

Rely on Three Rivers Heating & Cooling for Your Smart Thermostat Installation Needs

At Three Rivers Heating & Cooling, we’re always looking for ways to keep you cozier while keeping utility expenses reasonable. If you have questions about switching to a smart thermostat without a C wire, reach us at 503-213-4433. We can help you choose the right model for your house and even add new wiring if required.