How to Test a Ground Rod

Co-authored by wikiHow Staff | Updated: March 29, 2019

A ground rod is an important part of an electrical system. It allows uncontrolled electricity to go to the ground instead of causing a fire or damaging a building. When installing a ground rod, you need to make sure that electricity will easily flow through it into the earth. The resistance to the flow of electricity is measured by a ground meter and is read in ohms. The lower the number of ohms of resistance a grounding system has, the better your protection is.

Method 1 | Using a Clamp-on Ground Meter

1 | Get a clamp-on ground meter

A clamp-on ground meter is a specialized electronic machine that checks electrical resistance. These meters can range from about $100 (USD) to over $1500 for professional models. They are available at hardware stores, home improvement stores, and online retailers of electrical supplies.

  • The clamp-on meter will give you a reading in “ohms,” which is the unit of measurement for resistance. It may be signified with the symbol “Ω” on the meter.

2 | Clamp the meter on the ground rod or grounding electrode conductor

Open the clamp by pressing the lever on the side of the meter and holding it down. Then put the clamp around the grounding electrode conductor or the top of the ground rod. Let the clamp close by letting go of the lever.

  • The meter should be used as close to the ground rod as possible. Using it further down the electrical system, such as near the electrical panel, will read other ground sources in addition to the ground rod.

3 | Turn on the meter

How you start the meter depends on the specific brand you have. Some simply have a button that says “power” or “on.” Others have a dial that needs to be set to ohms.

  • If you are unsure of how to turn on your ground meter, follow the directions included with it.

4 | Assess the readings on the meter

Method 2 | Using an Earth Electrode Tester

1 | Get an earth electrode tester

This is an older type of resistance meter that uses multiple ground probes and wires to assess a ground rod’s resistance. This type of tester is usually available at hardware and home improvement stores, as well as from online retailers.

  • Using an earth electrode tester instead of a clamp-on tester will take a lot more time and effort. If you have the option of using a clamp-on meter instead, do it.

2 | Insert 2 ground probes into the ground

The ground probes need to be inserted into the ground at specific distances away from the ground rod. The furthest ground probe needs to be at a distance that is 10 times the length of the ground rod. For instance, if the ground rod is 8 feet (2.4 m) long, the furthest probe should be 80 feet (24 m) away. The second ground rod should be located halfway between the furthest probe and the ground rod.

  • The ground probes are typically about 1 foot (0.30 m) long. They should be inserted into the ground until the top of them is just visible.
  • The leads that come with earth electrode testers are typically very long, so they should reach the required distance.

3 | Connect all three leads

The three leads your meter comes with should be inserted into the openings on the meter. Then, the other end of 1 of the leads needs to be connected to the top of the ground rod. The other 2 each need to be connected to one of the ground probes.

  • In general, it doesn’t matter which lead goes to which ground rod or probe. However, the lead for the furthest ground probe should be the longest one so that it will reach.

4 | Turn on the meter and take a reading

How you turn on the meter depends on the specific type of meter you have. Most have a dial that should be set to the ohm symbol or to a mark that says “3 pole,” which is referencing your 3 points of contact with the earth. Once the meter is on, read what the screen says.

  • If a ground rod has a good connection to ground, its reading should be a number below 25.

5 | Verify your original reading

Move one of your probes to a location 2 feet (0.61 m) closer to the ground rod. Take a reading of the resistance once again. Then move that same probe so it is 2 feet (0.61 m) closer to the second probe than it was originally. Take another reading. All the readings that you get should be very similar.

  • To ensure that your ground rod is sufficient, the average of all 3 readings should be less than 25 ohms.

Method 3 | Reducing Grounding System Resistance

1 | Make sure the grounding system connections are secure

If you don’t get a satisfactory ground reading, check your grounding system for problems. Make sure the clamp that connects the ground rod and the grounding circuit conductor is very tight. Also ensure that the ground electrode conductor is solidly connected to the grounding bar in the electrical panel.

  • Most electrical systems also have secondary grounding means, such as the grounding bar being connected to a cold water pipe that goes into the ground. Make sure that the secondary grounding means is also securely connected.

2 | Install a new ground rod in a different location

In some instances, ground rods can be installed in areas where the earth has a lot of resistance. For instance, if a ground rod is driven into a very rocky and dry area it may not conduct electricity into the ground well. If this is the case for your ground rod, the best solution is to drive a different rod into a different location.

  • This may not require you to put a ground rod a long distance away from the original rod. Even a few feet can make a difference for the ground resistance.

3 | Install a second ground rod

If you have too much resistance in your initial ground rod, you can connect a second one in series to reduce the overall resistance. This will ensure that any ground fault will be able to go to ground easily.

  • Your second ground rod should be located at a distance that is equal to the length of your ground rod. For example, if your first ground rod is 8 feet (2.4 m) long, your second ground rod should be located 8 feet (2.4 m) from the first ground rod.

How to Install Ground Rods

Co-authored by WikiHow Staff | Updated: July 14, 2019

Ground rods are an important part of having a safe electrical system. They create a route for stray electricity, which occurs during a short or other malfunction, to have a efficient route out of a building. To begin installation, you need to find an appropriate location to install them and then drive them into the ground. Once the rods are in the ground, then you need to ensure that they are connected to the electrical system they are grounding correctly. With a bit of planning and care, you can install grounding rods for a new electrical panel or for an existing panel in order to minimize the threat of electrical fire and injury.

