You're welcome J. P.
You can't go wrong with full compliance!
You definitely need the compliment at the bottom of the deck and I assume
the reason NFPA 13 is 'silent' on that is because with unobstructed
construction it screams, "12 INCH MAX DEFLECTOR". :) It took me 30 years to
see activation right. The ceiling is not where the heat changes direction
from up to down but from up to out, in an emergency.
For LH and OH, normal ceiling heights I believe the 'out' is 400-600 F at
5-10 ft/sec.
I liked Allen's write-up. Too bad the book doesn't say ~the depth of the
egg-crate shall not exceed twice the least dimension where the pattern has
five feet to get straightened out in the down direction~.

Brad
On Sep 16, 2016 7:14 AM, "J.P. Merlino/Ing. L.Lagomarsino & Asoc." <
jmerl...@lliconsult.com> wrote:

> 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 skipping.
>
>
>
> 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-bounces@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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