2008_nec_article_760

226 Mike Holt’s Illustrated Guide to Understanding the National Electrical Code, Volume 2

AR

TIC

LE 760 Fire Alarm Systems

FPN No. 1: Fire alarm systems include fire detection and alarm notification, voice communications, guard’s tour, sprinkler waterflow, and sprinkler supervisory systems. Other circuits that might be controlled or powered by the fire alarm system include elevator capture, elevator shut-down, door release, smoke door and damper control, fire door and damper control, and fan shutdown.

NFPA 72, National Fire Alarm Code provides the require-ments for the selection, installation, performance, use, test-ing, and maintenance of fire alarm systems.

Author’s Comments:

• Buildingcontrolcircuitsassociatedwiththefirealarmsystem,such as elevator capture and fan shutdown, must complywithArticle725[760.3(E)].Article760applies if thesecom-ponentsarepoweredanddirectlycontrolledbythefirealarmsystem.

• NFPA101—Life Safety Codeorthelocalbuildingcodespeci-fieswhenandwhereafirealarmsystemisrequired.

760.2 Definitions.

Abandoned Cable. A cable that isn’t terminated to equipment and not identified for future use with a tag.

Author’s Comment: Section 760.25 requires the accessibleportionofabandonedcablestoberemoved.

Fire Alarm Circuit. The portion of the wiring system and connected equipment powered and controlled by the fire

Part I. General

760.1 Scope. Article 760 covers the installation of wiring and equipment for fire alarm systems, including all circuits controlled and powered by the fire alarm system. Figure 760–1

Author’s Comment:Residentialsmokealarmsystems, includ-ing interconnecting wiring, aren’t covered by Article 760,becausetheyaren’tpoweredbyafirealarmsystemasdefinedinNFPA72.

IntroDuctIon to artIcle 760—FIre alarm SyStemSArticle 760 covers the installation of wiring and equipment for fire alarm systems, including all circuits controlled and powered by the fire alarm system. These include fire detection and alarm notification, voice communications, guard’s tour, sprinkler waterflow, and sprinkler supervisory systems. NFPA 72, National Fire Alarm Code provides other fire alarm system requirements.

Since many people have difficulty understanding this article from the text alone, pay close attention to the illustrations as you study this material. The figures highlight important requirements and common Article 760 violations.

Figure 760–1

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 1.888.NEC.CODE (1.888.632.2633) 227

Fire Alarm Systems 760.3

Power-Limited Fire Alarm Circuit. A power-limited fire alarm circuit must have the voltage and power limited by a listed power supply that complies with 760.121 as follows: Figure 760–3

Inherently Limited (ac) [Chapter 9, Table 12(A)]

Voltage Power

0to20V 5.00xV

21Vto100V 100VA

Not Inherently Limited [Chapter 9, Table 12(A)]

Overcurrent Voltage Power Protection

0to20V 5.00xV 5A

21to100V 100VA 100/V

101to150V 100VA 1A

Author’s Comment: Inherently limited power supplies aredesignedtoburnoutifoverloaded.

760.3 other articles. Only those sections of Article 300 specifically referenced in this section apply to fire alarm cir-cuits and equipment and complies with (A) through (G) as follows.

(A) Spread of Fire or Products of Combustion. Fire alarm cir-cuits installed through fire-resistant-rated walls, partitions,

alarm system. Fire alarm circuits are classified as either non-power-limited or power-limited.

Nonpower-Limited Fire Alarm Circuit. A nonpower-limited fire alarm circuit can operate at up to 600V, and the power output isn’t limited [760.41 and 760.43]. Figure 760–2

Figure 760–3

Figure 760–2

Figure 760–4


760.21 Fire Alarm Systems

(C) Hazardous (Classified) Locations. Fire alarm cir-cuits installed in any hazardous location must be installed in accordance with Articles 500 through 516, specifically 501.150 and 502.150.

(D) Corrosive, Damp, or Wet Locations. Fire alarm circuits installed in corrosive, damp, or wet locations must be identi-fied for use in the operating environment [110.11]; must be of materials suitable for the environment in which they are to be installed [300.6]; and must be of a type suitable for the appli-cation [310.9].

(E) Building Control Circuits. Class 1, 2, and 3 circuits used for building controls (elevator capture, fan shutdown, etc.), associated with the fire alarm system, but not controlled and powered by the fire alarm system, must be installed in accor-dance with Article 725 [760.1].

(F) Optical Fiber Cables. Optical fiber cables utilized for fire alarm circuits must be installed in accordance with Article 770.

