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NFPA 12 Grounding Requirement

Question asked by eptownie1988 on Nov 29, 2016

NFPA 12 2015 edition - Standard on Carbon Dioxide Extinguishing Systems

4.2.1* Carbon Dioxide fire-extinguishing systems protecting areas where explosive atmospheres could exist shall utilize metal nozzles, and the entire system shall be grounded.


Annex A

4.2.1 The discharge of liquid carbon dioxide is known to produce electrostatic charges that, under certain conditions, could create a spark. see (NFPA 77)


NFPA 77  2014 edition - Recommended Practice For Static Electricity Where wire conductors are used, the minimum size of the bonding or grounding wire is dictated by mechanical strength, not by its current-carrying capacity. Stranded or braided wires should be used for bonding wires that will be connected and disconnected frequently. (see Annex G for additional information)


So my question is how do you determine the proper wire size based on mechanical strength and why is the method of mechanical strength used over current-carrying capacity?