Matt, Originally there were only extra and ordinary hazard systems and there area per sprinkler coverage was 60 sqft and 90sqft respectively (John World's original rules for sprinkler layout). That area was later increased (I don't know when) the 100 sqft and 130 sqft we know today. At that time all systems were pipe scheduled and the schedule went to 400 sprinklers. 100 x 400 = 40,000, & 130 x 400 = 52,000, hence the maximum square footage per system. Later we got light hazard (the forties I think) and the storage limitations. Why light hazard is also 52K may just be because no one remembered where the original numbers came from (160 x 400 = 64,000 & 225 x 400 = 90,000 makes more sense to me) but it was never the myth of not wanting to shut down more than 52,000 sqft at a time. That is a piece of inductive logic that doesn't make sense, not as a pick-a-number number nor as one hazard without water being more of a danger than another, even when you forget that NFPA doesn't work in what ifs. NFPA 13 also doesn't address maintenance, alterations or repairs. That, I believe, is in the 901.7 of the fire code under systems out of service.
I might ask him if that extra 8000 sqft that you can't see from where you're working is more dangerous than the other square footage you can't see, especially since he agrees that 60K will work as good as 52K when it's operational. Ron Greenman [email protected] 253.576.9700 The Universe is monstrously indifferent to the presence of man. -Werner Herzog, screenwriter, film director, author, actor and opera director (1942-) On Tue, Aug 14, 2018 at 2:20 PM Matt Grise <[email protected]> wrote: > I was recently discussing the max system size issue with a building > official. In this specific application we are requesting that the AHJ allow > us to use a 60,000 square foot maximum size for ESFR systems in a big box > warehouse. > > > > I have commentary directly from FM (in addition to FM2-0) that says “The > size of the sprinkler system is not expected to affect the effectiveness of > the sprinkler system as long as the system is designed properly for the > occupancy.” > > > > The AHJ’s response was: “The system will work as well when the system is > in operation, but when you turn it off for maintenance, there is a greater > risk of fire since there is more area out of service.” > > > > I had assumed that the greater system sizes result in equal system > effectiveness on the whole – in the sense that there is no evidence that > the greater system area causes more fire losses even when maintenance > downtime is factored into the equation. I had even thought that perhaps > system performance on the whole would be improved since there are fewer > control valves in the building that could be left closed (when they should > be open). > > > > But, I have heard that “assuming” things can have negative consequences… > > > > On that note, I wanted to reach out and see what insight anyone might > offer on system performance related to system size. Do large sprinkler > systems perform equally only when they are operating properly – or do they > operate properly (and perform equally) just as well, historically, as > smaller systems? Has larger system size ever been faulted as the cause of a > loss? > > > > Any insight/research/documentation would be great! > > > > Thanks, > > > > Matt > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >
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