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Do I need down conductors to be bonded to the re-bar in concrete column?

Tominaga from Japan responded to an earlier comment and asked the following question:

Thank you very much for your recommendation & expertise.  I checked ANSI-TIA-EIA-J-STD-607-A and it says “This standard does not require bonding of the steel bars of a reinforced concrete building.” But for structural steel, metal frame, the telecommunication grounding shall be bonded to them.

Go back to the lightning protection down conductor, NFPA780 says “down conductors coursed on or in reinforced concrete columns or on structural steel column shall be connected to the reinforcing steel or the structural steel member at their upper and lower extremities.” If I follow your recommendation, then do I need down conductors to be bonded to the re-bar in concrete column?

Hi Tominaga,

You are correct in regards to the 607-A standard.  However, E&S Grounding Solutions always recommends that the steel columns and the rebar in the foundations be bonded together in ALL cases, regardless of lighting protection issues.  In fact, the NFPA 70: National Electrical Code mandates this practice.  The best source of information is in the NFPA 70: National Electrical Code Handbook.  Article 250 has numerous illustrations showing this mandatory bonding; Exhibit 250.22, Exhibit 250.23, Exhibit 250.29, Exhibit 250.31, to be specific.

In regards to your question “do I need down conductors to be bonded to the re-bar in concrete column?”, the answer depends a lot on how your building is constructed and arc-flash calculations.  But for a typical building, the lightning down conductors are generally only bonded to clearly exposed metal pieces that are immediately adjacent to the down conductors.  You would need to get an analysis completed to determine the arc-flash differences between the down conductors of the Lightning Protection System, and the steel columns.

To summarize, you should have copper down conductors for your lighting protection system, and you should have the steel columns bonded to the rebar in the concrete.

If you should have any questions or concerns, please feel free to call during regular business hours California time, and one of our engineers will be glad to speak with you about your project, free of charge.

Best regards,

The Engineering Team at E&S Grounding Solutions


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