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What is the best grounding method(s) for an electrical system located in a basement of a building in a flood zone?

Sharad tells us that:

I have a Hotel Project in which grounding has to be done.  The Hotel has up to 15 floors.  My concern is that the grounding system consisting of transformer and generator will be located in the basement.  This place is basically tropical region where it can rain anytime and flood.  What could be the bet possible grounding method we can use to avoid accidents?

Hi Sharad,

Thank you for your question regarding basement grounding in a tropical environment, it is our pleasure to help.

When you are in a high-water table area such as in the tropics, the primary concern is that water could enter the basement and flood the electrical system.  This means that your building foundation will be water-proofed and electrically isolated from the soil.  You may not use your building foundation as an electrode.  You will also not be able to penetrate the concrete below-grade level for fear of allowing water to enter the basement.  You will need to install an electrode system that is separate from the building structure.  Keep in mind that you must still bond your building steel to the grounding system, you just may not use is as an electrode.

If you are in a lightning prone area, you may want to consider surrounding the building with a continuous buried ground ring with interconnecting 10-ft grounding rods.  This ring or “counterpoise” will provide a very effective grounding system that is usable by both your buildings electrical system and your buildings lightning protection system.  This ground ring should consist of at a minimum 4/0 AWG bare stranded copper conductor, buried in direct contact with the earth to a depth of 1.5-ft to 3-ft with 10-ft ground rods at 20-ft intervals.

We hope this helps!  Feel free to call us at 310-318-7151 California time should you have any further questions.  Someone will be glad to speak with you free of charge.

Best regards,

The Engineering Team at E&S Grounding Solutions


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