Underground Fire Sprinkler Pipe Grounding and Bonding - Electrical System vs Lightning Protection

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Question​

Can the underground fire sprinkler piping be used to bond to lightning protection, but not as a grounding electrode for the electrical system per NFPA 13?

Answer​

Yes, that is correct. According to NFPA 13, the underground fire sprinkler piping can be bonded to the lightning protection system, but it cannot be used as a grounding electrode for electrical systems.

Explanation​

NFPA 13 - Section 6.5 Grounding and Bonding​

6.5.1Underground fire protection piping shall not be used as a grounding electrode for electrical systems.
This prohibition is in place to prevent the potential risks associated with using underground piping for electrical grounding. Specifically, grounding electrical systems to underground fire protection piping can lead to stray ground currents and increased galvanic corrosion. Additionally, if the piping system includes nonconductive materials like PVC, it may not provide a reliable ground, further increasing the risk.

6.5.1.1Bonding of the underground piping to the lightning protection grounding system is allowed where lightning protection is installed as per NFPA 780.
In scenarios where a structure has a lightning protection system, NFPA 13 permits the underground fire sprinkler piping to be bonded to the lightning protection grounding system. This ensures the entire system is effectively grounded for lightning protection purposes, as outlined in NFPA 780.

In Conclusion​

NFPA 13 explicitly forbids using underground fire sprinkler piping as a grounding electrode for electrical systems due to the risks of stray currents and corrosion. However, it allows bonding this piping to the lightning protection grounding system when required by NFPA 780, ensuring proper grounding for lightning protection without compromising electrical system safety. Electrical equipment grounding should always comply with NFPA 70, the National Electrical Code.