Last month, this column introduced the new Emergency Communications Systems (ECS) Chapter 24 that will debut in the National Fire Protection Association (NFPA) 72-2010, the National Fire Alarm and Signaling Code. It references another new chapter, Chapter 12, Circuits and Pathways.
The new chapter uses the terms “circuits” and “pathways” interchangeably. The descriptions stem from their performance characteristics. Previously, initiating device circuit, signaling line circuit and notification appliance circuit performance class and style tables had roots in copper-wiring methods. Because fire alarm control units increasingly use communication technologies such as Ethernet, fiber optics and wireless, “pathway” has been substituted for “circuit.” Circuit tends to denote more traditional copper-wiring methods.
The code still requires the installation of all fire alarm system wiring and equipment, including all circuits controlled and powered by the fire alarm system, to comply with the requirements of NFPA 72 and NFPA 70, National Electrical Code (NEC), Article 760. And, the determination of a class designation depends on a circuit or pathway’s capability to continue to operate during abnormal conditions. Chapter 23 requires that “initiating device circuits, notification appliance circuits, and signaling line circuits shall be designated by class, depending on the circuit’s capability to continue to operate during specified fault conditions … .”
However, the code offers six pathway designations—A, B, C, D, E and X—determined by performance of the pathway during fault conditions.
Section 23.10.2 of Chapter 23 Protected Premises Fire Alarm Systems states, “Fire alarm systems used for partial evacuation and relocation shall be designed and installed such that attack by fire within an evacuation signaling zone shall not impair control and operation of the notification appliances outside the evacuation signaling zone.” This statement describes “survivability.”
Chapter 12 now contains the requirements for various levels of survivability and begins with Level 0 as a default.
Level 0 pathways have no provisions for survivability. Level 1 consists of pathways fully protected by an automatic sprinkler system complying with NFPA 13, Standard for the Installation of Sprinkler Systems, with any interconnecting conductors, cables or other physical pathways installed in metal raceways.
Level 2 pathway survivability consists of one or more of the following: two-hour fire-rated circuit integrity cable, two-hour fire-rated cable system [electrical circuit protective system(s)], two-hour fire-rated enclosure or protected area, and two-hour performance alternatives approved by the authority having jurisdiction.
Pathway survivability Level 3 includes the same as Level 2 with the additional requirement that the building has full protection by an automatic sprinkler system complying with NFPA 13, Standard for the Installation of Sprinkler Systems.
Designers, authorities having jurisdiction, and installers must design, review and install circuits common to more than one evacuation zone that also control notification appliance circuits, so a fire in one zone will not disable notification in any other zones.
MOORE, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a co-editor of the current National Fire Alarm Code Handbook. Moore is a principal with Hughes Associates Inc. at the Warwick, R.I., office.