Sorry for the late chime in - I'm (theoretically) on vacation and don't have NFPA 20 with me.
As already stated, the 20 yields to other standards that may incorporate a fire pump into an approved water supply - 13, 14, 24, etc. Where 20 ends isn't defined, but the discharge control valve is as good a place as any. 14 allows segregating a building into zones using pressure reducing valves, but as Roland said there is a complex redundancy and potentially higher and lower flow rates that must be addressed and such zones could be comprised of 4 reducing valves. But 20 speaks to correct sizing, albeit in the annex. I want to say it's A.4.7.4, but as I said I don't have the book with so it may be a different section. In any case, it recommends that a pump be sized so that demand falls between 90-140% of rating. To arbitrarily oversize a pump (as specifying engineers are sometimes wont to do) and then slap a reducing (or worse, relief) valve into the discharge main is a bad practice. So if you have a pump that's oversized for the application, that arguably should be addressed in a more meaningful remedial way. You say that an insurance rep wants to limit pressure to an "older" part of the facility - why? What's the pressure? What's the underlying intent and is the pump correctly sized for the greater demand(s) of the newer part of the protected premises? Under selected circumstances, a listed reducing valve is a good solution, so long as it's installed per listing, applicable standard (13 and/or 14) and ... this is the tricky part ... REGULARLY INSPECTED AND TESTED PER 25. Steve L. Inafoodcoma New Orleans, LA -----Original Message----- From: [email protected] on behalf of Joe Powell Sent: Mon 6/3/2013 10:00 AM To: [email protected] Subject: Fire Pump - Pressue Relief Valve Does the 2010 NFPA 20 allow PRV's to be used to limit pressure on a fire pump system? The insurance inspector wants the existing pressure reducing valve to be replaced with a pressure relief valve. The pressure reducing valve is downstream of the fire pump and limits pressure on a supply to an older part of the facility. Joe C. Powell Pruett Ford & Associates, Inc. Consulting Engineers 1201 Broad Street, Suite 3A Augusta, GA 30901 Ph: 706-722-3959 Fax: 706-724-5127 Email: [email protected] _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
