With all this talk about spacing, I think maybe the text within NFPA 13 has been forgotten. Here's what the standard says on the subject of saw-tooth ceilings:
8.6.4.1.3.2* Under saw-toothed roofs, sprinklers at the highest elevation shall not exceed a distance of 36 in. (900 mm) measured down the slope from the peak. A.8.6.4.1.3.2 Saw-toothed roofs have regularly spaced monitors of saw tooth shape, with the nearly vertical side glazed and usually arranged for venting. Sprinkler placement is limited to a maximum of 3 ft (900 mm) down the slope from the peak because of the effect of venting on sprinkler sensitivity. My advice would be to move the sprinkler to a point 3 ft from the peak. That way it will be about 5 ft from the low edge instead of 7 ft, which should alleviate the spray/obstruction/spacing problem somewhat. This is my opinion only and is not intended to represent the NFPA 13 Technical Committee, nor serve as an interpretation of the standard. Larry Keeping -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of [email protected] Sent: November-30-17 6:39 PM To: [email protected] Subject: Re: Saw-Tooth Ceilings I mean, after all, if we can't figure 'half a pattern', how do sidewalls work? I'm out, because... i, I mean Roland and that face, I mean... Oh nevermind - - brad.. Quoting [email protected]: > Sorry John, wrong side of history on this one. > Brad. > > Quoting John Paulsen <[email protected]>: > >> I've been watching this thread all afternoon and what I perceived >> to be a straight forward question has been complicated beyond >> anything I would have thought possible considering the original >> question. For me the bottom line here is that if you submit this >> layout and hydraulic calculations as anything other than the 14' >> dimension on the sloped ceiling, you are going to have to defend it >> to the AHJ. Any plan reviewer worth his salt is going to conclude >> that the vertical portion of the saw-tooth creates an obstruction >> to the spray pattern. That will demand the 7' distance be >> considered half the distance the head has to throw to obtain the >> correct spacing and design density. If this is OH as previously >> stated, in my mind, you are limited to 9' head spacing along the >> line. >> >> However, >> >> If you can get the AHJ and engineer to approve moving the >> sprinklers to the middle of the slope and keep the deflector above >> 12" from the highest point of the ceiling and in conformance with >> Table 8.6.5.1.2 distances from the obstruction, well then you might >> have a shot at the 15' head spacing along the line. >> >> John Paulsen – SET >> Crown Fire System Design >> 6282 Seeds Rd. >> Grove City, OH 43123 >> P – 614-782-2438 >> F – 614-782-2374 >> C – 614-348-8206 >> >> >> >> >> >> >> -----Original Message----- >> From: Sprinklerforum >> [mailto:[email protected]] On Behalf >> Of Michael Hill >> Sent: Thursday, November 30, 2017 4:26 PM >> To: [email protected] >> Subject: RE: Saw-Tooth Ceilings >> >> So you are saying that this is a series of 15 sloped ceilings one >> after the other, not a single obstructed saw tooth ceiling. >> >> I am not trying to be argumentative. I am trying to convince myself >> that what I am being told to do is correct. >> >> Mike Hill >> >> >> -----Original Message----- >> From: Sprinklerforum >> [mailto:[email protected]] On Behalf >> Of [email protected] >> Sent: Thursday, November 30, 2017 4:02 PM >> To: [email protected] >> Subject: Re: Saw-Tooth Ceilings >> >> 23.4.4.6 Deisign Densities >> 23.4.4.6.2, and for backup- >> 23.4.4.6.5. >> You don't have walls Michael, you have a sloped ceiling. >> The down-slope 'half' of the pattern is obstructed, be it sawtooth >> or not :). >> Brad. >> >> Quoting Michael Hill <[email protected]>: >> >>> That section explains what to do once the maximum area of protection >>> is determined. I am still not convinced. >>> I agree that plenty of water is going to get to the fire, if needed. >>> More so as this is a UFC project, HC-2 occupancy, dry system, >>> 0.20/3500. >>> >>> Suppose there were walls that extended down to the floor at each end >>> of the ceiling that created a compartment (which is how I am viewing >>> this situation). In this case the compartment would be 240' x 8'. >>> 8.5.2 tells me to take the distance from the wall, double it and >>> multiply by the distance between sprinklers in the other direction. >>> No mention of if the area is broken down into smaller compartments. >>> >>> Does anyone know of a section in NFPA-13 that allows me to ignore the >>> obstruction