Thank you for your question regarding the grounding of swimming pools, it is our pleasure to help.
The National Electrical Code (NEC) can be a bit confusing when it comes to the grounding requirements of swimming pools. There are two (2) sections that you must pay attention to inside the NEC, specifically articles 250 and 680. First of all, it is important to understand the basic concept the NEC is trying to get across when it comes to swimming pools grounding, and that is “equipotential bonding”.
Equipotential bonding is comprised of three (3) basic components:
- Making a connection to the earth, properly known as earthing; however also known as grounding. This leads to much confusion because in America we use one word, “grounding” for both above-grade and below-grade grounds. Earthing refers to only the below-grade portion of grounding.
- The bonding of all metallic objects so they are at the same potential
- Providing a low-impedance path for fault currents. The intent of a “low impedance path” is to provide a direct copper path, not an indirect steel path with lots of mechanical joints. This is an additional ground path required especially for pools.
Equipotential Bonding is covered under NEC Article 680.26. We recommend the NEC Handbook as it contains a number of really excellent full-color illustrations that will answer most of your questions for you. Keep in mind that the low-impedance ground path mentioned in 680.26 is in ADDITION to the low-impedance path required for Over Current Protection Devices (OCPD) required under 250.4(A)(3). Also, you should pay special attention to the sizing of ground conductors when dealing with swimming pools, in particular NEC Articles 250.122 and 680.26(B).
You of course must also purchase junction boxes that are compliant with 250.8 and 680.24, provide ground fault circuit interrupters (GFCI), provide an equipotential bonding plane for all paved walking surfaces within 3-ft of the pool (NEC 680.26(C)), and bond underwater lights in accordance with NEC 680.23(F).
Ultimately, you are going to need to add a lot of additional copper conductors in order to bond the steel rebar in the swimming pool, the metal fences near the pool, the diving board, metal hand rails, pumps, heaters, lights and any other metallic object related to the pool or within range of the pool. And of course, the pool grounding must be bonded back to the buildings common grounding grid, which will include the utility grounding system, water pipe, building steel, gas pipe, Telco, lightning protection, etc.
If you are building a public swimming pool and are near any form of high-voltage source such as a delta transformer fed from the utility with an unknown OCPD, overhead power lines, or a nearby substation, you may be required under federal and/or local laws to conduct a human safety study to ensure that hazardous Step & Touch Voltages will not form that could injure the occupants of the pool.
We hope this has answered your questions, if you should need any assistance with your swimming pools safety design or have further questions, please do not hesitate to call us at 310-318-7151. We will be glad to speak with you about your project, free of charge.
The Engineering Team at E&S Grounding Solutions
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