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Test Ground Rod By Using An Earth Electrode Tester

Update:02 Jan 2019
Summary:

Ground rods are an important part of having a safe elec […]

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.

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.

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.

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.

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.

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.