Equipotential planes in livestock buildings
Where livestock can reach metal equipment that could become energized, the concrete floors and slabs they stand on need an equipotential plane bonded to the grounding system with 8 AWG or larger solid copper. In 2023 this rule moved from 547.10 to 547.44.
What the code requires
Agricultural buildings need an equipotential plane, a bonded conductive grid such as wire mesh in the concrete, where livestock can reach metal equipment that may become energized. For this rule, livestock does not include poultry.
Indoors, a plane is required in confinement areas with concrete floors. Outdoors, it is required in concrete slabs where such equipment is accessible, and it must cover the area where the animals stand while using the equipment.
The plane must be bonded to the grounding electrode system, or to an equipment grounding terminal in any panelboard of that grounding system, with solid copper not smaller than 8 AWG, insulated, covered or bare. Connections to the mesh use brass, copper or copper-alloy pressure connectors or clamps, or another approved means.
On the job
- The bonding has to be in place before the concrete is poured. In Minnesota, inspectors check it before the pour, so ask your inspector when they want to see it.
- Concrete pads at livestock waterers are a common place this rule applies.
- Older references cite 547.10. Under the 2023 NEC, the rule is 547.44.
Exceptions that matter
- Slatted floors supported by structures that are part of an equipotential plane do not need separate bonding.
What changed in 2023
In 2023 the rule moved from 547.10 to 547.44, and the required bonding connection point was clarified.
Related sections
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CSLB #354550 · C-10 Electrical · Licensed since 1978 · $25,000 contractor's bond