American Fire Sprinkler Association 12750 Merit Dr., Suite 350 * Dallas TX 75251 Ph: (214) 349-5965 Fax: (214) 276-0908
------------------ TECHNICAL UPDATE FEBRUARY 17, 2010 ------------------ In a 13R system where the balcony is protected per the IBC, the wet-pipe branch line drops down from above the ceiling within the 6 inch exterior wall to a dry horizontal sidewall sprinkler. The drop nipple is completely wrapped in insulation. The barrel length is approximately 3-1/2 inches. This area is assigned a lowest temperature below -20 degrees F. Does this installation comply with NFPA 13, 2007 section 8.4.10? We have reviewed 13, 2007 Edition that you indicated as the applicable standard. Our informal interpretation is that it appears that it does not comply with NFPA 13 on freeze protection requirements. There are actually two freeze protection criteria that are a problem. The first is that all portions of a sprinkler system must be protected against freezing. To accomplish this, all pipe containing water must be exposed to air that is at or above 40 degrees F or protected against freezing (see 13:8.16.4.1.1). This can be accomplished using a dry pipe or antifreeze system or heat tracing (although branch lines can not yet use heat tracing since there is no listed product on the market). Although the insulation on the outside of the drop nipple reduces its exposure to the cold, having insulation on the inner portion of the drop nipple reduces its exposure to heat. Insulation alone does not stop a pipe from freezing but must be used in conjunction with exposure to heat. Technically, it is a matter of heat transfer and if the transferred heat to the pipe is greater than the transferred loss of heat from the pipe, the pipe will not freeze. So in mild climates with very short periods of freezing temperatures, it may not be a problem. But in more severe climates with sustained cold periods, insulation alone simply increases the time required for the pipe to freeze. The second issue is that there are barrel length requirements to avoid freezing caused by the cold being conducted through the sprinkler barrel to its connection to the pipe containing water (see 13:8.4.10.1). This means that part of the sprinkler barrel must be exposed to heated air inside the building. The requirement for the barrel to be exposed to heated air is explicitly stated in the manufacturer’s installation instructions, as is the minimum exposed length. One manufacturer specifies for exposure to -20 degrees F a minimum of 12 inches of barrel when exposed to air that is at least 40 degrees F. The length increases to 18 inches for -40 degrees F. ----------------- Technical Update is prepared by the Technical Services Dept. of the AFSA: Vice President of Engineering and Technical Services Roland Huggins, a PE registered in fire protection engineering; Phill Brown, a NICET IV certified automatic sprinkler technician and NFPA Certified Fire Protection Specialist (CFPS) and Tom Wellen, a degreed fire protection engineering technologist. 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 © 2010, American Fire Sprinkler Association. All Rights Reserved -------------------------- If you’d rather not receive future faxes from AFSA, fax your removal request to Amy Sweeney at Efax (214) 242-3155 or call toll free (888) 839-4830 or send e-mail request @ [email protected]. Please include your company name and the specific fax numbers(s) at which you do not wish to receive faxes from us. Our failure to comply with your request may be unlawful. _______________________________________________ Sprinklernotes mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklernotes
