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For a home electrical wiring, is it acceptable to have to multiple earth rods on different (reasonably apart from each other) locations?

In good practice, to keep earth resistance low, we use multiple earth rods with a distance to maximize efficiency and connect them together. But I'm asking if we keep two earth rods across the installation area and if they connected to the circuit from (diferent) two points is there any risk?

Is there a possibility on lightning or other high voltage surge, two distance earth rods cause potential difference across them and damage?

This question is not about ELCB or RCCB devices. This is explicitly about having multiple earthings with reasonable distance and HV surges like lightning strikes

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  • \$\begingroup\$ Acceptable according to building laws? Or acceptable according to physics? \$\endgroup\$ Commented Apr 21, 2022 at 15:45
  • \$\begingroup\$ Multiples earth rods are ok. But only one ground point. \$\endgroup\$
    – Antonio51
    Commented Apr 21, 2022 at 15:45
  • \$\begingroup\$ It depends on your local building codes and laws how the electrical installation should be made. Ask your local electrician. \$\endgroup\$
    – Justme
    Commented Apr 21, 2022 at 16:16
  • \$\begingroup\$ This is a purely scientific point of view question. I agree that we must follow regulations, but in my area there are things that not defined well, fyi \$\endgroup\$
    – Salitha
    Commented Apr 21, 2022 at 17:08

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Lightning will cause a potential gradient in the earth that can cause high voltage differences over even a short distance, this is called "step voltage" and is what can kill you in a nearby strike, your feet are far enough apart that there can be hundreds or even thousands of volts difference between them. You need to take this into account when designing a ground system.

Two ground rods spaced apart can have a very high difference in potential, if they are connected to equipment through different paths that voltage will cause high current to pass through the equipment. You would need to have the equipment connected to the grounding system by only one path. Then you need to worry about touch voltage, which will be the potential difference between the equipment and the floor/ground or anything else close enough that a person could touch both at the same time.

You can get an idea of the voltages involved from this document.

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You may have multiple grounding rods if they are bonded together. Do not bond equipment that is attached to the grid to a separated grounding rod. During a lightning strike, the potential at various points in the physical ground may be tens of thousands of volts different. Grounding rods that are not bonded together invite indirect lightning current to go up one grounding rod, through equipment and building wiring, and then down through a separate grounding rod. Bonding the grounding rods together will hopefully provide a lower impedance path between rods than your equipment provides.

You should not bond separate ground rods to neutral in separate places. Ground and Neutral should ONLY be bonded at the main breaker panel. Do NOT bond ground and Neutral at any sub panels, or at other points such as outlets.

Depending upon your jurisdiction, the rules just mentioned may be mandated by code. However, some jurisdictions do not have such rules. I would follow them anyway.

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