Ken Wagoner, SET - Center for Life Safety Education · 2007-04-04 · Ken Wagoner, SET All NFPA-13 References are from the 2002 ... sprinkler spacing for light hazard ... IN NFPA-13D

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Ten Common System DesignMistakes & How to Avoid Them

SpeakerKen Wagoner, SET

All NFPA-13 References are from the 2002Edition. Similar wording is contained in the 1999 edition,

however the paragraph numbering is not identical

All emphasis is by the presenter, and not contained inthe original text of NFPA-13

Presented February 28, 2007

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SpeakerKen Wagoner, SET

Kenneth W. Wagoner, SET, a 1977 graduate ofBethany College (KS), owns and operatesParsley Consulting Engineers, Escondido,California. He holds NICET certifications inSprinkler System Layout, Fire Alarms,Inspection & Testing, and Special Hazards, andis an NFPA Certified Fire Plan Examiner. He isa member of AFSA, UFCA, NFPA, and the SanDiego Fire Protection Assn.

10 Common System DesignMistakes & How to Avoid Them

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Common Mistake #1 NO ROOF SLOPE INFORMATION ON PLANS

NFPA-13, Section 11.2.3.2.4establishes that for sloped ceilings inNON-STORAGE applications that thesystem area of operation shall beincreased by 30 percent withoutrevising the density when spraysprinklers, including extendedcoverage sprinklers (per 8.4.3.4), largedrop, and quick response sprinklers areused on sloped ceilings with a pitchexceeding one in six (a rise of two unitsin a run of 12 units, a roof slope of 16.7percent) in non-storage applications

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NFPA-13, Sections 8.4.3, and 8.4.6.1limit the use of ESFR sprinklers tobuildings or areas with roof or ceilingslopes not exceeding 2 in 12

NFPA-13, Section 12.1.7 cautions thatthe criteria in chapter 12 relating toprotection of storage is intended toapply only to buildings with ceilingslopes not exceeding 2 in 12

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NFPA-13, Sections 12.4.1 advisesthat the criteria in section 12.4covering tire storage is limited tobuildings or areas with roof or ceilingslopes not exceeding 2 in 12

Sprinkler listing criteria may limit ormodify sprinkler operatingcharacteristics relative to slope ofroof/ceiling

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Partialcatalogdata sheetfrom Tyco-Fire, CC2sprinkler,showinglimits ofceilingslope

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Partialcatalogdata sheetfrom Tyco-Fire, LF-IIresidentialsprinkler(TY2234),showingrevisionstominimumflow/pressure relativeto ceilingslope

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Full height cross section on plans (asrequired by NFPA-13, 14.1.3 (4),should include information detailingroof slope, and be verified

Hydraulic calculation cover sheetshould include line item to indicateroof slope was checked indetermining remote area andapplicability of density

Catalog data sheets for automaticsprinklers should have roof or ceilingslope information highlighted


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Common Mistake #2IDENTIFICATION OF CONSTRUCTION TYPE

NFPA-13, Sections 3.7.1 & 3.7.2 definethe types of construction, broken into twocategories – obstructed & unobstructed.

Annex notes for 3.7.1 establish criteriafor seven examples of obstructedconstruction

Annex notes for 3.7.1 establish criteriafor five examples of unobstructedconstruction

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Table 8.6.2.2.1(a) establishes maximumsprinkler spacing for light hazardoccupancies based in part on thedesignation of the type of construction,when using standard spray sprinklers.

Table 8.8.2.1.2 establishes maximsprinkler spacing for extendedcoverage sprinklers in all occupancyclasses based in part of the designationof the type of construction

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Table 8.11.2.2.1 establishes maximumsprinkler spacing for large dropsprinklers in all occupancies based inpart on the designation of the type ofconstruction

Table 8.12.2.2.1 establishes maximumsprinkler spacing for ESFR sprinklers inall occupancies based in part on thedesignation of the type of construction

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Sections 8.6.4.1.1 and 8.6.4.1.2establish minimum and maximumdeflector positions based on thedesignation of type of construction,using standard upright and pendentspray sprinklers

Section 8.8.4.1.1 and 8.8.4.1.2establish minimum and maximumdeflector positions based on thedesignation of type of construction,using extended coverage upright andpendent spray sprinklers

