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
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