Ron, First, thanks for replying. But not sure if you understand my question.
NFPA has two restrictions. (1) width (or depth) whichever way you call it, the horizontal distance of the soffit in cross section) maximum 8" (2) The vertical distance from deflector to bottom of soffit is minimum 2" If both these conditions are not satisfied, sprinklers are required at bottom of soffit. The NFPA 13 handbook commentary states the 8" max is to ensure water gets to the back wall. If that is a concern, I think, they should also have a maximum distance from deflector to bottom of soffit. The way it is now, you can have a soffit 8" wide or deep (the horizontal distance) and 5 feet high (vertical distance) and have the sidewall head in the soffit 6" below the ceiling, with no heads below the soffit. The reason I'm asking this question is: could it be NFPA meant MAXIMUM 2" vertical distance, and the error has been carried in the code for many years? -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ron Greenman Sent: August 14, 2007 1:09 PM To: [email protected] Subject: Re: sidewalls in soffits Tony, One should read the text before replying. 8.7.4.1.3.2 says that the distance from the sidewall to the bottom of the soffitt is a minimum 2" or greater than the distance from the ceiling to the sidewall (distance from ceiling to sprinkler = X so distance from ceiling to bottom of soffit is X+2" or more). I think this has to do with pattern development rather than applying water behind the sprinkler. 8" is the maximum width ( I think we, or at least I, have been confusing width with depth) that a soffit can be before it also needs heads below it (8.7.4.1.3.2). I think this verifies the previous assumption since an 8" dead space along the wall is considered here as no problem with standard spray sprinkler applications (what 13 always differs to). I think you get differing values with residential heads due to the necessity for high wall wetting to forestall flashover starting at wall ceiling intersections due to the higher fuel loading in residences along walls. Just a lot of I thinks and I hope those are addressing the question. On 8/14/07, A.P.Silva <[EMAIL PROTECTED]> wrote: > Ron, > > The problem I have is, NFPA gives a minimum distance of 2" from deflector to > bottom of soffit. I don't understand why the minimum distance is critical, > but as you say, that must be how they tested. What I don't understand is, > NFPA does not give a maximum distance, which IMHO is more critical, for > spraying to the back wall. So for a standard non-residential head (for which > the manufacturers' don't impose limits for the maximum distance), it can be > installed anywhere on the soffit, provided the deflector is at a distance > equal or more than 2" from the bottom of the soffit? That's how it sounds to > me. > > Tony > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Ron Greenman > Sent: August 14, 2007 10:46 AM > To: [email protected] > Subject: Re: sidewalls in soffits > > Tony, > > I'm probably wrong or misreading your question but I think the Tyco LF > II maximum would be based on their sprinkler performance under these > conditions whereas NFPA criterion is the minimum performance standard. > This bears out when you see NFPA has a minimum standard but no maximum > while Tyco LF II has both (beyond the standard) and QR merely meet the > standard. All are restricted to 8" maximum lintel depth but presumably > anybody that could prove there sprinkler performs per UL/FM at a 10' > (is their a tongue in cheek keyboard configuration similar to the I'm > making a joke :-) design?) lintel depth could have it listed thus. > > On 8/13/07, A.P.Silva <[EMAIL PROTECTED]> wrote: > > > > NFPA 13, 2002; 8.7.4.1.3.1 states deflector to bottom of soffit to be > > MINIMUM 2 inches. The commentary in the handbook says depth of soffit is > > limited to 8 inches, to project water to the back wall. So wouldn't the > > deflector to bottom of soffit also affect spraying to the back wall, and > > thus be limited to MAXIMUM 2 inches? There is no comment in the handbook > for > > the restriction of the deflector height above the bottom of the soffit. > > > > If not, is there a maximum? > > > > Tyco Series LFII, residential sprinkler design guide, figure 4, part 2, > > limits MAXIMUM distance to 4 inch. (Tried checking design guides in the > web > > for Reliable, Viking and Victaulic for comparison but for some reason been > > unable to download them, maybe my server is currently too slow) > > > > The problem is residential heads (TYCO LFII) have been installed in an 8 > > inch wide soffit (in a residential corridor), with the deflector 7 1/2" > > above the bottom of the soffit. It clearly violates the TYCO design > > guidelines. I'm looking at recommending replacing with standard q/r heads > > (provided the hydraulics work, of course). Is that an option? > > > > Going by the available info, it should be okay, as NFPA does not give a > > maximum value. However, I am worried whether it is an error in NFPA. > > > > Anyone out there has given this some thought? > > > > Tony > > > > _______________________________________________ > > Sprinklerforum mailing list > > [email protected] > > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > > > To Unsubscribe, send an email to:[EMAIL PROTECTED] > > (Put the word unsubscribe in the subject field) > > > > > -- > Ron Greenman > at home.... > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > > To Unsubscribe, send an email to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > -- Ron Greenman at home.... _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
