Fire alarm cabling has become incrementally more complex over the years, in part driven by the trend toward mass notification, which is a factor of the fire alarm system. Mass notification — a one- or two-way communication system in place for any emergencies affecting the public — is built on a network of secure signaling systems.
According to a 2019 State of the Market: Fire Alarm report, “For fire alarms, this means greater integration between the building, mass notification, and suppression systems. But ultimately what drives the fire market is codes and laws, and that will likely never change.”
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 sensors. The sensors 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 or through smoke transmission, heat receptors, carbon monoxide detection, etc.
Types of fire alarm systems
Within commercial buildings, there are two types of fire alarm systems: conventional and addressable. The goal of any fire alarm system is to prevent loss and increase safety, but there are reasons why one might be used over the other.
Conventional fire alarm systems: Conventional alarm systems are the most traditional. They are well-proven solutions for fire protection but lack the technology and sophistication that the industry has embraced for the last 15 years. Conventional systems require individual wires for every audio and visual device that connects back to the main fire panel. Since each signal requires a cable, cabling and labor costs (as well as testing and inspection costs) may increase. This type of system is often more suitable as a viable fire notification for smaller installations rather than large facilities because 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 panel in a loop by a singular wire with various smoke, fire, gas, security breach detection, and notification devices. Addressable fire systems provide pinpointed locations of the potential emergency. Since each device has its own “address,” the activated device instantly triggers a specific location notification. Because of its ability to pinpoint specific locations quickly, this type of installation often works best in commercial, high-rise, or multi-dwelling buildings in which the size of the building can complicate rescue efforts.
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.
Types of fire alarm cables
Furthering the complexity of fire alarm systems are the various types of cables that connect the fire panel to audio and visual devices. Depending on the type of fire alarm that is best suited for the building, its size and function will determine the necessary type of cable. Take, for instance, the quality of sound and audio in verbal warning systems. A higher quality of sound requires a different type of cable. A 14-gauge cable is required for sounders and strobes, while a smaller gauge is acceptable for speakers. There is also another set of requirements for voice intelligibility quality. The more quality you need in the system, the more sophisticated the wiring.
Regardless of the level of sophistication, all systems and cables must meet the National Fire Protection Association (NFPA) codes as well as local regulations. More specifically, the 2019 version of NFPA 72 was updated to cover “the application, installation, location, performance, inspection, testing, and maintenance of fire alarm systems, fire warning equipment and emergency warning equipment, and their components.”
The codes are different based on the application and the type of cable used, so it is critical to understand the implications of cable selection.
Power-limited fire alarm cable: Power limited is the dominant cable in the market and is permitted by the NEC as suitable for general-purpose fire alarm use with a few exceptions. These types of cables are UL-approved by themselves and meet code requirements for installation without armor or mechanical protection.
Armored power-limited fire alarm cable: Certain applications call for heavier duty protection. 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. Armored power-limited cables are equipped with an interlocked galvanized steel strip and are fully plenum-rated for all installations up through 300V. In general, power-limited fire alarm cables are usually black or red for quick identification, but cables can be manufactured 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. However, its armor is not an equipment grounding means. 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 or remote control hook-ups connecting the main fire alarm control panel with pull stations, smoke detectors and alarms, and remote control circuits from magnetic motor starters, contractor, relays, and signals.
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 a fire-rated assembly such as a wall or ceiling. 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 address fire stopping, including 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.
Rightfully so, there is a high degree of importance 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 evolved from simple fire alerts to fully integrated smart, mass notification systems. Among other things, a well-designed cabling system must adhere to code requirements, fire ratings, and UL codes; undergo routine maintenance; and be built to spec. The stakes for a responsive fire alarm system are high, so it is best to consult with a manufacturer on questions regarding application, installation, and code conformance.
Raymond Horner is director of codes and standards for Atkore, Inc. He is involved in multiple product standard development committees including UL 2196 for 2-hr fire ratings. He sits on Code-Making Panels No. 3 and No. 5 of the National Electrical Code and Section 12 and the Part 1 committee of the Canadian Electrical Code. He can be reached for questions at [email protected].
