One preaction system control valve is allowed to serve no more than 1,000 sprinklers.
If you have 1,650 sprinklers then you would need at least two separate preaction systems. Breaking this large of a building up into three or even four systems might be a very good idea. You might also consider separating the system run-ins into the building so that all systems are not fed from one single source. Depending on how this building is arranged and its size, you may want to or have to consider more than two systems. NFPA 11.2.3.2.5 doesn't mention the increase area for single interlock systems, it specifically mentions double interlock. Don't confuse this with 12.5.1 as the 30% increase IS required for preaction systems in storage applications using density/area control mode sprinklers. NFPA 13 2007, 11.2.3.2.5* Dry Pipe and Double Interlock Preaction Systems. For dry pipe systems and double interlock preaction systems, the area of sprinkler operation shall be increased by 30 percent without revising the density. >From the NFPA 13 Handbook 11.2.3.2.5 The 30 percent area increase rule does not apply to preaction systems other than double interlock preaction systems. Even though the pipe has no water in it, the delay in operation of non-interlock and single interlock systems is minimal, because the detection device typically responds to the fire sooner than the sprinkler. See the commentary following 7.3.2.1. >From the NFPA 13 Handbook 7.3.2.1 Preaction systems are addressed in 7.3.2.1. Both the single interlock and non-interlock systems require only one event to occur before water is admitted to the system. The single interlock system is activated by the release of the detection system. Sprinkler activation does not affect this function. The non-interlock system is activated if either the detection system or a sprinkler operates. The double interlock preaction system requires two events to occur before water is admitted to the system. One event consists of the activation of a device installed on the supplemental detection system. The other event includes the operation of a sprinkler that causes the maintained air pressure in the system to fall to a predetermined level, which is similar to that of a dry pipe system. When one of these events occurs, the system activation valve goes into a preset position. When the second event occurs, the valve opens, and water enters the system. Water does not enter the system until both events occur. These two events can occur in any order and result in the same outcome. Craig L. Prahl, CET Fire Protection Specialist Mechanical Department CH2MHILL Lockwood Greene 1500 International Drive PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 [email protected] http://www.ch2m.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of sam b Sent: Monday, June 29, 2009 7:49 AM To: [email protected] Subject: Preaction system : need help Hiii friends got a doubt regarding Preaction systems (specifically single interlocked system). I am designing a sprinkler system for a cultural /exhibition hall where the client needs preaction system for the entire area, The area is around 14,100m2(1,52,000 ft2). There are 4 no. risrers and I have considered 4 alarmcheckvalves for the total area and total sprinklers in the area is about 1650. from NFPA 13 7.3.2.2 , I found" not more than 1000 sprinklers shall be controlled by one preaction valve." does that mean u can have multiple zones controlled by single preaction valve? In my case how many preaction valves should i consider, Is it 2 nos considering maxm 1000 per preaction valve.? or 4 nos considering one along with each alarm check valve.? Do I need to consider extra 30% that is to be considered for dry systems in my calculation?? Hope someone will clarify this for me.. Thanx in advance Sam _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
