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 <micah...@gmail.com> Sent: Tuesday, October 31, 2023 6:53 AM To: SprinklerForum <sprinklerforum@lists.firesprinkler.org> 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 sprinklerforum-le...@lists.firesprinkler.org
