How to check ground rod resistance

Written by finn mccuhil
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How to check ground rod resistance
An effective grounding rod is important for electrical safety. (Jupiterimages/liquidlibrary/Getty Images)

A ground rod provides a safe path for electricity to follow in the event of a short circuit. To this end, electrical code requires that all electrical installations have a grounding rod installed. A grounding rod is a metal rod that is driven into the earth and attached to the electrical service panel with a conductive wire. Exposure to the elements, soil acidity and extreme temperatures can corrode this rod over time increasing its resistance thereby reducing its ability to conduct electricity. Checking a ground rod's resistance will increase the margin of safety for a home's electrical supply.

Skill level:
Moderate

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Things you need

  • 2 Auxiliary ground rods
  • Ground Resistance Tester

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Instructions

  1. 1

    Disconnect the ground rod to be tested from the electrical service. Loosen the wire-locking collar on the rod with a wrench and remove the ground lead.

  2. 2

    Insert the first auxiliary ground rod into the earth 33 feet from the ground rod to be tested.

  3. 3

    Insert the second auxiliary ground rod into the earth in a straight line from the existing ground rod and the first auxiliary, 33 feet from the first auxiliary. All three rods will form a straight line with the rods equally spaced over a distance of 66 feet.

  4. 4

    Connect the leads from the meter to the ground rods. Follow the manufacturer's instructions for your make and model of tester for correct lead placement.

  5. 5

    Press the "On" or "Test" button. The value shown on the meter's readout will be the resistance of the ground rod.

Tips and warnings

  • Read the documentation for your individual meter carefully for lead placement and exact test procedures.
  • Exercise extreme caution while working with electricity. Read and follow all safety procedures associated with your testing device and methods.

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