[IMAGE]12183[/IMAGE]Although Annex A contained in NFPA 72, 2010, is not mandatory, it does provide important information that you need to follow, often to the letter. Although the following quote deals with systems listed for “mass notification,” this type of system often serves the fire detection mission as well.
Section A.18.104.22.168, Fire Alarm Control Interface, says, “Some mass notification systems’ autonomous control units (ACUs) might not be listed to UL 864 for fire alarm service. Any component that is connected to the fire alarm system must be connected through a listed interface that will protect the functions of other systems should one system experience a failure. This can be through isolation modules, control relays, or other approved means that are listed for the intended use. As an example, failure of a stand-alone ACU should not affect any function of the FACU.”
Observe Pathway Rules Under 72
The general rules of the road for signal pathways involving Class A, B, and X, under NFPA 72, 2010, are as follows:
Section 23.6.2 — An open, short circuit, or ground fault shall result in the annunciation of a trouble signal.
Section 23.6.3 — Class B pathways shall maintain alarm capability during the application of a single ground fault.
Section 23.6.4 — Class A and Class X pathways shall maintain alarm capability during the application of a single ground fault, and also during the combination of a single open and a single ground fault.
Section 23.6.5 — Where digital communications are used, inability to send or receive digital signals over a signaling line circuit shall be indicated by a trouble signal.
In closing, my final suggestion to the individual who wrote in with the fire alarm SLC problem is to first check the number of conductors in the FPL cable in the hope that four are present and only two are in use. In this case, you may be able to utilize the spare set. Secondly, if this does not prove helpful, you will have to install isolation modules, which is probably more cost effective than running another two- or four-conductor cable.
Al Colombo is an award-winning writer who has covered electronic security and life safety since 1986. Visit his Web site at www.alcolombo.info, and check out his Security Sense blog.
The Case for Combination Fire Alarm Systems
Despite what some diehard veteran fire alarm professionals will tell you, combination fire/burglar alarm systems are allowable under NFPA 72, National Fire Alarm and Signaling Code, 2010 Edition. However, there are rules that you must know and follow.
First, in Section 22.214.171.124 of NFPA, a combination fire alarm system is defined as, “A fire alarm system in which components are used, in whole or in part, in common with a non-fire signaling system.” This type of system uses a data multiplex communication technology that centers on what we commonly call addressable sensors, detectors and monitoring input modules for both fire and burglar alarm functions.
Additionally, Section 126.96.36.199, NFPA 72, 2010, says, “Fire alarm systems shall be permitted to share components, equipment, circuitry, and installation wiring with non-fire alarm systems.”
Here’s the catch — your burglar alarm devices cannot in any way interfere with the proper operation of the fire alarm portion of the system. Section 188.8.131.52, NFPA 72, 2010, offers this warning: “Operation of a non-fire system function(s) originating within a connected non-fire system shall not interfere with the required operation of the fire alarm system, unless otherwise permitted by this Code.”
Admittedly, there are advantages to using separate fire and burglar alarm systems. In fact, there was a day when fire authorities refused to consider the use of combination systems in commercial venues. And then, when combination systems were deemed allowable in NFPA 72, it took a decade or more for many of these same fire inspectors to actually accept them.
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