The change was made because reviewers were requiring many inlets when system demand was high (aka mains were being the 4”). The old text said FDC shall be a minimum 4” so some extrapolated that to if supply main was bigger so should the FDC. Supplement is technically incorrect since as you said 99.9% of the time only one or the other is feeding the system but it fixed the old misunderstanding.
Roland Huggins, PE - VP Engineering American Fire Sprinkler Assn. --- Fire Sprinklers Saves Lives Dallas, TX http://www.firesprinkler.org <http://www.firesprinkler.org/> > On Nov 25, 2014, at 6:12 AM, [email protected] wrote: > > noun: supplement; plural noun: supplements - something that completes or > enhances something else when added to it. > > How can the possibly pressure be supplemented? Using enough pressure to open > the FDC check valve will close the valve in the riser. The rule should be > changed to either calculated or just require a 4" 2-way FDC for everything. > > There are buildings in Phoenix with 12 - 2 1/2 " FDC inlets because of an > old amendment requiring one 2.5" inlet for every 250 gpm system demand. The > rule was changed when the FD figured out that a pumper truck only carried > enough equipment to connect to four inlets. > Ron F _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
