TO: Design Professionals and Authorities Having Jurisdiction
DATE: June 26, 2002
SUBJECT: Changes in Minimum Flow Rates for Residential Sprinklers
We are writing to advise you of an important change that will take place on July 12, 2002 with regard to minimum flow rates associated with listed residential sprinklers for use in accordance with NFPA 13D and NFPA 13R. July 12th is the effective date for the implementation of new listing criteria for these sprinklers by Underwriters Laboratories, Inc. (UL). UL announced the pending change 18 months ago, and in recent months the subject has attracted much attention due to the proposed parallel change within the NFPA standards. The purpose of this letter is to clarify the nature of the change and how it is to be implemented.
1. What has changed? Effective July 12, 2002, new UL listings will be in effect for residential sprinklers used in accordance with NFPA 13D and NFPA 13R. Since virtually all residential sprinkler listings are promulgated by UL, this affects all residential sprinkler models.
2. What editions of NFPA 13D and NFPA 13R are affected? All of them. This is because the NFPA standards allow maximum spacing and minimum flow criteria for residential sprinklers based on the listing of the sprinklers. When the sprinkler listings change July 12th, the available selections are immediately changed.
3. How will this affect jobs in progress? Systems for which plans are approved on or before July 12th should definitely be permitted to proceed to installation. Those plans were approved on the basis that listed sprinklers were available for those spacings and flows, and it is expected that the sprinkler manufacturers will have sufficient supplies of those sprinklers to meet the demand. The listings of those sprinklers are not revoked in any way, but sprinkler manufacturers will not be able to produce new sprinklers in accordance with the former listings. Authorities having jurisdiction are asked to be reasonable with regard to jobs for which plan approvals are pending at the time of the July 12th changeover.
4. How do the new listings differ from the old listings? The new listings are those associated with a revision of the fire test applied to residential sprinklers in the UL 1626 product standard, and with two other changes announced by UL. The first is that the listings will reflect a minimum average floor density of 0.05 gpm/ft2, and the second is that all sprinklers in the design area will be required to meet the same minimum flow and pressure criteria. In other words, there will be no reduced flow rate for the second sprinkler in a 13D system, or for the second, third and fourth sprinklers in a 13R system.
5. Are the manufacturers providing new models of sprinklers or simply using the old models at new flow rates? Depending on the manufacturer and model, it could be either case, but in all cases the sprinklers have been listed on the basis of the revised fire test. It is possible that some models of sprinklers will have passed the new fire test at the same flow rate as previously listed. For example, there were never any sidewall sprinklers listed with minimum average floor densities of less than 0.05 gpm/ft2 .
6. Is it safe to assume that all existing models of sprinklers can be used by simply ensuring a minimum average floor density of 0.05 gpm/ft2 ? No. It is important to recognize that the 0.05 gpm/ft2 average floor density is a minimum, but the flow rate of any particular sprinkler model will be based on its performance in the revised fire test. Some models will require minimum flow rates that result in an average floor density exceeding 0.05 gpm/ft2 .
7. How do we find out what the new UL listings are? The new listing information is available from the individual sprinkler manufacturers, and will also be available on the UL website www.ul.com. On the UL homepage under the “Services” options select “Online Certifications Directory”. Choose “UL Category Code / Guide Information” and search under the category “VKKW” for residential sprinklers. Information contributed by the sprinkler manufacturers will also be available at www.NFSA.org beginning July 1, 2002.
8. Why did UL make these changes? At the beginning of 1999, it was found that the fire test used to qualify residential sprinkler designs at UL allowed too much variability. This led to a cooperative effort between UL, the sprinkler manufacturers, and Factory Mutual Research Corporation, which had performed the original research that led to the development of the residential sprinkler in the late 1970s. The 18-month effort was aimed at redesigning the fire test to make it more repeatable. As part of this effort, the fire test was “recalibrated” against the corner furniture scenario that was used as the “reasonable worst case” fire scenario when the residential sprinklers were first developed. The severity of the fire scenario effectively determines the level of risk to accept with the performance of the sprinklers, and the NFPA Technical Committee on Residential Sprinkler Systems that has charge of NFPA 13D and NFPA 13R was recognized as the consensus group that makes this decision through the choice of the fire scenario. In completing the development of the new fire test, both laboratories concluded that an average floor density of 0.05 gpm/ft2 should be established as an absolute minimum in order to ensure that residential sprinklers will be capable of fire control within dwellings even under the “reasonable worst case” scenario.
The loss of the reduced secondary flow rates is a UL policy decision based on the fact that the current fire test does not necessarily check the effectiveness of the reduced water application rates.
9. Will the new listings add cost to NFPA 13D and 13R systems? Unfortunately, in some cases the answer is “yes” compared with recent listings, but not compared to the original residential sprinkler listings. Higher flow rates and the loss of the reduced secondary flow rates result in higher water demands, which in turn can result in additional cost through larger pipe sizes as well as the potential for charges associated with larger water meters and other equipment. However, it should be noted that the minimum flow rates will still be substantially lower than those available when residential sprinklers were first introduced to NFPA 13D in 1980. The original criteria of 18 gpm for a sprinkler covering a maximum of 144 ft2 equates to a minimum average floor density of 0.125 gpm/ft2, and the two-sprinkler minimum flow of 26 gpm over 288 ft2 amounted to an average floor density of 0.09 gpm/ft2, almost twice as high as the new minimums.
10. Do the sprinkler manufacturers support the changes in UL listings? Yes, the sprinkler manufacturers agree that the changes were appropriate at this time to ensure that residential sprinklers maintain the level of performance expected by the NFPA 13D and 13R standards.
11. Is there any possibility of lower water application rates in the future? The sprinkler industry has not closed the door to lower water application rates, since they recognize that reduced water supply demands can help make residential sprinkler systems more affordable, and result in more homes being sprinklered. The industry will continue to work with the product listing laboratories and the NFPA Technical Committee on Residential Sprinkler Systems in an attempt to make residential sprinklers even more cost-effective than they are at present, while not sacrificing the confidence that residential sprinklers will perform when needed to help save lives.
12. Where do I go if I have additional questions? Questions with regard to a specific model of sprinkler should be addressed to the sprinkler manufacturer. General questions about the changes are welcomed by the National Fire Sprinkler Association, which includes representation for the fire sprinkler manufacturers among its broad obligations to the fire sprinkler industry. Send questions to residentialsprinklers@nfsa.org. The questions and answers listed above are being posted on the Association’s website at www.nfsa.org and will be expanded as additional questions come in.
Very truly yours,
Russell P. Fleming, P.E.
Executive Vice President