Ground Rod Resistance Measurement

Used for measuring resistance to earth of an installed grounding electrode.

Ground rod resistance measurement.

The ability to properly measure ground resistance is essential in preventing costly downtime due to service interruptions caused by poor grounds. Since electricity seeks to move along the path of least resistance to the ground measuring the ohms of your grounding system will give you a sense of its overall safety. The three point method is the most thorough and reliable test method. Most of these agencies recommend a ground rod resistance reading or less than 5ohms when using a clamp on meter.

If there were 60 similar ground electrodes with a resistance of 10 ω each the measurement of the total loop resistance would be. A current is applied across the outermost pair of stakes and the voltage drop across the inner pair is measured with a ground resistance meter. Method 1 using a clamp on ground meter. Video of the day volume 0.

An ideal ground rod resistance should be below 3 ohms. Resistance 2 rods 2 5 ohms 2 rods 1 16 1 45 ohms resistance 3 rods 2 5 ohms 3 rods 1 29 1 075 ohms resistance 4 rods 2 5 ohms 4 rods 1 36 0 85 ohms. Make sure that your clamp on tester s jaws are fully closed as a semi opened clamp will significantly alter the measurement of the ground rod s resistance. For example the national electric code requires no greater than 25 ohms of resistance in a ground system.

Before measurements of ground resistance are conducted with a ground rod soil or ground resistivity testing is usually conducted with a series of four evenly spaced stakes. Rloop 10 ω 0 17 ω 10 17 ω. In facilities with sensitive equipment it should be 5ohms or less. 250 54 which requires the resistance to ground of a single made electrode e g ground rod to be 25 ohms or less.

Thus if your first ground rod measures 2 5 ohms we would expect the resistance of multiple rods to be the following. The resistance to the flow of electricity is measured by a ground meter and is read in ohms. That is why you have to fully familiarize yourself with your clamp on tester before you use it to measure resistances. The lower the number of ohms of resistance a grounding system has the better your protection is.