760.21 access to electrical equipment Behind Panels Designed to allow access. Access to equip-ment must not be prohibited by an accumulation of cables that prevent the removal of suspended-ceiling panels. Cables must be located so that the suspended-ceiling panels can be moved to provide access to electrical equipment.

floors, or ceilings must be firestopped to limit the possible spread of fire or products of combustion in accordance with the instructions supplied by the manufacturer for the specific type of cable and construction material (drywall, brick, etc.), as required by 300.21. Figure 760−4

(B) Ducts, Plenums, and Other Spaces Used for Environmental

Air-Handling Purposes.

Where necessary for direct action upon, or sensing of the contained air, fire alarm cables are permitted to be installed in ducts or plenums if they are installed in a metal raceway as required by 300.22(B). Figure 760–5

Exception: Plenum-rated fire alarm cables are permitted above a suspended ceiling or below a raised floor used for environmental air [760.30(B)(1) and (2), 760.154(A), and 760.179(A)].

Nonplenum-rated fire alarm cables are permitted to be installed above a suspended ceiling or below a raised floor used for environmental air, if the cable is installed in a metal raceway [300.22(C)(1)].

Figure 760–5

Figure 760–6



Author’s Comment:Racewaysandcablesarepermittedtobesupported by independent support wires attached to the sus-pendedceiling[300.11(A)and760.46].Figure 760–7

Cables run through or parallel to framing members or fur-

ring strips must be protected where they are likely to be pen-etrated by nails or screws, by installing the wiring method so

760.24 mechanical execution of Work. Equipment and cabling must be installed in a neat and workmanlike manner.

Exposed cables must be supported by the structural com-ponents of the building so that the cable will not be dam-aged by normal building use. Cables must be secured by straps, staples, hangers, cable ties, or similar fittings designed and installed in a manner that will not damage the cable. Figure 760–6

Figure 760–8

Figure 760–7

Figure 760–9

Figure 760–10



circuit conductors extend beyond a building, they must be installed in accordance with Article 800, or they must be installed in accordance with Part I of Article 300.

760.35 Fire alarm circuit requirements.

(A) Nonpower-Limited Fire Alarm Circuits. Nonpower-limited fire alarm (NPLFA) circuits must comply with Parts I and II of this article.

(B) Power-Limited Fire Alarm Circuits. Power-limited fire alarm (PLFA) circuits must comply with Parts I and III of this article.

Part III. PoWer-lImIteD FIre alarm (PlFa) cIrcuItS

760.121 Power Sources for Power-limited Fire alarm circuits.

(B) Branch Circuit. Power-limited fire alarm equipment must be supplied by an individual branch circuit that is not GFCI or AFCI protected. Figure 760–12

760.124 equipment marking. Fire alarm equipment supplying power-limited fire alarm cable circuits must be

it isn’t less than 11⁄4 in. from the nearest edge of the framing member or furring strips, or by protecting them with a 1⁄16 in. thick steel plate or equivalent [300.4(D)]. Figure 760–8

760.25 abandoned cable. To limit the spread of fire or products of combustion within a building, the accessible portion of cable that isn’t terminated at equipment and not identified for future use with a tag must be removed [760.2]. Figure 760–9

Cables identified for future use must be with a tag that can

withstand the environment involved. Figure 760–10

Author’s Comment: Cables installed in concealed racewaysaren’tconsidered“accessible,”thereforethey’renotrequiredtoberemoved.

760.30 Fire alarm circuit Identification. Fire alarm circuits must be identified at all terminal and junction loca-tions. The identification must be in such a manner that will help to prevent unintentional signals on the fire alarm system circuits during testing and servicing of other systems. Figure 760–11

Author’s Comment:Themarkingofracewaysandcablesisn’trequiredbythissection[760.124].

760.32 Fire alarm circuit cables extending Beyond a Building. Where twisted-pair power-limited fire alarm

Figure 760–11Figure 760–12



mustbeprotectedbya 1⁄16 in. thick steel plateor theequiva-lent[760.8].

Cable splices or terminations must be made in listed fittings, boxes, enclosures, fire alarm devices, or utilization equip-ment. Figure 760–13

760.136 Separation from Power conductors.

(A) General. Power-limited fire alarm conductors must not be placed in any enclosure, raceway, or cable with conductors of electric light, power, or Class 1 circuits.

(B) Separated by Barriers. Where separated by a barrier, power-limited fire alarm circuits are permitted with electric power conductors.

Author’s Comment:Separationisrequiredtopreventafireor

shockhazardthatcanoccurfromashortbetweenthefirealarmcircuitandthehigher-voltagecircuits.

