How to Ground a Thermostat


You may need to attach a ground wire when you install a thermostat to control the heating or cooling of your home. Many newer 24-volt thermostats do not require a separate ground wire because they are grounded through the furnace or air unit that powers them. Also, many two-wire thermostats act as simple switches and do not have a ground wire. Thermostats that require a groud wire typically will have a short wire (usually green) coming off the case or a screw on the case marked as the ground connection.

Things You'll Need

  • Screwdriver
  • Wire nut


  • Turn off power to the thermostat either at the breaker or at the device (AC or furnace) that supplies power to the thermostat.

  • Unmount the thermostat.

  • Locate the thermostat's ground wire (usually green) or ground screw. Refer to the instructions that came with the thermostat to find out where the ground connection is on your model.

  • Locate the ground wire at the installation site. If you are not sure which wire is the ground, don't guess -- a wrong connection could lead to injury or damage to equipment. Sometimes you can locate the ground wire at the installion site because it ends at a connection to a metal part such as a junction box (a small metal box in your wall that supports the thermostat and encloses the electrical wire ends.)

  • Twist the ends of the two ground wires together and screw a wire nut onto the wire ends. If your thermostat has a grounding screw instead of a wire, loosen the screw, wrap the ground wire around it, and tighten it with a screwdriver.

  • Remount thermostat.

  • Turn the power back on and check thermostat to make sure it works properly.

Tips & Warnings

  • If you are sure your thermostat requires a ground wire but you cannot locate one at the installation site, you may need the help of an electrician.

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  • Photo Credit wire-nut image by Jim Mills from
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