Steve,
I'm not sure I agree. Aside from what the book says, I look at this
type of situation and I have a couple issues with it. Sprinklers at
the deck are typically uprights directly off a branch line (or
perhaps a short sprig). The pendent sprinklers may be fed by swing
joints or flexible drops, which could make those sprinklers more
hydraulically demanding. This could make the area below the clouds
the most hydraulically demanding. However, I can't say if the ceiling
jets on a cloud would be sufficient to activate sprinklers below them
without the possibly activating sprinkler above. Without fire tests
or other research to verify different, I would assume that some
combination of sprinklers at the deck and below the cloud would
operate. Since we are charged by NFPA 13 with calculating the most
hydraulically remote area, my conclusion is that both levels would
have to be calculated to conservatively predict what would actually happen.
Typically, sprinklers below obstructions over 4 ft tend to be
relatively widely spaced and be relatively small compared to the
ceiling area. This may not necessarily hold true for ceiling clouds,
especially given the arrangements I have seen. The dynamics of the
clouds could be very different than that of a few sections of ductwork.
We need some research and testing and hopefully it will happen before
a significant fire loss.
Todd
At 06:51 PM 2/6/2009, you wrote:
Do not concur. If the cloud condition is such that your best judgment
is to provide a complete complement of sprinklers above, then you would
calculate either above or below the clouds, as we always have for
obstructions like ducts and in accordance with the exception spelled out
in 22.4.4.6.3 (2007 ed.). We often use SSP's above clouds and EC's
below, especially when existing sprinklered buildings are being
re-modeled or there's tenant turnover in an office shell, so sometimes
it's two separate calc' areas but not a concurrent calculation of two
different complements of sprinklers.
Steve Leyton
Protection Design & Consulting
San Diego, CA
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: Friday, February 06, 2009 2:21 PM
To: [email protected]
Subject: Re: CEILING CLOUDS - AGAIN
And calculate both levels of sprinklers. You have no idea what is really
going to happen on a fire.
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: "Jeff Hewitt" <[email protected]>
Date: Fri, 6 Feb 2009 16:07:37
To: <[email protected]>
Subject: RE: CEILING CLOUDS - AGAIN
Travis,
Since we have no specific guidance on this topic, my recommendation is
that
you must protect to deck first, and deal with the obstructions second.
With this criteria, I would recommend both above and below the clouds.
Just my thoughts
Jeff Hewitt, PE, SET, SFPE (Professional Member)
Corporate Engineer
241 Hughes Lane
St. Charles, MO 63301
636-946-0011
636-946-5172 (fax)
314-574-6989 (cell)
Fire Sprinklers Save lives.
Can You Live Without Them?
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Travis
Mack,
SET
Sent: Friday, February 06, 2009 3:50 PM
To: [email protected]
Subject: CEILING CLOUDS - AGAIN
I have a project with lots of floating clouds. The clouds slope with
the
roof deck and are 1' below the roof deck. If I place a sprinkler in the
cloud, is one req'd in the space above the cloud? I would normally put
sprinklers above the clouds, but with the deflector already at 12" below
the
roof deck based on the cloud height, do you really need the sprinklers
above
the clouds?
Please feel free to call if you have any questions or comments.
Travis Mack, SET
<mailto:[email protected]>
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
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