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

June 09, 2021

When you’re wanting ways to reduce energy bills, getting a smart thermostat is a wise decision. These devices adjust to your favorite temperatures and routine and then develop 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 on the go. (You might even be able to get a free smart thermostat depending on rebate programs from your utility supplier in Hodgenville.)

In most instances, installing a smart home thermostat with the help of Phelps Heating & Cooling is a simple process 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 navigate the process so you can choose the ideal thermostat and enjoy energy savings for many years.

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

The majority of programmable thermostats use batteries. When you’re upgrading to a smart thermostat, you’ll find that many require 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 ascertain 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 look at the wiring.
  3. If there are five or six multicolored wires, you have what you need 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. Ensure the C wire isn’t tucked within the wall. If you can’t find one, we may be able to install one for you or you may be able to run 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 install a battery-powered smart thermostat, like the Lux Geo Wi-Fi Thermostat, if your wiring is incompatible and you don’t want to install new wiring.

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 consume not a lot of power and can often share it with your HVAC system. However, you may need to have a professional like Phelps 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 frequently drained.

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

Depend on Phelps Heating & Cooling for Your Smart Thermostat Installation Needs

At Phelps Heating & Cooling, we’re always on the lookout for methods to keep you more comfortable while keeping heating and cooling costs reasonable. If you have questions about switching to a smart thermostat without a C wire, reach us at 270-358-3167. We can help you select the right model for your residence and even install new wiring if needed.