Mike asks us: “Does my electrical earthing system need to be connected to my buildings fire sprinkler system?”
Thank you Mike for the great question. Yes, your building or structures fire sprinkler system must be bonded to the common earthing system in accordance with the National Electrical Code NEC 250.104, and 250.104(D)(1); the Lightning Protection Code NFPA 780 4.14; and the Fire Sprinkler Code NFPA 13 10.6.8.1. It is also required under NFPA 24 the code for the installation of private water service.
It is important to remember that there is a difference between bonding a metal object to ensure that there are no differences in potential, and in using that metal object as a fault current path and/or a earthing electrode. You may NOT use the fire sprinkler system as a fault current path or as a earthing electrode.
You should have an electrically isolating flange installed at the base of the fire rise, which will prevent your electrical system from using the buried fire rise supply pipe as an electrode. Of course, you may not use the fire sprinkler pipes as a earthing electrode conductor anywhere within the facility. However, each and every riser should have a copper or aluminum conductor bonding the riser back to the main earthing system in a manner that does not place it in series with any other electrical system. A single tap from a earth bar is the best method.
As you can see in this photo, the fire riser has two pipe clamps connected to a earthing conductor that is routed back to the main earthing system and bonded to a earth bar.
Please feel free to contact us at 310-318-7151 during California working hours, and someone will be glad to speak with you about your questions.
The Engineering Team at E&S Earthing Solutions
The United States Fire Administration