(D) Associated Systems Within Enclosures. Power-limited fire alarm conductors are permitted to be mixed with elec-tric light, power, and Class 1 circuit conductors in enclosures where these other conductors are introduced solely for con-nection to the same equipment, and:

(1) A minimum of 1⁄4 in. separation is maintained from the power-limited fire alarm cable conductors.

durably marked to indicate each circuit that is a power-lim-ited fire alarm circuit.

Author’s Comment:Firealarmcircuitsmustbemarkedatallterminalandjunctionlocations[760.30].

760.130 Wiring methods on load Side of Power-limited Fire alarm Power Source.

(B) PLFA Wiring Methods and Materials. Power-limited fire alarm conductors and cables described in 760.179 must be installed as detailed in (1), (2), or (3).

(1) Exposed or Fished in Concealed Spaces. Power-limited fire alarm circuits installed exposed must be adequately sup-ported and protected against physical damage, or be installed

in a raceway.

Author’s Comment:Exposedcablesmustbesupportedbythestructural components of the building so the cable won’t bedamaged by normal building use. Cables must be secured bystraps,staples,hangers,orsimilarfittingsdesignedandinstalledinamanner thatwon’tdamage thecable.Cables run throughor parallel to framing members or furring strips must be pro-tectedwherethey’relikelytobepenetratedbynailsorscrews,byinstallingthewiringmethodsoitisn’tlessthan11⁄4in.fromthenearestedgeof the framingmemberor furringstrips,or it

Figure 760–13

Figure 760–14



cable, cable tray, or raceway with power-limited fire alarm conductors or cables.

Author’s Comment: The concern is that a fault from audioamplifiercircuitstofirealarmcircuitshasthepotentialtocreatea hazard by disrupting the operation of fire alarm systems.However,thisnewrestrictiondoesn’tapplytothevoiceannun-ciationaudiocircuitssuppliedandcontrolled froma firealarm

(G) Other Applications. Power-limited fire alarm circuit con-ductors must be separated by not less than 2 in. from insu-lated conductors of electric light, power, or Class 1 circuits unless:

(1) All of the electric light, power, and Class 1 circuit con-ductors, or all of the power-limited fire alarm circuit conductors, are in a raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, or underground feeder cables. Figure 760–14

760.139 Power-limited Fire alarm circuits, class 2, class 3, and communications circuits.

(A) Two or More Circuits. Power-limited fire alarm circuits, communications circuits, or Class 3 circuits are permitted to be in the same cable, enclosure, cable tray, or raceway. Figure 760–15

(B) PLFA and Class 2 Circuits. Class 2 circuits are permitted to be within the same cable, enclosure, cable tray, or raceway as conductors of power-limited fire alarm circuits provided the Class 2 circuit conductor insulation isn’t less than that required for the power-limited fire alarm circuit.

Author’s Comment:ListedClass2cableshaveavoltageratingof 150V [725.179(G)], whereas listed power-limited fire alarmcableshaveavoltageratingof300V[760.179(C)].

(D) Audio System Circuits and Power-Limited Fire Alarm Circuits. Audio system circuits [640.9(C)] using Class 2 or Class 3 wiring methods must not be installed in the same

Figure 760–15

Figure 760–16

Figure 760–17



Author’s Comment: Power-limited fire alarm cables identifiedassuitable forplenumor riserusearenot required inone-ortwo-familydwellings.

(C) Other Wiring Within Buildings.

(1) General. Type FPL cable is permitted.

(2) In Raceways. Cables are permitted to be installed in raceways.

(3) Nonconcealed Spaces. Chapter 3 cables meeting the requirements of 760.179(A) and 760.179(B) can be installed in noncon cealed spaces where the exposed length of cable doesn’t exceed 10 ft.

(D) Cable Substitutions. Power-limited fire alarm circuit cables are permitted to be substituted in accordance with Table 760.154.

Part IV. lIStInG requIrementS760.179 listing and marking requirements of Power-limited Fire alarm cables (PlFa). Power-lim-ited fire alarm cable installed within buildings must be listed in accordance with (A) through (H) and must be marked in accordance with (I).

Power-limited fire alarm cable used in a wet location must be listed for use in wet locations or have a moisture-impervious metal sheath. Figure 760–18

panel and commonly required in high-rise buildings and simi-larapplications.

760.143 Support. Power-limited fire alarm cables are not permitted to be strapped, taped, or attached to the exterior of any raceway as a means of support. Figure 760–16

760.154 applications of Power-limited Fire alarm cables (PlFa).