when determining area of protection per sprinkler. >>> >>> This is how I look at things when I do not agree with them. I figure I >>> am sitting on a witness stand somewhere (after the fire the destroyed >>> the building) and some insurance company's' lawyer is saying "point to >>> where it says you can do that". >>> >>> Mike Hill >>> >>> -----Original Message----- >>> From: Sprinklerforum >>> [mailto:[email protected]] On Behalf Of >>> [email protected] >>> Sent: Thursday, November 30, 2017 2:34 PM >>> To: [email protected] >>> Subject: Re: Saw-Tooth Ceilings >>> >>> I'm with Ron. >>> See NFPA 13-2016 >>> 23.4.4.6.2. >>> Brad. >>> >>> Quoting Ron Greenman <[email protected]>: >>> >>>> I'll agree the sprinkler knows nothing, but that is irrelevant. We >>>> are working with a mathematical model that will, if all the rules are >>>> followed, give us a reasonable degree of confidence that it will >>>> perform to the design intended, which is, in this case, to keep a >>>> fire contained within the most demanding design area (or any other >>>> similar, but less demanding >>>> area) for a specified duration. So for OH I can space my sprinklers >>>> along the ceiling at a MAXIMUM of 15 ft apart, in any direction >>>> perpendicular to the walls, which is a maximum square footage per >>>> sprinkler of 225 square feet, and a MINIMUM of six feet between them >>>> for a total square footage of 36. So given Mike's layout, he is well >>>> within the parameters of this rule. >>>> Now though we run into another rule which states we cannot EXCEED 130 >>>> square feet of floor area per sprinkler in OH so if we run our >>>> sprinklers at 15' apart on the line we can have a MAXIMUM distance >>>> between lines a fraction over 8.5 feet. Since the sawtooth creates a >>>> "compartment," so to speak, because of the obstructive nature of the >>>> "wall" the "compartment" >>>> distances are 8x15 per sprinkler so he is well within the spacing >>>> rules regarding "throw," and since his horizontal space coverage area >>>> at the floor is less than 130 sqft per sprinkler he is within the >>>> area limitation for OH. His density will be a minimum of 0.15 >>>> gallons/min/sqft and presuming he has enough pressure to push that >>>> quantity of water through the system to the 13 (before adjustments to >>>> the design area, if any) design sprinklers the system will p[erform >>>> as desired. Back to the ignorant sprinkler. Will it adjust to the >>>> 1.0'x7.5'x7.0'x7.5' layout and deliver exactly 0.15 gpm to each >>>> square foot per minute? Of course not. What will happen though is the >>>> system will supply enough water to up to 13 sprinklers anywhere in >>>> the system to meet the design parameter (containment of the fire to >>>> no more than 1500sqft). We can feel confident about this since >>>> sprinkler systems have been doing so for over a hundred years both in >>>> pipe schedule and hydraulically designed configurations. In every >>>> system, there is a prize and that is containment or suppression of a >>>> fire. There are several design methods to obtain the prize and 13 is >>>> merely a prescriptive set of rules to get us there. As long as we >>>> follow the rules we'll be alright. If we want to play mathematician >>>> or fluid dynamicist then we'll cease to be layout technicians and >>>> we'll get distracted and our eyes will stray from the prize. >>>> >>>> On Thu, Nov 30, 2017 at 9:33 AM, Nick Maneen <[email protected]> wrote: >>>> >>>>> You are correct. The sprinkler does not know it needs to throw >>>>> water in mainly one direction. It will be 15x14 >>>>> >>>>> >>>>> >>>>> *Nick Maneen, SET * >>>>> >>>>> *c* 704.791.7789 <(704)%20791-7789> >>>>> >>>>> >>>>> >>>>> *From:* Sprinklerforum >>>>> [mailto:[email protected]. >>>>> org] *On Behalf Of *Michael Hill >>>>> *Sent:* Thursday, November 30, 2017 12:30 PM >>>>> *To:* [email protected] >>>>> *Subject:* RE: Saw-Tooth Ceilings >>>>> >>>>> >>>>> >>>>> Yes, the actual floor area is about 120ft² per sprinkler. Each >>>>> sprinkler has to spray 7’-0” towards the next line. The next >>>>> sprinkler is within 1’-0” of the vertical portion of the ceiling >>>>> (which I am considering an >>>>> obstruction) and will not spray any further in that direction. The >>>>> water will hit the obstruction and fall straight down. I know the >>>>> sprinklers can cover that 7’-0” spray, but I need to make sure it >>>>> does so at the correct density. So for hydraulic purposes is the >>>>> spacing considered 120ft² or is it 210ft². >>>>> >>>>> >>>>> >>>>> My take is that the sprinkler is 7’-0” form a wall or obstruction, >>>>> as the sprinkler has to spray 7’-0” to cover to the low portion of >>>>> the saw-toothed ceiling. L=14 and S=15. So hydraulically that >>>>> sprinkler has to cover 210ft². I would like to say it is covering >>>>> 120ft² but I need to see where in NFPA-13 that it says I can do so. