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Discover How to Find a Ground Wire in 4 Different Ways

It can be alarming when you open up your outlet or fuse box and see a cluster of multi-colored wires criss-crossing in a maze of yellows, greens and reds. How do you know which wire is which, and more specifically, how do you identify the ground wire out of the rainbow of options? 

Fortunately, the National Fire Protection Association (NFPA) took it upon themselves to standardize electrical wiring so they’re easier to identify based on color, thickness and location. This is known as the National Electrical Code, or NEC. If you want to gain a basic understanding of electrical wiring and safety, learn how to find a ground wire in the guide below.

What Does a Ground Wire Do

A ground wire’s main purpose is to provide a safe path for electricity to travel in the case of internal short circuits or external exposures, such as lightning or static electricity. This protects against overloads, machine damage, fires and electrocutions.

To shore up any loose ends, ground wires are connected to any conductive surfaces electricity might flow through. You’d be in for quite the shock if you went to open your dishwasher and were met with 120 volts instead. That’s where the ground wire comes in. They prevent you from being electrocuted from touching any metal components, such as the exteriors on an appliance or the metal plates on a receptacle. 

House socket wiring diagram-How to find a ground wire 1

How to Find a Ground Wire 

Since ground wires, also known as earth wires, are an integral part of electrical safety, it’s important to ensure they are present and properly connected. However, the NEC is a guideline that is not enforced by the federal government. That means sometimes you can’t go off color alone. Luckily, though, ground wires have some tells that we’ll go over here.

  • Color – Ground wire colors are typically green, an alternating green-yellow sheath or are a bare, copper wire. You can also check the insulation for the “PG” label, which stands for protective ground. Any ground screws should also appear green.
  • Thickness – Ground wires are typically the same gauge as the lead wires because they need to be able to carry the same current load. For this reason, neutral and hot wires will always be the same size. However, this isn’t always the case for ground wires. They may be a different size for various reasons, so if you see a wire that’s not the same size as the others, this will most likely be your ground wire. 
    • Note: You should always assume a wire is hot and never touch it without verifying it is indeed the ground wire with a multimeter or other testing equipment.
  • Length – Ground wires should take the shortest, most direct route to the ground rod. This is because longer wires have a higher resistance, which, in certain circumstances, can impede the ground wire’s ability to trip a circuit breaker. 
  • Location –  In a properly wired household outlet, the ground wire will be connected to the U-shaped opening. You can also identify a ground wire if it's connected to external surfaces not a part of the circuit, like a pipe or the housing of an appliance. If you still couldn’t identify the ground wire based on these characteristics, we still have a few tricks up our sleeves. For one, you can try tracing the wire back to its source or, two, test the wires for voltage

There are two reasons you might pick up readings on all the wires. One, ground wires might detect a current if it’s currently intercepting it. Or, two, there simply might not be a ground wire in your receptacle. If either of these instances are true, it’s best to leave it up to the professionals and contact an authorized service technician.