Part 1: Picking the Location

1 | Install the rod in a location near the electrical panel

Ground rods need to be installed in the ground outside in a spot where they can be hammered 8 feet (2.4 m) into the ground. There is no requirement for how close or far from a building they should go, but be sure to pick a spot that is convenient to get to and where you will have space to use tools to drive the rod into the ground.

  • If a grounding rod is too close to a building foundation, it could interfere with it. Because of this, it’s best to keep it at least 2 feet (0.61 m) from the side of the building.

2 | Plan the route for the grounding electrode conductor

Once a ground rod is driven into the ground, it will need to be connected to the electrical panel inside. This is done with a wire called the grounding electrode conductor. It’s important to factor its route in when picking a spot for the ground rod. Make sure the grounding cable can easily be routed to the panel from where the grounding rod is positioned.

  • If you have an idea of where you would like to drill a hole in your building to get the conductor inside, pick a spot for the grounding rod nearby.

3 | Avoid locations where the ground is mostly rock or heavily compacted

Because you have to drive the rod 8 feet (2.4 m) into the ground, you want to avoid areas that are excessively rocky. While you wont always be able to avoid rocks or know they are there, avoid picking an area that you know is full of rocks.

4 | Locate any wires or pipes in the path of the ground rod

Once you have picked a spot to put your ground rod, you need to make sure you will not damage anything in the ground when you install it. In many countries, there are hotlines you can call to have your utilities located free of charge. In the US, for example, there is a national hotline that you can call in order to notify your utilities that you need a locator.

  • It usually takes about 2-3 days for the utilities to come and do the locating, so plan ahead.
  • If there is no locating hotline in your areas, you can call the utility companies directly that serve the building and ask them to locate their underground lines.

Part 2: Putting the Rod in the Ground

1 | Purchase an approved grounding rod

Grounding rods need to made of specific conductive metals and they need to made to a specific length and width. Because of this, it’s best to buy a rod that is specifically made for this use. Buying a listed rod, meaning it has been verified by a certification group, will ensure that your grounding rod is the correct size and material. Most home improvement and hardware stores stock approved grounding rods.

  • In the US, ground rods need to be at least 8 feet (2.4 m) long. If they are listed, they need to be at least 1⁄2 inch (1.3 cm) wide and they will have a mark that says they are listed. If they are not listed, they need to be at least 5⁄8 inch (1.6 cm) wide.
  • A listed ground rod will have a marking near the top of it that states that it is approved. The mark allows an electrical inspector to immediately know you have used a proper rod.

2 | Start digging a hole with a shovel or post-hole digger

Because a ground rod is so long, it can be hard to get leverage on the top of it when you start installing it. To get the top down to a more manageable level, dig a hole 2–4 feet (0.61–1.22 m) deep. By putting the end of the ground rod in the hole, it will be easier to start hammering the top of the rod.

  • If you don’t want to dig a hole or you can’t for some reason, you will need a ladder or step stool to get up high enough to start pounding in the top of the ground rod.

3 | Drive the rod into the ground

Using your hammer, drill, or driving tool, gradually drive the rod vertically into the ground. You need to drive your rod all the way into the ground. The electrical code states that it must have 8 feet (2.4 m) of contact with the ground, so you need to drive it all the way down.

  • Driving a ground rod into the ground can take a long time and can be difficult work. If you can find someone to take turns driving the rod, it will make for a much easier job.
  • Some electrical inspectors will allow you to leave 1–2 inches (2.5–5.1 cm) sticking up out of the ground. However, some want the entire thing covered in earth.

Part 3: Connecting the Rod

1 | Pull the grounding electrode conductor to the grounding rod

Once the grounding rod has been driven into the ground, you need to connect it to the electrical system of the building. Pull the grounding electrode conductor up to the top of the grounding rod, making sure it is long enough to make a permanent connection between them.

  • Give the grounding electrode a little bit of slack, so it’s not extremely tight where it connects with the grounding rod. This will ensure that if it gets hit or pushed on, it won’t get dislodged from the grounding rod.
  • If the grounding electrode conductor has a sheath on it, the last 1⁄2 inch (1.3 cm) should be cut off, exposing the wire.

2 | Clamp the grounding electrode conductor to the grounding rod

There are specific clamps that are used to connect grounding electrode conductors to grounding rods. You will need 1 clamp. Put the end of the conductor and the end of the rod inside of the clamp and turn the screw on the clamp to press them together securely.

  • These clamps are sold in home improvement and hardware stores.

3 | Connect the grounding electrode conductor to the ground bus

The ground bus is where all the ground and neutral wires are attached in the electrical panel. To make the connection, slide the end of the grounding electrode conductor through one of the holes in the bus and tighten the screw in that hole until it holds the wire very tightly.

  • In some cases, the ground wires will be connected to the ground bus and the neutral wires are connected to the neutral bus. These 2 bars are then connected with a main bonding jumper. If this is the case, you can attach your grounding electrode conductor wherever it fits on either bus.
  • You need to be very careful when you are doing any work in an electrical panel. Make sure that your fingers, tools, and the grounding electrode conductor don’t make contact with the energized bars in the panel, which are located behind the circuit breakers.
  • If you are unsure about how to make this connection safely, hire an electrician to do the work.