Perfect John. I'm glad I didn't have time to look it up earlier. I'd have bungled an explanation whereas yours was simple and elegant.
On Tue, Oct 11, 2011 at 7:18 PM, John Drucker <[email protected]>wrote: > More Facts..................Oh Boy...... > > Grounding is covered in NEC Article 250 Part II,III and IV, Bonding is > covered in NEC Article 250 Part V. Fire Sprinkler piping is not listed in > Article 250 as a permissible grounding electrode but is required to be > bonded. > > 2008 NFPA-70 (NEC) > > Article 100 > > Bonded (Bonding). Connected to establish electrical continuity and > conductivity. > > Grounded (Grounding). Connected (connecting) to ground or to a conductive > body that extends the ground connection. > > 2008 NFPA-70 (NEC) > > 250.90 General. Bonding shall be provided where necessary to ensure > electrical continuity and the capacity to conduct safely any fault current > likely to be imposed. > > 250.104 Bonding of Piping Systems and Exposed Structural Steel. > > (B) Other Metal Piping. "Where installed in or attached to a building or > structure, a metal piping system(s), including gas piping, that 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 the one or more grounding electrodes used. The > bonding jumper(s) shall be sized in accordance with 250.122, using the > rating of the circuit that is likely to energize the piping system(s). The > equipment grounding conductor for the circuit that is likely to energize > the > piping shall be permitted to serve as the bonding means. The points of > attachment of the bonding jumper(s) shall be accessible." > > In a nutshell the idea is to provide a low impedance path back to the power > source in order that sufficient fault current will flow to open the > overcurrent device preventing metallic components from staying energized. > The key is low impedance (less resistance) path, bonding does that. > > So here we go.... > > 1) 277V lighting circuit makes contact with an unbonded sprinkler pipe. No > current flows on the sprinkler pipe because the circuit is incomplete back > to the electrical service. The pipe is now energized at 277V. Joe the > fitter > comes along makes contact with the pipe and an electrical conduit which is > bonded and completes the circuit. However the human body is a high > impendence path, appx 2,100 ohms @ 277 Volts, so I=E/R = 277V/2,100 > Ohms=.131 Amps or 131 Milliamps, double what is need for ventricular > fibrillation. Enough to disrupt the heart but insufficient to trip the 20 > Amp circuit breaker. The victim is electrocuted. Joe sure was a good > fitter. > > 2) 277V lighting circuit makes contact with a bonded sprinkler pipe. > Current > flows because the circuit is complete back to the electrical service via > the > bonding jumper. This is a low impendence path, appx. 2 ohms (1000 ft of #12 > Copper) @ 277 volts, so I=E/R = 277V/2 Ohms= 138.5.9 Amps. The 20 Amp > circuit breaker instantly opens and the pipe is deenergized. Hey what > happened to the lights, Jimmy go get a flashlight, better yet coffee. > > Sure hope that helps, > > John Drucker, CET > Fire Protection Subcode Official > Fire/Building/Electrical Inspector > Fire Marshals Office > Borough of Red Bank, NJ > > Not the official position of any agency, association, committee or > otherwise. Obtain required applications, permits, inspections and > approvals > from Authority(s) Having Jurisdiction. > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Steve > Leyton > Sent: Tuesday, October 11, 2011 5:59 PM > To: [email protected] > Subject: Grounding > > Assuming it's in there somewhere, where does 13 and or 24 speak to > attaching bonding or grounding wires to sprinkler systems? Question > posed to me today and I had to admit that I don't know ... hate it when > that happens. > > > > Steve Leyton > > PROTECTION DESIGN & CONSULTING > > 2851 Camino del Rio South, Suite 400 > > San Diego, CA 92108 > > ------------------------------------------------------------- > > Ph: 858.751.2930 - ext. 102 > > Fax: 858.751.2933 > > Cell: 619.972.5696 > > > > > > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > < > http://fireball.firesprinkler.org/mailman/private/sprinklerforum/attachment > s/20111011/20e3d0e9/attachment.html> > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > -- Ron Greenman Instructor Fire Protection Engineering Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: ASEE, SFPE, ASCET, NFPA, AFSA, NFSA, AFAA, NIBS, WSAFM, WFC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://fireball.firesprinkler.org/mailman/private/sprinklerforum/attachments/20111011/3f98e9bf/attachment.html> _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
