UL Sprinkler Requirements

by George Laveric, from the 5/2002 issue of Sprinkler Age, page 21

Underwriters Laboratories, Inc. (UL) is constantly refining its test standards and documents for the fire protection industry. The following paragraphs discuss some of their recent changes.

Update on New Standard for Spray Nozzles, UL2351

In July 2000, UL adopted a new Standard for Spray Nozzles for Fire Protection Service, UL 2351. This standard covers nozzles intended for installation in accordance with the Standard for Water Spray Fixed Systems for Fire Protection Service, NFPA 15. The requirements in UL 2351 become effective on July 10, 2002.

The revisions to NFPA 15 included requirements that more clearly described the performance characteristics for fixed water spray nozzles and indicate that these nozzles are to be marked with the orifice size or discharge coefficient (K-factor). NFPA 15 also requires that the spray pattern at various pressures and orientations be verified. In regard to temperature ratings and color-coding, the requirements are the same as currently specified for automatic sprinklers.

In concert with the revised requirements of NFPA 15, UL developed a new method for measuring the discharge characteristics of fixed water spray nozzles. The criteria take into account the possibility that the nozzles could be mounted in a variety of orientations. The discharge pattern characterization of these nozzles is intended to be used by water spray system designers to specify optimal installation locations, thereby providing water coverage desired for the application. The operational test requirements for the automatic spray nozzles described in UL 2351 parallel the requirements outlined in UL 199, Standard for Automatic Sprinklers for Fire-Protection Service.

Manufacturers have been working with UL to demonstrate compliance of spray nozzles with the requirements of UL2351 and several UL Listed nozzles have already demonstrated compliance. Nozzle discharge characterization verified by UL is referenced in the manufacturer's installation instructions. Contact Mike McCormick at UL's Northbrook, Ill. facilities for further information at (847) 664-3303.

Revised Residential Sprinkler Requirements Become Effective

In January 2000, the Standard for Residential Sprinklers for Fire Protection Service, UL1626 was revised to include new requirements involving the fire test method and water flow rates that become effective July 12, 2002. The revised fire test method provides for an enhanced evaluation of the fire control effectiveness of UL Listed residential sprinklers. The modified test method considers the variability of fire challenges in the field and the level of protection required by the National Fire Protection Association Technical Committee for Residential Sprinkler Systems.

The revised fire test method incorporates a similar test configuration as the previous protocol, but references the use of new combustible materials to enhance test consistency. The fuel package for the test includes the use of polyurethane foam cushions supported vertically in a corner of the test room to create a shielded fire test scenario. Also, plywood is installed on the walls to provide for a combustible wall surface. (See Figures 1 and 2 on page 23.)

A new minimum water flow rate requirement was also specified for all residential sprinklers. A discharge density of 0.05 gpm/ft2 was established as the minimum residential sprinkler rate, after considering all available information and data including the (1) installation cost for sprinkler systems in single family dwelling units, (2) need for increased usage of residential sprinklers to save lives and property, and (3) excellent performance of these products in the field. Several manufacturers currently produce residential sprinklers that have demonstrated compliance with UL's new requirements. All UL Listed residential sprinklers produced after July 12, 2002 will be required to comply with the revised standard.

The Standards for the Installation of Sprinkler Systems in (1) One- and-Two Family Dwellings and Manufactured Homes, NFPA 13D, and (2) Residential Occupancies up to and including Four Stories in Height, NFPA 13R, are scheduled for adoption at the May 2002 NFPA World Safety Conference. Proposed revisions to these NFPA installation standards include the minimum 0.05 gpm/ft2 discharge density requirement. Sprinkler system designers should be aware of these changes in requirements when designing new sprinkler systems. Authorities Having Jurisdiction should be aware of these changes in requirements when evaluating new residential sprinkler systems installed after adoption of the revised NFPA Standards.

Sprinkler Identification Numbers (SINs)

The 1999 edition of NFPA 13 (Par. 3-2.2) requires sprinklers to be marked with Sprinkler Identification Numbers (SINs). These numbers identify the manufacturer as well as a unique model designation for every orifice size, deflector characteristic, and thermal sensitivity. Since January 2001, all UL Listed sprinklers have been identified by the SIN.

The SINs for all currently Listed sprinklers have been published in the 2002 UL Fire Protection Equipment Directory. UL's published information references the sprinkler company's name, discharge coefficient (K-factor), type of sprinkler, sprinkler response type, and the page number in the directory where further information is available.

To purchase a Fire Protection Equipment Directory, call 1-888-853-3503 or find it on the web at and click on the UL logo. This information is also available on the UL web site, You can access this information through UL's Online Certification Directory Database. Simply enter the Category Control Number (CCN) (VNWA) at the Category Control Number (CCN)/Guide Information search or enter the SIN at the keyword search.

This information was developed to assist Authorities Having Jurisdiction, fire marshals, fire inspectors, and pipe fitters/sprinkler installers in identifying the proper sprinkler when installing and maintaining sprinkler systems in accordance with the Standards for Installation of Sprinkler Systems, NFPA 13 and the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, NFPA 25.


George E. Laverick is Engineering Group Leader, Conformity Assessment Services, Fire Protection Division at UL, Northbrook. Ill. He can be reached via email at

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