I believe this is one of those things that has unintended consequences. As I heard urban legend rumors, the idea was for something like a loading dock or something. That if you added additional flow to the main, that if adjacent sprinklers were to activate that the system would be sized to handle the additional sprinklers. Say you have a 500 sq ft loading dock that has a 100 gpm demand. The interior is also OH2. Well, if you add the extra 200 gpm at the point where it connects to the interior system, then if the fire expanded to the interior the system would have capacity for the extra sprinklers. This could have just been urban legend.
But, if you follow it literally, you are to add the flow at the end of the main in question. That means you would very rarely use smaller dry valves or such any longer. One that comes to mind is these tire storage carousels. They are like 0.6/5000 for that tire arrangement. But if you only have a single carousel, why do we need 3000 gpm demand. That section in question would require the 3000 gpm. So, it has been known to kill a couple projects I am aware of. Travis Mack, CFPS, CWBSP, RME-G, SET Engineering Manager MFP Design 3356 E Vallejo Ct Gilbert, AZ 85298 NEW EXTENSION: 480-505-9271 ext. 700 NEW MOBILE: 480-272-2471 mailto:[email protected] www.mfpdesign.com From: Sprinklerforum <[email protected]> On Behalf Of Prahl, Craig/GVL via Sprinklerforum Sent: Thursday, December 10, 2020 9:33 AM To: [email protected] Cc: Prahl, Craig/GVL <[email protected]>; James Litvak <[email protected]> Subject: RE: [EXTERNAL] 23.4.4.2.5: What is the purpose and how does it apply? Very good question. I've read discussions on this issue recently as well and really wonder what was the thought process behind including a non-existent flow value in the system design and calculations. I would love to hear the rationale for this section. Craig Prahl | Jacobs | Group Lead/SME - Fire Protection | 864.676.5252 | mailto:[email protected] | http://www.jacobs.com 1041 East Butler Road Greenville, South Carolina 29606 -----Original Message----- From: Sprinklerforum <mailto:[email protected]> On Behalf Of James Litvak via Sprinklerforum Sent: Thursday, December 10, 2020 10:45 AM To: mailto:[email protected] Cc: James Litvak <mailto:[email protected]> Subject: [EXTERNAL] 23.4.4.2.5: What is the purpose and how does it apply? I've just been introduced to section 23.4.4.2.5 (2016). In my particular situation, I have an EH2 refueling building (0.4 / 2,500) that is 2,268 sq.ft. in its entirety. The flow from my calc came out to 998 gpm, so I was told by my coworker who reviewed my plans not to worry about the extra 2 gpm that would need to be added to meet the 0.4 * 2,500 = 1,000 gpm minimum requirement. However, this is a dry system. So I asked my coworker if 23.4.4.2.5 applies to the 2,500 sq.ft. minimum per Figure 11.2.3.1.1, or if it applies to 3,250 sq.ft. after I increase 30%, which would require a minimum of 1,300 gpm. Not only are we unsure of that, but that got us wondering what the exact purpose of this section is, and how it would apply to other situations. If I have an EH2 building that is 300 sq.ft. and protected with 3 sprinklers on a dry system, do I need to design the riser and cross main to handle 1,000 (maybe 1,300) gpm? That seems insane. I've read through some threads on this forum, and also some websites, and the example often given is that of a paint booth. One example considers a paint booth protected by 6 high temp. sprinklers with a demand of 250 gpm. It says that 550 gpm would need to be added to the cross main to make up the rest of the required 0.4 * 2,000 = 800 gpm minimum demand. But why? If a sprinkler in an EH2 area is required to provide at least 0.4 gpm/sq.ft., and they are doing that, what is the purpose of providing more flow? The hazard remains the exact same, so why are we required to overdischarge, when the actual potential risk is lower than a larger area? Theoretically, my 2,268 EH2 building is a lower risk than a 4,000 EH2 building that is otherwise exactly the same. Yet if I go by 1,300 gpm as my minimum required demand, I will be providing way more water per sq.ft. in the smaller building than in the larger building. So unless I am completely missing something here - or a few things - I am totally baffled. I'm hoping someone can help me understand all this. Thanks. James Litvak _______________________________________________ Sprinklerforum mailing list mailto:[email protected] https://urldefense.com/v3/__http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org__;!!B5cixuoO7ltTeg!VO4VMIa80RQe-j4UNMGpQfWegM4j7sqJxkum95ViMHfpMByNGKHBmRo-w194r6keuQ$ ________________________________ NOTICE - This communication may contain confidential and privileged information that is for the sole use of the intended recipient. Any viewing, copying or distribution of, or reliance on this message by unintended recipients is strictly prohibited. If you have received this message in error, please notify us immediately by replying to the message and deleting it from your computer. _______________________________________________ Sprinklerforum mailing list mailto:[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