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> Mike Hill >>>>> >>>>> >>>>> >>>>> *From:* Sprinklerforum >>>>> [mailto:[email protected]. >>>>> org <[email protected]>] *On Behalf Of >>>>> *Ron Greenman >>>>> *Sent:* Thursday, November 30, 2017 12:09 PM >>>>> *To:* [email protected] >>>>> *Subject:* Re: Saw-Tooth Ceilings >>>>> >>>>> >>>>> >>>>> If I'm understanding your description and question properly you are >>>>> covering about 116-117 sqft of floor area if one considers the 1'8" >>>>> rise at the tip of the tooth an obstruction, which I would, and your >>>>> "throw distance" along the slope is at 0-360 degrees=7.5'/90 >>>>> degrees=7.0'/180 >>>>> degrees=7.5 degrees/270 degrees=1.0'. That puts you within coverage >>>>> rules for OH, and throw range rules for SS sprinklers. >>>>> >>>>> >>>>> >>>>> On Thu, Nov 30, 2017 at 8:33 AM, Michael Hill >>>>> <[email protected]> wrote: >>>>> >>>>> I am working on a firing range that is going to have a saw-tooth >>>>> type ceiling installed. I have a question about determining maximum >>>>> protection area per sprinkler. >>>>> >>>>> >>>>> >>>>> The vertical portion is 1’-8” tall with the distance from the high >>>>> point to the low point being 8’-0”, measured along the slope. >>>>> Sprinklers need to be spaced close to the vertical portion of the >>>>> ceiling, to protect them from stray projectiles. The sprinkler will >>>>> end up being about 7’-0” from the low point of the ceiling, measured >>>>> along the slope. The sprinklers are about 8’-0” apart, but with a >>>>> 1’-8” vertical portion of the ceiling between them. Sprinklers are >>>>> spaced 15’-0” apart along the branchline. See attached sketch (if it >>>>> came through). >>>>> >>>>> >>>>> >>>>> Would the spacing be 15’ x 8’ or would it be 15’ x 14’? >>>>> >>>>> >>>>> >>>>> I feel it should be 15’ x 14’ as any individual sprinkler needs to >>>>> cover 7’-0” in one direction, measured along the slope. I feel the >>>>> vertical portion of the ceiling is an obstruction and can almost >>>>> been interpreted as a wall that extends to the floor. I also thought >>>>> I needed to increase my design area for sloped ceiling for this >>>>> situation, but have since been shown the commentary in the handbook >>>>> that explains why it is not required for saw-toothed ceilings. >>>>> Maybe I am wrong about the spacing as well. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> Mike Hill >>>>> >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> Sprinklerforum mailing list >>>>> [email protected] >>>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler. >>>>> org >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> >>>>> Ron Greenman >>>>> >>>>> >>>>> [email protected] >>>>> >>>>> 253.576.9700 <(253)%20576-9700> >>>>> >>>>> >>>>> >>>>> The Universe is monstrously indifferent to the presence of man. >>>>> -Werner Herzog, screenwriter, film director, author, actor and opera >>>>> director (1942-) >>>>> >>>>> _______________________________________________ >>>>> Sprinklerforum mailing list >>>>> [email protected] >>>>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler. >>>>> org >>>>> >>>>> >>>> >>>> >>>> -- >>>> Ron Greenman >>>> >>>> [email protected] >>>> >>>> 253.576.9700 >>>> >>>> The Universe is monstrously indifferent to the presence of man. >>>> -Werner Herzog, screenwriter, film director, author, actor and opera >>>> director (1942-) >>> >>> >>> >>> _______________________________________________ >>> Sprinklerforum mailing list >>> [email protected] >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl >>> er.org >>> >>> _______________________________________________ >>> Sprinklerforum mailing list >>> [email protected] >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl >>> er.org >> >> >> >> _______________________________________________ >> Sprinklerforum mailing list >> [email protected] >> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >> >> _______________________________________________ >> Sprinklerforum mailing list >> [email protected] >> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >> _______________________________________________ >> Sprinklerforum mailing list >> [email protected] >> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
