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 [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