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Sections 8.11.4.1.1 and 8.11.4.1.2establish minimum and maximumdeflector positions based on thedesignation of type of construction,using large drop sprinklers

Section 8.12.4.1.5 establishes thelocation of sprinklers and branch linesin obstructed construction using ESFRsprinklers

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Do not allow construction typestatement without detailed informationon parameters of framing type:

EXAMPLE: Roof (deck) framingconsists of open wood trusses, with2x6 top chord, 2x6 bottom chord, 2x4web member. Framing spaced 3’-0”on center, and framed into 30” deepGlu-Lam beams. Construction isclassed as unobstructed (wood truss)per NFPA-13, A-1-4.6 (unobstructeddefinition e).


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NFPA-13, Section 14.1.3(4) requiresa full height cross section withstructural member information ifrequired for clarity.

Careful review of construction typeshould be madeprior to designprior to release of plans for reviewprior to stocklistingprior to installation.


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Common Mistake #3BOILER PLATE DETAILS & NOTES

With the growth of CAD, and theability to import text into a drawing,many general notes and details aregeneric in nature and do notaccurately reflect the conditions of theproject

Errors in stocklisting, hydrauliccalculations, pipe fabrication,installation and testing can result fromfailure to review general notes.

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Common Mistake #3

Every general note should bereviewed prior to issuance of plans foraccuracy and relevance to project:

EXAMPLE: “Roof (deck) framingconsists of 2x12 solid wood members,30” center-to-center, spanning up to18’-0”, framed into 35 3/8” glu-lambeams. Construction is classed asobstructed (wood joist), per NFPA-13,A-1-4.6 (obstructed type e).”Note clearly indicates conditions, and provides

information for verification of designations

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Common Mistake #3

Every general note should bereviewed prior to issuance of plans forlack of clarity of information provided:

EXAMPLE: “Branch line piping to beASTM A795 Schedule 40, Dyna-Thread, or Schedule 10 pipe, withthreaded, welded or grooved fittings.”Not possible to verify pipe or fittings

used in calculations as there is no cleardefinition of which type of pipe is to beused for branch lines

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Common Mistake #3

Every general note should bereviewed prior to issuance of plans forlack of clarity of information provided:

EXAMPLE: “System designed inaccordance with requirements for[light] [ordinary group 1] [ordinarygroup 2] [rack storage] [generalstorage]”Generic note with options was not

edited to pick applicable design criteriaprior to plans being issued.

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Common Mistake #4INCORRECT LOSS THROUGH METER

IN NFPA-13D SYSTEMS

Hydraulic calculations for single familyresidence fire sprinkler systems arerequired to take into account the frictionloss for the flow through the watermeter.

NFPA-13D, Section 8.4.4(4) requiresdesigner to review actual meter loss,for possible use in calculations

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IN NFPA-13D SYSTEMS

If actual loss from manufacturer isworse than those values in Table8.4.4(g), that value must be used in thecalculations.

If the actual loss from the manufactureris less it MAY be used instead of thevalue from the table, per NFPA-13D,8.4.4(4)

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IN NFPA-13D SYSTEMS

∆ = Less than 1 psi

‡= Above Max rated flow of commonly available meters

3710‡‡52

246‡‡39

124132631

∆2391826

∆1381423

∆∆24918

PSIPSIPSIPSIPSIGPM↓2"1½"1"¾"⅝"Size→

Water Meter Loss Figures from NFPA-13D Table 8.4.4(g)

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IN NFPA-13D SYSTEMS

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Equivalent lengths for check valvesin various sizes shown in NFPA-13,Table 14.4.3.1.1 are not always inagreement with manufacturer’s datasheets.

Equivalent lengths or specificpressure losses through valvesshown on manufacturer’s datasheets should be used.

