We will most likely put two levels of sprinklers, one over and other at ceiling 
level. Maybe the ceiling level shall be the intermediate level type to avoid 


As stated by Mr. Seidel, we are in the performance field here. I do not find 
that the standard gives the egg-crate (those that obstruct water discharge) a 
"ceiling effect" to hot gases and waive the upper level of sprinklers.


AHJ will not give opinion or requirement on this issues. We follow full 
compliance with NFPA 13. 


Thanks for all replies.


J.P. Merlino




De: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] En 
nombre de AKS-Gmail-IMAP
Enviado el: viernes, 16 de septiembre de 2016 12:24 a.m.
Para: sprinklerforum@lists.firesprinkler.org
Asunto: Re: Open-Grid Ceilings - Egg crate


As we all well know, we are not supposed to apply conventional wisdom in regard 
to the standard. We are to do what is says, period. For example the thought, 
“there is nothing there to burn”, is forbidden because a premise to the 
standard is that there already is a fire. The standard is about how we are to 
deal with it. The egg-crate question is one part of the standard where we are 
forced to apply a conventional wisdom opinion. Perhaps the unanswered root 
question is, “At what level of perforation does a perforated ceiling cease to 
be a ceiling with ceiling level only sprinklers required to become a ceiling 
with sprinklers required both at the ceiling and above the ceiling?”. The 
standard actually appears to approach this subject in reverse. “We allow 
sprinklers above a perforated ceiling, and here is the distance and spacing 
etc., but when that ceiling gets to be like this, then sprinklers are also 
required at the ceiling plane.” Can we turn that around to define when a 
ceiling is no longer a ceiling? A 69% open ceiling is a ceiling? A 71% open 
ceiling is not a ceiling? 


We already know how to deal with clouds, at least better than before, and we 
also know a little better how to deal with “small openings” for HVAC, but there 
is no guidance for some ceilings now in vogue, especially the thin sheet metal 
ceilings, that by the way, are available in open-ness much higher than 70%. The 
egg-crate in question sounds like it flat out flunks the sprinklers required 
only above standard even though conventional wisdom knows sprinklers far above 
the ceiling would not have their distribution obstructed, because it is 
vertical when it meets the ceiling and of course, all water would drip through 
at the rate it is being applied. Would a metal ceiling arrest some flames 
thereby slowing down the upper level activation? Maybe, but that may not be to 
the benefit of ceiling level sprinklers at conditions near the flunk boundary.


The tag team member to this very same topic is the question, “Now that I have 
this perforated ceiling that flunks the ok egg-crate test, how far away do I 
carry these above ceiling sprinklers? 24 feet all around, seriously?” 


Maybe the cloud committee is actively performing tests for these conditions or 
perhaps these conditions have been tested.


Allan Seidel

St. Louis, MO



On Sep 15, 2016, at 4:59 PM, J.P. Merlino/Ing. L.Lagomarsino & Asoc. 
<jmerl...@lliconsult.com> wrote:


Dear Sirs:

NFPA 13 Ed. 2016 - 8.15.14


If we have an open grid egg-crate that meets 70% open space but the depth of 
the material (2 in) exceeds the least dimension (1 in) it does not comply with 
the allowance not to install sprinkler beneath and we must install in the 
egg-crate (or beneath).

But the standard is silent on what to do with the space over the egg-crate. 
Shall we have two layers of sprinklers, one in the egg-crate and the other over 
the egg-crate as if the egg-crate does not exist?

I appreciate your thoughts or if we are missing something.

best regards

J.P. Merlino




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