The Zurn 5000 is fully field adjustable and can be easily relaxed or restricted while setting. Have you asked the local FD if they want to go conservative (i.e. use the theoretical residual pressure at full demand based on your calculations) as the inlet pressure or do they want to set the valve based on the actual flow during commissioning? If you use the theoretical, there will be less restriction and the final setting will allow a higher than 100 residual (if that's the benchmark) and if you set the valve while only flowing one outlet, higher demand conditions would be lower. The FD can adjust the valve during a fire fight, so it's all relative and they can also pump the system up to the limit of their capacity, there are contingencies built in. You could also commission each valve at 300 GPM to add a bit of safety factor to the more liberal approach. Check with the responding fire department to see if they have a policy or preference.
The foregoing is my opinion only and does not represent any formal or informal interpretation of NFPA standards or the opinion of the NFPA 14 technical committee. [cid:[email protected]] Steve Leyton, President T | 619.255.8964 x 102 | www.protectiondesign.com<http://www.protectiondesign.com/> 2851 Camino Del Rio South | Suite 210 | San Diego, CA 92108 Fire Protection System Design | Consulting | Planning | Training From: August Hoffman [mailto:[email protected]] Sent: Monday, May 1, 2023 12:48 PM To: [email protected] Subject: [Sprinklerforum] help Hello, I am a little confused on calculating PRV hose valves and could use some help getting an answer. I have a standpipe system with two standpipes fed by a pump; the lower floors require PRV hose valves due to higher pressure on the lower floors. We are using the ZurnW5000 PRV hose valves for reference. We need to add a new hose valve on one of the lower floors that require a PRV hose valve. For this we are required to flow 750pgm off that standpipe as well as 250 off the other standpipe. The 750gpm will include the new hose valve. 4 Hose valves all flowing at 250gpm total. So far all good, no confusion. Now the PRV setting is dependent on available pressure, if I were to determine the setting based on just one hose flowing it would be different than if I were to have 4 hose valves flowing. My question is - What do I do to determine the setting? Do I flow one hose at 250gpm to get the setting, then calc all 4 with their individual settings to make sure the system works? Or do I flow 4 hose valves to determine the settings accordingly? My issue is - If I use the setting for just one hose flowing and in the field they need to flow 4 then they will not have enough pressure at that hose. If I use the setting from 4 hoses being flowed and in the field they end up flowing just one hose then there will be too much pressure flowing from that hose. Second question - This mostly is for any AutoSprink users, how would you input these settings? I have tried it 2 ways getting very different results. The first test was setting the minimum pressure @ the PRVs residual pressure (say setting 14 takes my 194psi RES. down to 154psi RES so I set my min. pressure to 154). The second test was to keep my minimum pressure @ 125psi but subtract 154 from 194 and adding 40psi loss to my hose valve. The second test seems to make the most sense to me but I heard to do it both ways from different people. I appreciate any advice. Thank you, August Designer NICET WBS 153613
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