Networking by the Book

Like many engineering disciplines, the fire protection world is built on tradition. And while tradition provides stability and uniformity, it also explains why the fire protection community has moved toward new technology applications at glacial speed. One advantage of this measured move to recognize new technology ensures that whatever the codes and standards finally endorse will have proven reliable and will offer the expected life safety functions.

In bringing new technology into the fire alarm industry, many will first try to “force” the new technology to meet the tried-and-true requirements already found in NFPA 72, the National Fire Alarm and Signaling Code.

For example, in NFPA 72 2013, the code began to address pathways that represent new technology, such as Ethernet, local area networks (LAN), wide area networks (WAN), and Internet connections. The Technical Committee developed a new class of signaling pathway labeled Class C. The code defines the operation of a Class C pathway as follows: “12.3.3* Class C. A pathway shall be designated as Class C when it performs as follows:

“(1) It includes one or more pathways where operational capability is verified via end-to-end communication, but the integrity of individual paths is not monitored.

“(2) A loss of end-to-end communication is annunciated.”

And the Annex clarifies the section under A.12.3.3: “The Class C reference is new and is intended to describe technologies that supervise the communication pathway by polling or continuous communication ‘handshaking’ such as the following:

“(1) Fire alarm control unit or supervising station connections to a wired LAN, WAN, or Internet

“(2) Fire alarm control unit or supervising station connections to a wireless LAN, WAN, and Internet

“(3) Fire alarm control unit or supervising station connections to a wireless (proprietary communications)

“(4) Fire alarm control unit digital alarm communicator transmitter or supervising station digital alarm communicator receiver connections to the public switched telephone network

“Individual pathway segments are not required to be monitored. Supervision is accomplished by end to end communications.”

Unfortunately, the code offers no other guidance as to where Class C pathways would be used in a fire alarm system or mass notification system network in a building. The only time the code uses the term “network” appears in the definition of a “life safety network.”

The code defines a life safety network as “a type of combination system that transmits fire safety control data through gateways to other building system control units.” The code also defines a “gateway” as “a device that is used in the transmission of serial data (digital or analog) from the fire alarm control unit to other building system control units, equipment, or networks and/or from other building system control units to the fire alarm control unit.” From these two definitions, you can see that, essentially, the code only recognizes the use of a network for the interconnection of fire alarm control units to other building system control units.

The code provides the requirements for a fire alarm system if it serves as a component of a life safety network, if it communicates data to other systems providing life safety functions, or if it receives data from such systems. In these three cases, the code requires the system to monitor the integrity of the pathway used for communicating data. This includes monitoring the physical communication media and monitoring the ability to maintain intelligible communications. Any systems that integrate with a fire alarm system must provide that the data received from the network cannot affect the operation of the fire alarm system other than to display the status of life safety network components.

Finally, where nonfire alarm systems interconnect with the fire alarm system using a network or other digital communication technique, the arrangement must generate a signal (e.g., heartbeat, poll, ping, query) between the fire alarm system and the nonfire alarm system. The failure of the fire alarm system to receive confirmation of the transmission must initiate a trouble signal within 200 seconds.

So, once again, the code-makers have somewhat “forced” a new technology—the Ethernet and LAN or WAN wiring—to meet existing copper wiring requirements. To address a careful examination of the need to change these requirements in the developing 2016 edition of NFPA 72, the National Fire Alarm and Signaling Code, the NFPA Technical Correlating Committee on Signaling Systems for the Protection of Life and Property established a network task group to review the issues and develop proposals.

Most discussion in the fire alarm community still revolves around wanting assurance that the network will prove as reliable as current fire alarm system wiring configurations. As the discussions move forward, the types of networks that may first prove acceptable will include the dedicated networks that will integrate the fire alarm and mass notification systems. It seems doubtful that the code will permit the use of public networks due to the inherent potential downtime associated with them. As you might guess, the fire alarm community will not accept large amounts of downtime for a system for the obvious impact such downtime might have on the protection of life and property.

The early discussions of this new task group have centered on the application of Ethernet as a way to talk to devices or appliances, such as speakers. Some members feel this will represent a less commonly used application than using Ethernet as a way to talk between control equipment. Yet, some equipment already on the market uses Ethernet and power over Ethernet (PoE) to operate speaker systems.

Other issues that the task group will address will include the switches and routers and their compliance with NFPA 72 equipment requirements as well as the issue of sharing network bandwidth between life safety and other applications.

Category 5 cable—typically used in Ethernet configurations­—is galvanically isolated. Many fire alarm community members believe that Cat 5 does not need ground-fault protection, as expected with standard copper circuits. The task group also will review the concepts of end-to-end communications and redundancy as methods to ensure reliability of these configurations.

As presented to the task group by one of its members: “The operational conditions of the pathway include factors such as Latency, Throughput, Response Time, Arrival Rate, Utilization, Bandwidth, and Loss. It is intended that the Life Safety equipment connected to a network actively monitor some or all of the pathway’s operational conditions, so that an improperly installed or configured pathway, or network of pathways, is detected by the life safety equipment, and reported as a Trouble. This monitoring is intended to be continuous such that a degradation of pathway performance over time is detected and reported. Trouble would be reported when operational conditions of the pathway(s) have deteriorated to the point where the equipment is no longer capable of meeting its minimum required performance requirements, even if some level of communication to end point devices is still maintained. Examples of performance requirements include the activation of an alarm within 10 seconds, the reporting of a Trouble within 200 seconds, synchronization of strobes, and delivering audio messages with required intelligibility.

“It is worth noting, that it is possible to have a pathway, where end-to-end communications is operational under system idle conditions, but in the event of an alarm, the increased load on a degraded pathway could cause a partial or complete failure to deliver the required Life Safety signals. This is the situation intended to be actively detected and reported.”

When you intend to use a network to interconnect your customer’s fire alarm or mass notification systems, you must give a great deal of thought to operational reliability. In addition, you must give attention to other issues in the planning stage of your system installation. These include receiving approval from the authority having jurisdiction for your performance alternative to the current code requirements and correctly installing the cable.

Integration using Ethernet or networks definitely remains on the horizon. Learn as much about these systems as you can to stay competitive and to set yourself apart from your competition.

About the Author

Wayne D. Moore

Fire/Life Safety Columnist
Wayne D. Moore, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a principal member and past chair of NFPA 72, Chapter 24. Moore is a vice president with JENSEN HUGHES at the Warwick, R.I., office. He c...

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