Due to changes in the national residential sprinkler standards, the residential market is now more demanding, needing not only an effective sprinkler usually dedicated to a smaller space, but a sprinkler that is subtle and coheres to the residential environment.
Managing to pack these necessities into a sprinkler that complies with the recently updated National Fire Protection Association (NFPA) Standard 13D, Installation of Sprinkler Systems, One- and Two-Family Dwellings and Manufactured Homes; Standard 13R, Installation of Sprinkler Systems in Residential Occupancies Up To and Including Four Stories in Height; and revisions to Underwriters Laboratories (UL) Standard 1626, Standard for Residential Sprinklers, has definitely been a challenging, yet necessary journey.
Changes in Residential Sprinkler DensitiesUntil these recent changes, manufacturers have held a wide variety of listings with applications of residential sprinklers from sprinkler spacings of 12 ft. x 12 ft. to 20 ft. x 20 ft.; and horizontal ceiling heights of 8 ft., to sloped ceilings with a pitch of 8/12 (rise over run) with unlimited ceiling heights. Additionally, discharge densities that had no specified minimums in the UL or NFPA standards resulted in listings as low as .03 gpm/sq. ft. This reduction is significant compared to the minimum density of .09 gpm/sq. ft. density referenced in NFPA 13D in the 1980 to 1999 editions. In 2002, the UL Directory listed 110 models of residential sprinklers with over 600 different applications. Both the NFPA 13D-2002 and NFPA 13R-2002 edition, with an effective date of August 8, 2002, contain a new minimum discharge density of .05 gpm/sq. ft. for all residential sprinkler coverage areas. Although this is a reduction to the minimum densities specified by NFPA 13D and NFPA 13R, it is an increase in flow rates from the special listings manufacturers have obtained from UL over the past 20 years.
Changes in Listing RequirementsThe first residential sprinkler listing was granted to Grinnell's Model F954 in 1981. The listing was based on a maximum coverage area of 144 sq. ft. (12 ft. x 12 ft. maximum spacing). The minimum flow for the F954 was based on the NFPA 13D minimum of 18 gpm for a single sprinkler flow rate and 13 gpm for the multiple (two sprinklers) sprinkler flow rate. These minimum flow rates translate to equivalent .125 gpm/sq. ft. and .09 gpm/sq. ft. densities. All residential sprinklers were required to meet these requirements unless they were listed as equivalent. Beginning in the early 1980s, Central Sprinkler utilized the listing process to provide equivalent protection with lower flow rates combined with greater sprinkler spacing. Soon coverage areas up to 400 sq. ft. (20 ft. x 20 ft.) existed at densities as low as .03 gpm/sq. ft. Extended coverage listings, combined with lower flows, provided the industry with exactly what NFPA 13D was created for-a low cost life safety sprinkler system that allows the evacuation of occupants in the event of a fire in one- and two-family dwellings.
NFPA 13D, Installation of Sprinkler Systems, recognized the use of residential sprinklers in residential portions of NFPA 13 occupancies in 1983. Additionally, NFPA 13R, Installation of Sprinkler Systems in Residential Occupancies Up To and Including Four Stories in Height, first published in 1989, recognized the use of residential sprinklers in multiple (more than two) family residences in buildings up to four stories in height. More and more dependence on the performance of residential sprinklers was expected, including the protection of property rather than just the life safety feature.
In 1999, Factory Mutual (FM) conducted a residential fire test using a UL-listed residential sprinkler. According to the FM report, the listed flows and pressures were inadequate for the FM residential test series, sparking a debate on the adequacy of the current test and installation standards.
Why Did the Changes Occur?This is a frequently asked question, since these residential sprinklers were listed by UL, a nationally recognized laboratory. While residential sprinklers have maintained an impeccably successful field record since their origin, it was also recognized that a level of variability exists in residential-type fire testing that cannot be practically eliminated, as well as fire challenges that are expected to occur in field installations. Discussions ensued, referencing the original Los Angeles residential fire tests and the fuel load used to simulate typical living room residential fires. UL and FM ran hundreds of simulated residential fire tests. When the dust settled after two years of research, a recommendation to establish a minimum density of .05 gpm/sq. ft. for both the single and multiple sprinkler designs for residential sprinklers was accepted by UL, FM and the NFPA 13D Technical Committee. With the acceptance of the higher flow rates, changes to the fire test protocol were also made.
Are All Listings the Same?Absolutely not. Understanding the definition of terms used in the listing applications is critical to proper design and installation of residential sprinklers. Currently, the basic listing of a residential sprinkler follows the minimum .05 gpm/sq. ft. density for flat smooth horizontal (pitch not exceeding 2 units rise over 12 units run) ceilings. Any uses beyond these basic minimums require a special listing or the acceptance of the design criteria by the contractor and the Authority Having Jurisdiction (AHJ). Other than the listing protocol, the design criteria usually proposed by designers includes an increase in the minimum flow/pressure or an increase in the number of sprinklers being hydraulically calculated. At the end of the day, if the listing of the residential sprinkler does not cover the application, the designer and the AHJ become the responsible parties. Manufacturers are frequently asked about installation conditions and often render common-sense solutions subject to the approval of the AHJ. Manufacturers rarely want to become the system designer.
Fire sprinkler manufacturers have gone to great lengths to identify and qualify listings for common construction features used in residential occupancies. The greater the amount of listed applications, the less the AHJ or contractors have to become the responsible design parties. Listings follow some common terms used by most manufacturers, but many listings vary by manufacturer.
What Has the Industry Done?The fire sprinkler manufacturers have complied with the new industry standards. Understanding these new products, including their listings and applications, is critical to proper residential design and installation. Most manufacturers have abandoned the use of old residential sprinklers and listings in favor of optimizing new lines of residential sprinklers.
The following figures detail the minimum flows and pressures required for a typical new line of residential sprinklers.