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

June 09, 2021

When you’re looking for methods to decrease energy expenses, upgrading to a smart thermostat is an intelligent move. These devices pick up on the temperatures you like and routine and then make an energy-efficient schedule that matches. What’s even better is that you can change and keep an eye on your settings from almost anywhere with your phone, whether you’re relaxing in bed or on the go. (You might even be eligible for a free smart thermostat depending on rebate programs from your utility supplier in Opelika.)

In most instances, adding a smart home thermostat with the support of Farnell Mechanical, Inc. is a straightforward process if you have a newer home. 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 choose the recommended thermostat and enjoy energy savings for years to come.

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

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

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

  1. Turn off power to the thermostat at the breaker.
  2. Pull off the thermostat and check the wiring.
  3. If there are five or six multicolored wires, you have what’s needed for a smart thermostat. You might be thinking 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 almost there. Check the C wire isn’t rolled up within the wall. If you can’t find one, we may be able to add 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 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 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 be a fit for your needs.

Nest says its thermostats are created to require very little power and can often share it with your HVAC system. However, you may need to have a professional like Farnell Mechanical, Inc. put in 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 connects 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 Farnell Mechanical, Inc. for Your Smart Thermostat Installation Needs

At Farnell Mechanical, Inc., we’re always seeking ways to keep you cozier while keeping utility costs low. If you want to learn more about switching to a smart thermostat without a C wire, reach us at 334-245-4748. We can help you pick the right model for your home and even add new wiring if necessary.