Code Change Summary: New code definition of the term “equipotential plane”.

In the 2020 NEC^®, the term “equipotential plane” was added to Article 100. Previously, the term was defined and used in both Article 547 (Agricultural Buildings) and Article 682 (Natural and Artificially Made Bodies of Water) but each definition was different from the other and defined in a way to tailor it to the specific needs of each individual article.

Now, the term “equipotential plane” is defined generally in Article 100 and further clarification or requirements are provided in each article where the term is used.

An equipotential plane is also defined in Article 547 as an area where wire mesh or other conductive elements are embedded in or placed under concrete, bonded to all metal structures and fixed nonelectrical equipment that could become energized, and connected to the electrical grounding system to minimize voltage differences within the plane and between the planes, the grounded equipment, and the earth.

Equipotential planes are required by Article 547 in agricultural areas with concrete floors where livestock is kept. They are also required adjacent to outdoor service equipment that controls equipment related to natural and artificially made bodies of water covered in Article 682.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC^® edition of NFPA 70.