I think it is more of a check and balance than a requirement. If you properly calculate 1.2*(Design Area), take that divided by your maximum head spacing "S" and you come up with X.XX number of heads. The only thing you do with this number is make sure you have at least that many. If you don't you go back and start over. If you do the you move on.
Thanks, Eric Tysinger CET NICET III - 108988 Designer Wayne Automatic Fire Sprinklers, Inc. 4370 Motorsport Drive Concord, NC 28027 p: (704)782-3032 x1751 f: (704)795-6838 C: (239)633-9703 -----Original Message----- From: sprinklerforum-boun...@firesprinkler.org [mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Bob Knight Sent: Tuesday, April 20, 2010 4:11 PM To: sprinklerforum@firesprinkler.org Subject: RE: Calc Area Chris, You stated that "There is no requirement for any number of heads", I don't agree with this statement based on section 22.4.4.1.1.2 (2007) which directs us to rounding the number of sprinklers required within the 1.2 zone. So, based on this there IS a minimum number of sprinklers required within the 1.2 zone as the ANNEX material clarifies in the example given on page 346. The difference lies within the fact that the minimum number of sprinklers is a fluctuating number based on the S within the design area for the area under consideration verses ESFR's which are assigned a minimum number of 4. Bob -----Original Message----- From: Chris Cahill [mailto:chr...@sentryfiremn.com] Sent: Tuesday, April 20, 2010 1:08 PM To: sprinklerforum@firesprinkler.org; b...@firebyknight.com Subject: RE: Calc Area I'm confused. Why are you averaging? You need 46.5' along the BL, right? There is no requirement for any number of heads (except for ESFR and other head count designs). Other than saying you have to work in whole sprinkler heads the code process of design area selection never mentions head counts, right? The introduction of S to create a head count related to the 46.5' comes from the annex and is an EXAMPLE for ONE particular arrangement. It certainly isn't there as an example for any other situation. If I have varying lengths between the heads I check, starting at the wall, the number I need to get to 46.5' with a RULER. This establishes the minimum number of heads I will calculate, call it calc #1. Then I work my way down the line with my RULER and check the next series of heads minus the last head on the line. If I get a head count higher than the first that becomes a second calc I HAVE to do because I don't readily know if the length or the extra head is more of a hit in the calcs. I check all the possible continuous heads for the 46.5'. Seems easier to me to than doing a bunch of math which if right is by coincidence or if wrong has no correlation to code. 46.5' is the only right answer. And note you absolutely have the ability to shift the heads on the line if you come up real close and have some area left in the sq.ft./head limits. Measure 46.4' to the center of 2 heads. Shift one an inch and save yourself a head on that calc. *****BUT***** that inch needs to be checked closer to the main as you probably will get caught someplace with an extra head. Hydraulically, it usually is better to take the hit for the extra head over the main than at the end of the BL. Chris Cahill, P.E. Fire Protection Engineer Sentry Fire Protection, Inc. 763-658-4483 763-658-4921 fax Email: chr...@sentryfiremn.com Mail: P.O. Box 69 Waverly, MN 55390 Location: 4439 Hwy 12 SW Waverly, MN 55390 No virus found in this outgoing message. Checked by AVG - www.avg.com Version: 9.0.814 / Virus Database: 271.1.1/2823 - Release Date: 04/20/10 06:45:00 _______________________________________________ Sprinklerforum mailing list Sprinklerforum@firesprinkler.org http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: supp...@firesprinkler.org To Unsubscribe, send an email to:sprinklerforum-requ...@firesprinkler.org (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list Sprinklerforum@firesprinkler.org http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: supp...@firesprinkler.org To Unsubscribe, send an email to:sprinklerforum-requ...@firesprinkler.org (Put the word unsubscribe in the subject field)
