National Electrical Code Requirements for Security/Fire-Alarm Ssytems

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NATIONAL ELECTRICAL CODE REQUIREMENTS  FOR  SECURITY/ FIRE-ALARM SYSTEMS Because of the potential fire and explosion hazards caused  by  the  improper  handling  and  installation  of electrical  wiring.  certain  rules  in  the  selection  of materials  and  quality  of  workmanship  must  be followed  as  well  as  precautions  for  safety,.  The National Electrical Code® (NEC®) was developed to standardize and simplify these rules and provide some reliable  guide  for  electrical  construction. The  NEC®  is  published  (and  frequently  revised) by the National Fire Protection Association (NFPA), Batterymarch  Park.  Quincy,  MA  02269.  It  contains specific rules and regulations intended to help in the practical  safeguarding  of  persons  and  property  from hazards arising from the use of electricity,, including low voltage. used in the majority of security/fire-alarm systems. Article  725  of  the  NEC®  covers  remote-control. signaling,  and  power-limited  circuits  that  are  not  an integral part of a device or appliance. The  NEC® (section 725-1) states: The circuits described herein (Article 725) are characterized  by  usage  and  electrical  power limitations  that  differentiate  them  from  light and  power  circuits  and.  therefore.  special consideration is given with regard to minimum wire   sizes,   derating   factors,   overcurrent protection,    and  conductor  insulation requirements. Personnel  assigned  to  install  security/fire-alarm systems  should  become  familiar  with  Article  725  of the NEC® as well as Article 760, “Fire Protective Signaling   Systems.” This   article   covers   the installation   of   wiring   and   equipment   of   fire- protective signaling systems operating at 600 volts or less. Other NEC® articles of interest to security/fire- alarm  installers  include  the  following: 1. Section 300-21, ‘Spread of Fire or Products of Combustion.” 2. Articles 500 through 516 and Article 517, Part G (dealing with installations in hazardous locations). 3.  Article  110,   “Requirements  for  Electrical Installations” and Article 300. “Wiring Methods.” 4. Article 310. -“Conductors for General Wiring.” 5.  Fire-protectile  signaling  circuits  and equipment will be grounded according to Article 250, except  for  dc-power  limited  fire-protective  signaling circuits that have a maximum current of 0.03 amperes. 6. The power supply of nonpower-limited fire- protective signaling circuits will comply with chapters 1 through 4 and the output voltage will not be more than 600 volts, nominal. 7. Conductors of No. 18 and No. 16 sizes will be permitted to be used provided they, supply loads that do not exceed the ampacities given in table 402-5 and are installed in a raceway or a cable approved for the purpose. Conductors larger than No. 16 will not supply loads  greater  than  the  ampacities  given  in  tables  310-16 through 310-19. 8. When only nonpower-limited fire-protective signaling circuits and Class 1 circuits are in a raceway, the number of conductors will be determined according to section 300-17. The derating factors given in Note 9 to tables 310-16 through 310-19 will apply if such conductors carry continuous loads. 9.  Where  power-supply  conductors  and  fire- protective signaling circuit conductors are permitted in a raceway according to section 760-15, the number of conductors  will  be  determined  according  to  section 300-17. The derating factors given in Note 8 to tables 310-16 through 310-19 will apply as follows: a.  For  all  conductors  when  the  fire- protective  signaling  circuit  conductors  carry continuous loads and the total number of conductors is more than three. b.   For  the  power-supply  conductors  only  when the  fire-protective  signaling  circuit  conductors  do  not carry  continuous  loads  and  the  number  of  power-supply conductors is more than three. 10.  When  fire-protective  signaling  circuit conductors  are  installed  in  cable  trays.  comply  with sections 318-8 through 318-10. UNDERSTANDING  BASIC INSTALLATION  OF  SECURITY/ FIRE-ALARM  SYSTEMS The installation of a protective security/fire-alarm circuit should always start at the protective-circuit energy source, as if it were an end-of-line battery-a battery. remote from the control panel-even though it may actually be a power supply installed in the panel. A pair of wires is run from this power source to the first contact location, but just the positive wire is cut and 8-2

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