Know Your Limits

Most professional contractors feel confident in their ability to provide design/build services for a building electrical system. They know the right questions to ask of the owner and know from both experience and the knowledge of the National Electrical Code (NEC) how to meet the owner’s goals in a safe and Code-compliant manner.

Those same professional contractors often try to design a fire alarm system, but many find the cost of what the owner wanted and what the AHJ demanded exceeds the budget of their original design. This happens for a number of reasons, beginning with the discussion with the owner about his or her fire-protection goals.

Most often, the owner does not know what they want other than to ask you to “just meet code,” and then they are unsure of what that even means. You can help the owner focus on their fire-protection goals by leading with this question, “What do you want to have left after the fire?”

This question is guaranteed to pique the owner’s interest because they assumed that just meeting code would mean the system installed by you would prevent a total loss of their building. You should understand that there are three codes that must be satisfied in order to just meet code. The building code in force in the jurisdiction will tell you what type of system the occupancy is required to have, and the NEC and National Fire Alarm Code (NFPA 72-2007) will provide the design application and installation requirements.

As stated in section 1.2.3 of NFPA 72-2007, “This Code establishes minimum required levels of performance, extent of redundancy, and quality of installation but does not establish the only methods by which these requirements are to be achieved.” [Emphasis added.]

If you design a fire alarm system that meets only the minimum requirements of these codes, you definitely will not meet the owner’s goal of preventing a total loss of their building.

That is why it is so important to ask what the owner wants to have left after a fire. Remember, the owner is not a fire protection engineer and is looking to you as the fire alarm expert. So as a designer, you must be careful not to be led down a path by an owner who does not understand the value and the limitations of a fire system.

In order to ensure you are that expert, you must know the application of all detection devices and their spacing as allowed or prescribed by the code. Even if the system is not required by a building code, NFPA 72-2007 states in section that “Non-required protected premises systems and components shall meet the requirements of this Code.” In some cases, even before you get started, the owner will ask that you also perform some “value engineering” to lessen the cost (and most likely the protection provided) of the system.

It is your job as the designer to understand the meaning of complete coverage and partial coverage, especially when using smoke detectors. NFPA 101-2006, the Life Safety Code, provides guidance in the area of total coverage in stating in section that, “Where a total (complete) coverage smoke detection system is required…, automatic detection of smoke in accordance with NFPA 72, National Fire Alarm Code, shall be provided in all occupiable areas, common areas, and work spaces in environments that are suitable for proper smoke detector operation.” Anything less than complete coverage would obviously be partial coverage.

A designer should be aware of the possibility that a fire could be larger. In a partial-coverage design scenario, detection is most often delayed for any fire remote from the detector locations in the building. Many owners believe that a few smoke detectors in the corridors will detect any fire on a floor. While this may be true eventually, the fire will almost always be large enough to at least burn out the floor before the fire department can successfully suppress it.

There are other issues a designer must understand beyond detection, including audibility and visibility of notification appliances. The code has very specific requirements in these areas. Chapter 7 of NFPA 72-2007 specifies the requirements for audibility and visibility but does not provide design guidance to ensure the designer has enough appliances in the appropriate locations to ensure compliance. Contractors are encouraged to research the design tools for the application and placement of notification appliances available from manufacturers.

If a contractor is going to provide design/build services for a fire alarm system installation and does not feel confident enough to design the system alone, then they should employ the services of a fire protection engineer or choose an equipment supplier that offers design assistance. In addition to knowing the limitations of a fire alarm system, the professional contractor is well advised to know their own limitations when designing fire alarm systems.

MOORE, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a co-editor of the current National Fire Alarm Code Handbook. Moore is a principal with Hughes Associates Inc. at the Warwick, R.I., office.

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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