Fire alarm systems are rapidly evolving as today’s buildings are designed with high-tech intelligent interactive systems operating the building’s infrastructure. For decades, the role of a fire alarm system was to simply evacuate a building and notify first responders. But as technology becomes more advanced, the growing need for coordination of building systems is driving a change, and traditional building codes are responding as well.
To understand the governing codes of fire alarms, a distinction must be made between the types of fire alarms, the differences in notifications, and the complexity of the electrical components.
In general terms, the main components of a fire alarm system are detectors. The detectors are connected to a central fire panel through cables that alert local emergency responders when an alarm is activated. The alarm can be activated manually, automatically through smoke/heat detection, or activation of other fire-related systems i.e. sprinklers systems.
Types of fire alarm systems
Within commercial buildings, there are basically two types of fire alarm systems: conventional and addressable. The primary goal of any fire alarm system is to evacuate the premises, prevent loss, and increase safety, but there are reasons why one might be used over the other.
Conventional Fire Alarms Systems: Conventional alarm systems are the most traditional and widely used. They are well-proven solutions for fire protection. This type of system is often more suitable as a viable fire notification for singular installations rather than large campus type facilities since the general location of a hazard is identified in a “zone,” rather than a pinpointed location.
Addressable Fire Alarm Systems: Addressable fire alarm systems offer more efficient incident identification, flexibility, and intelligence. For addressable fire alarms, each device is connected to the main fire control center with a unique identifier that can specifically identify the detector that caused the alarm. Because of its ability to pinpoint specific locations quickly, this type of installation often works best in large commercial/industrial multi-building facilities which can direct the fire-fighting efforts to a very specific location.
Another benefit of an addressable fire alarm system is that each element within the loop can be tested and monitored individually, simplifying the maintenance process. Each unit sends a signal back to the main panel to determine everything is working and “communicating” properly as opposed to narrowing a potential problem only to a specific zone.
The local building code will determine if a fire alarm system is required in a building. If a fire alarm system is required, the type and complexity of the system will be determined by that building code which in most cases refers directly or indirectly to NFPA 72 (National Fire Protection Association) National Fire Alarm and Signaling Code.
Types of fire alarm cables
The backbone of any fire alarm system is the wiring infrastructure. Fire alarm cabling has become incrementally more complex, in part driven by the trend toward mass notification, which is a factor of the fire alarm system. Mass notification—a one-way or two-way communication system in place for any emergencies affecting the public—is built on a network of secure signaling systems. Similarly, some high-tech smoke detection equipment has different electrical needs and very specific wiring requirements.
Regardless of the level of sophistication, all systems and cables must meet the National Electrical Code (NEC) and be installed in accordance with NEC article 760 as well as local regulations. The code requirements vary based on the application and the type of cable used, so it is critical to understand the implications of cable selection.
Armored Power Limited Fire Alarm Cable
Armored power limited cables are mechanically protected with steel armor for ease of installation and are UL approved so they do not need to be installed with additional mechanical protection. The steel armor protects the integrity of the cable, reducing disruption and kinks in installation leading to fewer callbacks. This armoring adds extra security for the cable in particularly harsh environments. If there is a chance of the cable getting pinched, cut, or damaged, armored cable will help protect the cable’s insulation and conductor from damage and costly repairs. Reducing the risk of damaged wires during installation or kinked circuitry of cables causing disruption helps save time and money. Instead of issuing a call back to the installer to find out where wires are failing and sending false signals, technicians can move on to the next phase of installation.
Armored Power Limited cables (FPLP) are equipped with an interlocked galvanized steel strip and are fully plenum rated for all installations up through 300 volts.
It’s important to identify fire alarm cables with an easily identifiable, unique color for quick access and a level of differentiation. Color-coding cables red was an innovation made by AFC Cable Systems in 1985 when one of the first fire alarm cables was manufactured. As a matter of fact, certain jurisdictions now require red to quickly identify if it’s an emergency circuit. In general, Power Limited Fire Alarm Cables are usually black or red for quick identification but select manufacturers can cover cables in specific colors based on building codes or specific requirements.
Fire Alarm Control Cable Type MC
Type MC Fire Alarm Control Cables serve a different purpose than Power Limited. Fire Alarm Control Cables are a traditional Type MC cable containing one or more copper grounding conductors. The cables power fire alarm devices like horns, buzzers, and strobe lights that use currents that require common sized building conductors. They are Type FPLP or Dual-Rated Type MC/FPLP and are plenum rated. This type of cable is applicable to fire alarm wiring, both for initiating circuits and signaling circuits.
Fire penetration considerations
Another factor to consider in cable selection is fire penetration approval. The fire penetration rating addresses the length of time it would take for fire to pass through a cable to breach service. Unprotected penetrations can cause the spread of smoke and fire. The National Electrical Code (NEC) requires installation of through-penetration fire stopping methods, stating, “Openings around electrical penetrations through fire-resistant rated walls, partitions, floors or ceilings shall be fire stopped using approved methods to maintain the fire-resistance rating.”
Cables play a role as one of three elements that addresses fire stopping. These elements include the fire-rated walls being penetrated, the cables creating the penetration, and the materials used to seal the penetrations that prevent the spread of fire and smoke.
A high degree of importance is placed on efficient and safe fire alarm system design. It is a matter of life and death, repair or full loss. As such, fire alarm systems have become increasingly more complex and have evolved from not just simple fire alerts but fully-integrated smart, mass notification systems. Among other things, a well-designed cabling system must adhere to code requirements and fire ratings. Due to the necessity of such notification systems, fire alarm systems must comply with rigorous routine maintenance regiments detailed by both NFPA 72 and the local authority having jurisdiction. Considerations must not only be made for a facility’s present design, but also its needs for the future. The stakes for cabling a responsive fire alarm system are high, so it is best to consult with a manufacturer on questions regarding application, installation, and code conformance.
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About the Author
Peter Lafreniere is Senior Product Manager for AFC Cable Systems, Inc., part of Atkore International. With over 27 years of experience in armored cable, he leads product strategy for the Cable Solutions business unit’s entire cable product line and is responsible for its strategic innovation initiative.
