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
- 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.
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.
- Photo Credit wire-nut image by Jim Mills from Fotolia.com
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