Grounding of metal buildings

What Is Electrical Grounding? Electrical grounding or “Grounding” originally began as a safety measure used to help prevent people from accidentally coming in contact with electrical hazards. Think of it as a master fail-safe for your electrical system.

PJ Inquired:I bought a 40X24 Metal frame with metal sidings building. No Elec or plumb at present, maybe later. Inspector requires grounding Metal Building. 1×5/8”x8’cu clad steel rod ok tied to frame? Any other options?

The Answer:First and foremost, you must follow the rules of your local inspector. He is the Authority Having Jurisdiction (AHJ) and has the final say. If you disagree with the inspector, you can appeal his decision, but in the end you must do what he says.

The National Electrical Code (NEC) is not a law, but is often cited by local laws as the standard to follow. In most cases, the local laws have additional requirements beyond those found in the NEC. It is important to know which version of the NEC your local jurisdiction follows. You can purchase your own copy of the NEC by visiting the National Fire Protection Association (NFPA) at http://www.nfpa.org/.

NEC Article 250.110 requires that all exposed normally non-current-carrying metal parts of fixed equipment, that are likely to become energized, shall be connected to the equipment grounding conductor. This means that if you have any metal object that could accidentally have electricity flowing through it, it must be grounded. This is a safety issue. If a “hot” wire were to accidentally touch the metal siding of your building, the entire building could become energized and anyone who touched it could be electrocuted. By grounding the building, you provide a safe path for the electricity to flow to the earth, which should trip a breaker and cut off the electricity.

Additionally, NEC Article 250.104(C) requires that exposed structural metal that forms a metal building frame, that is not intentionally grounded or bonded and is likely to become energized, shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to one or more grounding electrodes used. This means that you must have your metal building bonded to your grounding system.

In short, your inspector is correct in requiring you to ground your metal building. A 5/8” x 8 ft copper-clad steel ground rod is a very standard and acceptable electrode. You will need to install it correctly and bond it to your metal building with the proper sized conductor and use the correct listed hardware. We recommend a #6 AWG copper wire as a minimum, but you may need a larger conductor depending on the amperage of your electrical system. You should have a qualified electrician handle this for you.

Good luck!