Topic: Fire Protection Systems


Understanding hydraulic requirements in NFPA 13D

A common question we receive through NFPA's technical advisory services for NFPA 13D, Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes, involves the hydraulic calculation of the system. Unlike NFPA 13, Installation of Sprinkler Systems, NFPA 13D does not require full-blown hydraulic calculations that assess friction loss of every fitting and linear foot of pipe. One of the goals of the NFPA 13D technical committee is to promote the inclusion of systems in both new construction and retrofit installations. As such, requiring a complicated and time-consuming hydraulic calculation procedure would add cost to the project and in some cases may preclude otherwise qualified designers from being engaged with the standard. NFPA 13D offers two simple approaches to these calculations. These procedures are described in both an eight-step and 12-step process that require limited mathematical computation, while still providing the assurance that there will be sufficient flow and pressure for the particular system being installed. These calculations are conservative, but are simple to execute and not time-consuming. The time savings can be seen both on the design side and on the plan review side. Reviewing the hydraulics for a 13D system for a municipal plan reviewer is a simpler endeavor than that of the NFPA 13 approach. Matt Klaus is NFPA's principal fire protection engineer and staff liaison for NFPA 13D. Klaus is a regular contributor to this blog and discusses the technical components of home fire sprinklers. 

The facts on NFPA 13D and water mist systems

"Can I use a water mist system instead of automatic sprinklers?" That was a common question posed during the development of the 2013 edition of NFPA 13D, Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes. The NFPA 13D Residential Sprinkler Systems Technical Committee concluded that the answer lies somewhere other than this document. The NFPA 13D committee does not have the scope to write requirements for water mist systems; they provide design and installation criteria for automatic sprinklers in residential settings. If an applicable building code requires sprinkler system installation in accordance with NFPA 13D, it must pertain to automatic sprinkler systems. The 2013 edition of the standard does include a statement in Chapter One noting that water mist systems differ from sprinkler systems. If you are looking for guidance on water mist systems, please refer to NFPA 750, Water Mist Fire Protection Systems. However, that's not to say that water mist systems are not appropriate or should not be used in residential settings. Water mist systems are a great option for many applications, one of which may be single-family homes. In this instance, the issue is about document scope and scoping criteria, not about one suppression technology being better than another. Matt Klaus is NFPA's principal fire protection engineer and staff liaison for NFPA 13D. Klaus is a regular contributor to this blog and discusses the technical components of home fire sprinklers. 

Home fire sprinklers requirements in California yield no negative impact on construction

The Modesto Bee reports that home building permits were up nearly 55% in the Sacramento area of California this year compared to the same period last year. The article explains that the Sacramento results mirror a statewide increase in building permits for single family homes; proving that fire sprinkler requirements do not thwart home building. California is one of two states that adopted fire sprinkler requirements in all new one- and two-family homes, effective January 1, 2011.  Maryland also adopted the requirement statewide. In other states, opponents of home fire sprinkler requirements – which are included in all national model codes representing minimum standards to achieve a reasonable level of safety – have lobbied extensively against the requirement on the claim that adoption of fire sprinklers in new home construction will negatively impact home building. This claim is refuted by a study by the Fire Protection Research Foundation that found there is no negative impact in housing supply or cost in communities adopting the requirement, as compared to communities without the requirement. The National Association of Homebuilders (NAHB) website contains permit data showing an overall average increase of 26% in single family home permits in the U.S., while California has experienced a 51% increase in permits issued for the same period. In contrast, South Carolina - included among the states rejecting statewide adoption of one- and two-family home fire sprinkler requirements - has experienced a 24% increase in permits; below the national average. View home fire sprinkler legislation/adoption updates by states and local communities.

NFPA 13D fire sprinkler systems on well water

Well systems incorporating fire sprinklers at the start of the building process are set up to effectively address this fire protection application. The following will explain how NFPA 13D systems are integrated into well systems.Water sits in three areas in a well-fed system: in the well above the pump, refilling into the well as it is used, and in the holding tank in the home. NFPA 13D states that the refill rate can be counted on to help supply part of the demand, and therefore, the duration demand of 7 or 10 minutes can be met by the sum of these three sources. The refill rate can be determined by the person that drills the well.Wells are set up at the inception of the home building process and a larger well pump is usually installed along with larger expansion tanks. Homes on well water most likely will need a pump to serve the domestic water supply. The cost associated with providing additional pressure to run the fire sprinkler system may simply be the difference between the regular pump the homeowner must install to obtain the necessary pressure for domestic use, and a higher flow pump, or a booster pump and tank. Residential pump and tank manufacturers tell us that the expansion tanks are sized to pick up the difference between the well capacity and demand so they are not necessarily as large as some would believe. To meet the requirements of NFPA 13D, many installations have been done using this method, effectively and cost competitively.According to NFPA 13D, where a pressure tank is used for the water supply those who meet the requirement of ASME Boiler and Pressure Vessel Code are acceptable, provided the authority having jurisdiction considers the air or nitrogen supply reliable.Stand alone tank systems are similar to the pressurized tank systems in that they can be set up to provide for the difference in supply as opposed to total demand. According to manufacturers, generally for little extra cost, total demand can be covered. They say that stagnation is easily addressed during testing, and that no problems have been identified. They advise that a separate pump is required but is also for relatively low cost and highly competitive. It has the benefit of not being used for anything but the fire demand, so the system is never compromised.Stand-by power is not required by code, but many manufacturers build their systems with battery back-up as a standard feature. They posit that frequent maintenance is not required on these systems. It consists of periodic checks that are neither difficult nor time consuming.According to General Air Products, one of the manufacturers consulted in order to address this technical issue, they “sell systems every day to meet the varying demands of the marketplace. Every situation is not the same but we have yet to find a scenario which cannot be addressed technically or cost effectively.”
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