Analog addressable fire alarm systems compared to conventional systems

Key Concepts

Unlike conventional alarms, analog addressable systems allow an exchange of data between the panel and the activated sensor or sensors.

Due to drift compensation, analog addressable systems are less likely to experience false alarms.

When selecting a system, choose the type of detector that fits your needs and your budget.

Sections: System differences Drift compensation Analog system installation Choosing a system More Info:

Sidebars: Guidelines for buying a fire alarm system

Advancements in technology are making analog addressable fire alarm systems appropriate for all sizes of applications — not just the large ones. Unlike older addressable systems, newer analog addressable products are just as easy to program as conventional systems, and are also easy to maintain. The new analog addressable systems, with their ease of installation and maintenance, are fast becoming the choice of the future.

System differences

An addressable fire alarm system provides the user with the status of the initiating devices that comprise the system network; that is, smoke detectors, water flow switches, etc. The fire alarm system control unit allows the user to easily view the system status and features information about the emergency device as well as detailed information about the device’s “address.” The system hardware or software can also assign digital addresses for each device. The location of an operated addressable device is communicated via annunciation, printout, or other communication, and is also visibly indicated according to building, floor fire zone, or other approved subdivision.

An analog addressable system has all the characteristics and features of an addressable system, but expands on the information provided to the control panel. Detectors in an analog addressable system become “sensors” that relay information to the control panel regarding how much smoke or heat the detector is sensing. The control panel is then able to make action decisions based on this higher level of information, including when or when not to go into alarm mode.

What separates an analog addressable system from a conventional system is that it allows an exchange of data between the panel and the activated sensor or sensors. Conventional systems feature groups of initiating devices combined into individual zones grouped on a single loop and linked to a control panel (Fig. 1). These systems feature lower initial costs, but deliver far less information about activated devices and are unable to identify individual trouble spots (the operator must manually identify the problem area).

Unlike conventional systems, analog addressable devices can pinpoint a fire’s “address,” greatly accelerating the potential speed of response. This information is annunciated locally and communicated digitally to the central station or fire department. There is no need to manually track down the activated device on foot.

Because detectors in an analog addressable system act as “sensors” that exchange information, the right action is instantly set in motion at the control panel. The sensitivity level of these devices is completely at the system manager’s control. For instance, the sensitivity level might be lowered at night when an area is unmanned and raised during the day.

Drift compensation

Unlike conventional alarms, which can get false readings from the accumulation of dust and other contaminants, analog detectors are able to self-compensate for these smoke-reading inhibitors, thus making them far less prone to false alarms. With this “drift compensation,” analog detectors are able to distinguish between a long-term drift in smoke detection due to contaminants and a short-term change in smoke detection resulting from a real fire. To ensure that system sensitivity remains consistent and that detectors can function at the proper levels day in and day out, analog detectors can be adjusted.

Analog system installation

Analog addressable systems are surprisingly simple to install and maintain despite their advanced capabilities. In fact, a complete analog addressable system, known as the SLC loop or signaling line circuit, can run on a single pair of wires depending on system size (Fig. 2). This type of system also allows the use of T-Tapping, which cannot be done on a conventional system. A conventional system will have many pairs of wires, all coming back to the main panel. The installation of analog addressable wiring is easier, and the maintenance and trouble-shooting costs are dramatically lower.

Because of the simplicity of the wiring and the analog addressable system’s ability to pinpoint a real problem (and separate it form a dust-related problem), maintenance requires less manpower, takes less time, and is more likely to fix the problem the first time. This all leads to lower service costs, better performance, and, as a result, improved life safety. The simplicity of the analog addressable system also leads to greater flexibility, both in terms of programming options and opportunities for expansion.

Choosing a system

There are a variety of features and options from which to choose, even within the realm of analog addressable systems. It is best to pick the type of detector that is right for your needs and budget, as well as the right control panel. You’ll then need to wade through all the available system features — everything from different interfaces to built-in digital communicators to automatic sensitivity checks and maintenance alerts.

The bottom line is this: If you have a sizable facility to protect, the conventional fire alarm system is not necessarily the best option. In pursuit of maximum safety and value, more and more facility managers are breaking with convention and pinpointing analog addressable systems as their systems of choice.

More Info:

The authors can be contacted for questions. Jack Grones and Brian Foltz can be reached at jack_grones@silentknight.com and brian_foltz@silentnight.com , or 800-328-0103. Article edited by James Silvestri, Managing Editor, 630-288-8777, jsilvestri@reedbusiness.com .

Guidelines for buying a fire alarm system

Purchase a system that is appropriate for your needs. Don’t overkill the problem

Lay out the system in advance. Determine how many addressable devices you need, and what type: smoke detectors, heat detectors, relay modules, pull stations, and various monitoring switches

Give yourself room to grow. If you need 25 devices, purchase a system that supports at least 15%-20% more than that in anticipation of future growth

Be sure that you feel comfortable with the system and its operation. The controls should be simple to use and laid out in a way that makes practical sense

Buy a system that you’ll be happy with for an extended period of time — at least 5-10 yr. Be prepared to add on to the system before you have to replace it.

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