Greg, You are absolutely correct. The fire department is the end user of the hose valve so they should have final say in the outlet pressure requirements. If they are concerned about pressures over 100-psi for safety reasons, then follow their guidelines for selecting the PRV’s.
Jordan, Follow Greg’s procedure of adjusting the PRV to the local AHJ’s guidelines. Rick Matsuda > On Oct 31, 2023, at 11:17 AM, Greg McGahan <[email protected]> > wrote: > > > With all due respect Rick, I have had Fire Departments very concerned about > the residual pressure being greater than 100 psi for safety. > > Sizing PRV's is not the easiest part of a standpipe design. If you are in a > jurisdiction that requires flow testing and recording the pressures prior to > the final inspection (as it should be per NFPA 14), guessing could cost a lot > of money to correct. > >> On Tue, Oct 31, 2023 at 10:49 AM Rick Matsuda <[email protected]> wrote: >> The requirements of NFPA-14 for the standpipe hose valves are maximum >> 175-psi static outlet pressure and minimum 100-psi residual outlet pressure >> while flowing 250-gpm through the hose valve. >> If your pump source is from the city mains, then make it easy on yourself >> and select a PRV hose valve that will provide maximum 165-psi static outlet >> pressure. >> This should allow you to use whatever residual inlet pressure while flowing >> the 750-gpm total standpipe demand and still provide the minimum 100-psi >> residual outlet pressure. >> >> I used the 165-psi static outlet pressure cause the pump inlet pressure may >> vary up/down which will vary the pump static outlet pressure which may raise >> the static outlet pressure over 175-psi. >> >> If the pump source has a constant pressure like an elevated tank, then >> select a PRV that will provide a maximum 175-psi outlet pressure. >> >> Just my opinion but if you select a PRV based on the maximum static outlet >> pressure then this should allow a bit more than the 100-psi minimum outlet >> pressure. Check the charts to verify this. >> Don’t select a PRV based on providing just the minimum outlet pressure. >> I think that the fire department will appreciate any extra pressure to >> offset the friction loss through their fire hoses. >> Rick Matsuda >> >>>> On Oct 31, 2023, at 7:24 AM, Eric Rieve <[email protected]> wrote: >>>> >>> >>> Micah, >>> >>> >>> >>> Looking at the spec sheet from Zurn I agree with Travis that you use your >>> expected residual pressure while flowing the full system demand of 750gpm. >>> I haven’t installed this valve myself, but you’ll notice on the residual >>> pressure charts that the bonnet type curve lines stop well below 175psi. >>> So, while you may pick a 120psi outlet pressure while flowing 750gpm, the >>> extra play in the curve should allow the valve to maintain an outlet >>> pressure below 175psi when being tested individually at 250gpm. >>> >>> >>> >>> Hope this helps! >>> >>> Eric Rieve, SET >>> >>> Rieve Fire Protection >>> >>> >>> >>> From: Micah Davis <[email protected]> >>> Sent: Tuesday, October 31, 2023 6:53 AM >>> To: SprinklerForum <[email protected]> >>> Subject: [Sprinklerforum] Pressure Regulating Valves Residual Pressures >>> >>> >>> >>> Good morning, Forum! I hope everyone is having a great week!! >>> >>> >>> >>> I think I got this right, but someone is questioning me. I have an >>> automatic standpipe with factory pressure-regulating valves (i.e., Zurn >>> 4000). When calculating residual pressures at the inlet of the PRV to be >>> used in the sizing charts, the question is, how much water should I be >>> flowing in the system? One suggestion is only flowing 250 gpm at the hose >>> valve you are sizing. The other suggestion is flowing the system demand >>> flow per NFPA 14. In this case, that would be 750 gpm (250 gpm at each of >>> the two most remote hose valves plus 250 gpm at the top of the only other >>> standpipe). We are in agreement that the calculation should be a source >>> calc to determine the actual pressure provided by the system. >>> >>> >>> >>> Thank you, >>> >>> Micah Davis >>> >>> Ferguson Fire Design >>> >>> >>> _________________________________________________________ >>> SprinklerForum mailing list: >>> https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org >>> To unsubscribe send an email to [email protected] >> >> _________________________________________________________ >> SprinklerForum mailing list: >> https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org >> To unsubscribe send an email to [email protected] > > > -- > Greg McGahan > > Genesis Fire Services, LLC > > 4912 Glover Lane. Milton, FL 32570 > > P- 850-637-8535 > > C- 850-712-9555 > > > _________________________________________________________ > SprinklerForum mailing list: > https://lists.firesprinkler.org/list/sprinklerforum.lists.firesprinkler.org > To unsubscribe send an email to [email protected]
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