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

June 09, 2021

When you’re wanting methods to lower heating and cooling expenses, getting a smart thermostat is a smart idea. These devices learn your favorite temperatures and routine and then develop an energy-efficient schedule to match. What’s even better is that you can adjust and keep an eye on your settings from nearly anywhere with your phone, whether you’re sitting in bed or out and about. (You might even be able to receive a free smart thermostat depending on rebate programs from your utility company in Rapid City.)

In most instances, adding a smart home thermostat with the assistance of Precision Mechanical is a straightforward job if you have a newer residence. But what if your home is older or doesn’t have the right wiring? Can you still have a smart thermostat without C wire? We’ll help you demystify the process so you can pick the correct thermostat and receive energy savings for many years.

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

Most programmable thermostats need batteries. When you’re upgrading to a smart thermostat, you’ll learn that many require a C wire, or common wire, for power. Without this wire, your new thermostat could cause your heating and cooling system to malfunction.

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

  1. Switch off power to the thermostat at the breaker.
  2. Remove the thermostat and look at the wiring.
  3. If there are five or six multicolored wires, you have what’s needed for a smart thermostat. You might be pondering what color is the C wire on a thermostat—and the answer to that is usually blue.
  4. If there are three or four thin multicolored wires, you’re nearly there. Make sure the C wire isn’t tucked within the wall. If you can’t find one, we may be able to put in 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 install a smart thermostat with an adaptor specifically for high-voltage systems. Or you may be able to use a battery-powered smart thermostat, like the Lux Geo Wi-Fi Thermostat, if your wiring isn’t right 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 be a match for your home.

Nest says its thermostats are designed to run on very little power and can often share it with your HVAC system. However, you may need to have a pro like Precision Mechanical add a C wire with the Nest Thermostat E or Nest Learning Thermostat if you’re having power problems or a battery that’s constantly drained.

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

Trust Precision Mechanical for Your Smart Thermostat Installation Needs

At Precision Mechanical, we’re always seeking ways 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, contact us at 605-206-3766. We can help you choose the right model for your residence and even install new wiring if required.