Common Mistake #5INCORRECT LOSS THROUGH VARIOUS TYPES OF VALVES

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EXAMPLE – 6” swing check valve isshown in NFPA-13 as beingequivalent to 32’ of schedule 40 pipe

Friction loss per foot (Pe) for 6”schedule 40 pipe, with 400 gpmflowing is 0.00646 psi

32’ x 0.00646 = 0.206 psi


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Sampleloss chartfor TYCOCV-1FRRiserCheckValve

Loss forsimilar flow(400gpm)is 0.35 psi,and whensafetyfactor of15% isadded,0.40 psi

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EXAMPLE – 2½” butterfly valve isshown in NFPA-13 as being equivalentto 7’ of schedule 40 pipe

2 ½” gate valve is shown in NFPA-13as being equivalent to 1’ of schedule40 pipe

Identification of butterfly valve as “gatevalve” can reduce loss to frictionthrough fitting by 85%


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Common Mistake #6NO ELEVATION CHANGE FROMTEST POINT TO BASE OF RISER

Location of test hydrant is required byNFPA-13, 14.1.3 item 10, to beindicated on plans, and included in thatinformation is the elevation of thesystem relative to the test hydrant.

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Common Mistake #7NO EVIDENCE OF PEAKING FOR GRID

NFPA-13, 14.4.4.2 requires thedesigner to provide additionalcalculations on either side of theremote area in gridded systems toprove that the area calculated isindeed the most demanding remotearea used.

Computer programs which show thepeaking shall be acceptable using asingle set of calculations

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Flow plot diagram, as required by NFPA-13, Section 14.3.3(item 15), should also give some indication of peaking. Abovesample shows remote area roughly centered between primaryand secondary cross mains

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Common Mistake #8GENERIC HANGER DETAILS NOT TO SCALE

Sketch 1 does not show actual scale relationshipbetween framing member and lag screw

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Sketch 2 shows relationship to width, height offraming member, and lag screw length. As ageneral rule, the fewer threads engaged in wood,the lower the capacity of the fastener.

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Lag screws, sometimes called lag bolts, have ahex head, gimlet or cone point and a thin, sharp,coarse pitched thread. They are designed forinsertion into wood and produce their own matingthread. Threading is usually 60% to 67% of thelength

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Common Mistake #9REMOTE AREA NOT PER NFPA-13

NFPA-13, Fig 14.4.4.1.1.1 provides thatthe minimum length of the remote areaparallel to the branch lines is to beequivalent to at least 1.2 x √Remote Area

As spacing of sprinklers along branch linesmay not be uniform, review of actual widthis advisable. Procedure shown in A.14.4.4.not always accurate if sprinkler spacing isnot completely uniform along branch line

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Maximum spacing of 15’ betweenbranches, 8’-0” between sprinklers =120 square feet per sprinkler

1,500 square feet ÷ 120 = 12.5, or 13sprinklers flowing in remote area

1.2 x √1500 = 46.47’ (±46’-5¾) ÷ 8’-0”spacing = 5.80, or 6 sprinklers

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Sprinklerspacing is not aconsistent 120square feet foreach sprinkler,therefore thequantity of 13sprinklersflowing is notenough toachieve at least1,500 squarefeet of remotearea.

In the example,it takes 18sprinklers tocover at least1,500 squarefeet

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Sprinklerspacing alongbranch lines isnot consistent,therefore thenumber ofsprinklerscalculation doesnot result in aremote areawide enough tosatisfy therequirement for1.2 x √ RemoteArea

Six sprinklersalong branchlines result in awidth of only42’-11”

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Common Mistake #10LATERAL RESTRAINT MISSING

NFPA-13, 9.3.6.3 requires end sprinkler on abranch line to be restrained againstexcessive vertical and lateral movement

NFPA-13, 9.3.6.4 requires restraint atinvervals not exceeding 30’ along branchlines, if vertical or lateral movement wouldresult in impact against building structure,equipment, or finish materials

“Short Rodding” or use of Tolco Fig 25,AFCON Fig 310 or other similar fittingprovides restraint in vertical direction ONLY.

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Anexampleof onemethodtoprovidelateralrestraintforbranchlines

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Anexampleof onemethod toprovidelateralANDverticalrestraintfor branchlines

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Ken Wagoner, SET

Parsley Consulting350 West 9th Avenue, Suite 206

Escondido, CA 92025-5053Ph: 760-745-6181Fax: 760-745-0537

[email protected]

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Ken Wagoner, SET - Center for Life Safety Education · 2007-04-04 · Ken Wagoner, SET All NFPA-13 References are from the 2002 ... sprinkler spacing for light hazard ... IN NFPA-13D