Ceiling Obstructions
“We have an architectural feature attached to the ceiling that looks like an open truss. The top and bottom chords are approximately 5 in. for both dimensions and the web components are 2 in. for the diagonal and 3 in. for the vertical recessed, standard pendent sprinklers are being used. Am I required to apply 8.6.5.2.1.6?” We have reviewed the 2010 edition of NFPA 13 you indicated as the applicable standard. Our informal interpretation is this section is not a requirement. Actually,you are required to comply with two different sections. The top chord must satisfy section 8.6.5.1 and the web components must comply with 8.6.5.2. I understand you’ve placed the sprinkler 2-ft away from the top chord that satisfies Table 8.6.5.1.2. One could argue that these are not structural members so 8.6.5.2.1.4 allows you to ignore them. Although that would meet the letter of the standard, it would not meet the intent. As required by 8.6.5.2.1.3, you need to be located away from the obstruction a minimum distance of 3 times the maximum dimension of the obstruction. That would be 9 in. away from the vertical web components and 6 in. away from the diagonal components. The 2-ft separation dictated by the top chord obviously complies with this section. As for 8.6.5.2.1.6, it is an option that allows you to be closer than that dictated by the 3 times rules for many trusses (that being with members no larger than 4 in.). For example, if the truss member was 4 in. you would normally have to be at least 12 in. away. If they were on a 20-in. spacing, this option allows you to be only 8 in. away. It’s 10 in. from the center spacing, but separation distances are measured to the side of the obstruction. ------------ Technical Update is prepared by the Technical Services Dept. of the AFSA: Roland Huggins, a PE registered in fire protection engineering, Vice President of Engineering and Technical Services; and Tom Wellen, a PE registered in fire protection engineering. This is provided with the understanding that the AFSA assumes no liability for this opinion or actions taken on it and they are not to be considered the official position of the NFPA or its technical committees. Copyright 2016, American Fire Sprinkler Association. All Rights Reserved. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.firesprinkler.org/private.cgi/sprinklernotes-firesprinkler.org/attachments/20161205/b702b164/attachment.htm>
