Two-for-One Special

There are two basic categories of alarm panels on the market today: residential and commercial. Commercial panels, whether single- or dual-use combination, must be tested by a third-party organization, such as Underwriters Laboratories (UL) of Northbrook, Ill. This ensures the panel in question complies with established national burglar alarm standards and fire codes.

There are several significant differences between the single-use burglar-only panel I discussed last month and the dual-use commercial combination panels I’m looking at this month. Most notable is the color of the metal can that houses the motherboard. By code, red denotes fire, so when fire is involved, even when it is part of a commercial burglar alarm system, the outer can usually is red.

Another difference is how primary power is applied to a combination panel itself. Burglar-only alarm panels use a plug-in, step-down transformer, whereas combination panels usually contain a stationary frame transformer within the metal can. In this case, 120 volts alternating current is provided to the transformer using a pigtail connection. National Fire Protection Association (NFPA) 72, the National Fire Alarm Code, allows for a separate plug-in transformer, but it must be secured to the receptacle and have a protective shroud or housing that protects it from physical damage.

The breaker that feeds power to a combination panel also must comply with the code. Section, NFPA 72-2007, requires the breaker to be physically protected from accidental shutoff using a lock-on accessory feature. Also, this breaker must be clearly marked with red for easy, quick identification.

Still yet, the listing is another difference between a commercial burglar-only and a combination panel. A small sticker inside the alarm panel box provides this information. To verify the authenticity of the listing, you must go to the third-party organization that issued it, such as UL.

Today, security firms commonly install combination fire/burglar alarm panels in small to mid-size installations. Integrating fire and security ensures a more cohesive approach with a single--user interface instead of two. This streamlines command and control, so the end-user must learn to operate one system only.

In the past, fire inspectors often refused to allow this arrangement in new construction, partially because early code editions did not support the use of the combination panel approach. Now, however, according to Section of NFPA 72-2007, “Protected premises fire alarm systems that serve the general fire alarm needs of a building or buildings shall include one or more of the following systems or functions: ... (8) Guard’s tour supervisory service ... (11) Combination systems.”

Section also provides direction: “Fire alarm systems shall be permitted to share components, equipment, circuitry and installation wiring with non-fire alarm systems.”

There’s more. Section specifies that when combining functions in this manner, “Operation of 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.”

In other words, fire must take precedence. Nonfire devices must not impact the proper operation of the fire alarm portion of the system, and it must not interfere with local notification. And when devices are used that may adversely affect fire operations, they must be listed for fire even if their primary function is not related.

There still are a few authorities having jurisdiction (AHJs) in the field who continue to insist on functional separation, requiring a dedicated fire alarm panel even though fire code allows otherwise. Because NFPA 72 provides a minimum course of action, these AHJs are well within their rights to require separate alarm panels if they so choose.

But what about the circuits themselves? The two basic types of alarm circuits in use today are conventional and addressable. Conventional panels use zones, or initiating device circuits (IDCs); addressable panels use points connected to signaling line circuits (SLCs). Identification of alarms and devices for the latter is by individual point; in the former, it occurs by a group of devices on a specific IDC. Obviously, addressable systems provide more information for the user or occupant.

On the addressable side, it is permissible by code to place both fire and burglar detection devices on the same SLC, but when you do, you must use isolation modules on the latter to ensure the circuit’s integrity. Another way to maintain integrity is to use two different SLCs. Some panels come with two, but in others, you must add a circuit board.

Using the two-SLC approach, one circuit is used for fire and the second for security. In this manner, if something should happen to one of the addressable burglar alarm monitoring modules, the fire SLC will continue to work normally, which is one of the prerequisites of a combination panel listed for fire (see Section, NFPA 72-2007).

COLOMBO is a 35-year veteran in the security and life safety markets. He is director with and a nationally recognized trade journalist in East Canton, Ohio. Reach him at

About the Author

Allan B. Colombo

Freelance Writer
Allan Colombo is a 35-year veteran in the security and life safety markets. He is director with and a nationally recognized trade journalist in East Canton, Ohio. Reach him at

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