the reason it should stay in section 8.6 is because it is the hybrid
part of the residential design whereby the 0.1 must also be checked
(and that part is being treated like a spray sprinkler). Seems a
little history lesson is warranted regarding WHY the 0.1 was added.
Long,long ago ok only about 10 yrs starting with TIA 99-1.
If you remember back when there was no minimum density on residential
sprinklers and effective densities were down around 0.03 gpm/sf, FM
did some testing and had some of the test fail miserable. This lead
to two primary changes. One was that the foam in the fire test was
standardized for heat release rate and the dual discharge requirement
of 0.1 gpm/sf and the listing criteria was born. The reason for the
0.1 was not due to the failure of the test (since that was fixed by
the changes to the fire test standard). It was due to the realization
that the residential sprinkler had been made acceptable for high rise
buildings (residential of course) BUT THE FIRE TEST HAD A MAXIMUM
DURATION OF 10 MINUTES. Since then, the duration has been extended
(to 30 minutes I believe) but at the time that posed a problem. Enter
the old faithful light hazard density to rescue the day.
This sprinkler was now being designed for both the listing residential
criteria (typically close to 0.05) and the good ole 0.1 following the
SxL rule. Since the 0.1 was being evaluated like a spray sprinkler,
why would it not be reasonable and prudent to apply not just the SxL
rule but all spray sprinkler spacing rules? It was reasonable and
prudent so it became criteria.
Roland
On Nov 1, 2010, at 5:13 PM, Ben Young wrote:
That makes no sense. How did the committee allow a reference to SSU/P
spacing criteria under residential sprinkler design. It just makes so
little sense. I was thinking about it as I was driving home... If
this is
truly the intent of the code (to average the spacing of residential
heads in
small rooms) the correct (in my opinion) IE, non-confusing way to do
this
would be to put the same language in the Chapter 8 section about
residential
sprinklers or pull 8.6.2.1.2 back into 8.5 or anything other than
referencing residential design methods from SSU/P spacing rules.
I can't be the only person who thinks that doesn't make a lot of
sense, can
I?
I'm also shocked that I never noticed this before. Believe me, I
checked
the 2010 edition, thinking maybe it was a mistake that got
rectified, etc.
So I guess part of this is sour grapes too.
Benjamin Young
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