(A) Ducts, Plenums, and Other Space Used for Environ mental Air. Where necessary for direct action upon, or sensing of the contained air, power-limited fire alarm cables are permit-ted to be installed in ducts or plenums if installed in a metal raceway [300.22(B)]. Power-limited fire alarm cables identi-fied as suitable for plenum use can be installed above a sus-pended ceiling or below a raised floor used for environmental air. Figure 760–17

Author’s Comments:

• Power-limited firealarmcablesnot identifiedas suitable forplenum use can be installed above a suspended ceiling orbelowaraisedfloorusedforenvironmentalair,butonlyifthepower-limited fire alarmcablesnot identified as suitable forplenumuseareinstalledinametalraceway[300.22(C)(1)].

• Firealarmcablesinstalledbeneatharaisedfloorinaninfor-mation technology equipment room (computer room) aren’trequiredtobeplenum-rated[300.22(D)and645.5(D)(6)(c)].

(B) Riser.

(1) Power-limited fire alarm cables installed in vertical runs penetrating more than one floor must be riser-rated Types FPLR or FPLP [760.179(E)]. Listed riser raceways and listed plenum signaling raceways are permitted to be installed in vertical riser runs, but only if the cables con-tained in these raceways are riser- or plenum-rated Types CL2R, CL3R, CL2P, or CL3P.

(2) Power-limited fire alarm cables installed in vertical runs penetrating more than one floor aren’t required to be riser-rated if installed within a metal raceway.

Author’s Comment: Metal raceways containing circuit con-ductors from a power-supply system that operates below 50Vgenerally aren’t required to be connected to an equipmentgroundingconductor[250.86and250.112(I)].

(3) FPL cable is permitted for all applications in one- and two-family dwellings.

Figure 760–18



(A) Conductor Materials. Conductors must be solid or stranded copper.

(B) Conductor Size. The size of conductors in a multicon-ductor cable must not be smaller than 26 AWG. Single con-ductors must not be smaller than 18 AWG.

(C) Cable Voltage Rating. Power-limited fire alarm cable must have a voltage rating of 300V and this rating must not be marked on the cable [760.179(I)].

(D) Type FPLP. Power-limited fire alarm plenum cables (FPLP) are listed for use in ducts, plenums, and other envi-ronmental air spaces [760.154(A)]. Figure 760–19

Author’s Comment: Cables identified as suitable for plenumusecanbe installed in environmental air spaces, but theyarenotpermittedtobeinstalledinductsorplenums!See760.3(B)inthistextbookfordetails.

(E) Type FPLR. Power-limited fire alarm riser cables (FPLR) are listed for use in a vertical run in a shaft, or from floor to floor [760.154(B)].

(F) Type FPL. Power-limited fire alarm cables (FPL) are listed for general-purpose use [760.154(C)].

(H) Coaxial Cables. Coaxial cables are listed as FPLP, FPLR, or FPL.

(I) Cable Marking. The 300V rating of power-limited fire alarm cable must not be marked on the cable [760.176(C)].

FPN: Voltage markings on cables may suggest that the cables are suitable for Class 1, or electrical power applica-tions, which they’re not.

Figure 760–19


Practice Questions Article 760

AR

TIC

LE

760 Practice Questions5. Cable splices or terminations in power-limited fire alarm

systems shall be made in listed _____ or utilization equipment.

(a) fittings(b) boxes or enclosures(c) fire alarm devices(d) all of these

6. Audio system circuits using Class 2 or Class 3 wiring methods shall not be installed in the same cable or raceway with _____.

(a) other audio system circuits(b) power-limited fire alarm conductors or cables(c) a or b(d) none of these

7. Power-limited fire alarm cables installed within buildings shall be _____ as being resistant to the spread of fire.

(a) marked FR(b) listed(c) identified(d) color-coded

artIcle 760—FIre alarm SyStemS—PractIce queStIonS1. Fire alarm cables that are not terminated at equipment

and not identified for future use with a tag are consid-ered abandoned.

(a) True(b) False

2. Fire alarm cables identified for future use shall be marked with a tag of sufficient durability to withstand _____.

(a) moisture(b) humidity(c) the environment involved(d) none of these

3. The power source for a nonpower-limited fire alarm circuit shall not be supplied through a(n) _____.

(a) ground-fault circuit interrupter(b) arc-fault circuit interrupter(c) inverse time circuit breaker(d) a or b

4. The number of nonpower-limited fire alarm conductors in a raceway shall not be required to comply with the fill requirements contained in 300.17.

(a) True(b) False

2008_nec_article_760

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