Test Mechanics

Having the right tools makes any job easier. As any electrician entering the field learns, he or she must have the right tools to perform electrical work efficiently. This same rule applies to installing a fire alarm system. With the advent of computer-based fire alarm systems, the types of tools change. In addition, a contractor must use different test methods to ensure that he or she has installed the fire alarm system correctly.

As with many electrical devices and systems, fire alarm systems have differing, but acceptable, methods to test the devices, appliances and systems.

NFPA 72-2002, Chapter 10 provides specific guidance regarding test methods for the various components of a fire alarm system. Starting with the cable, Table 10.4.2, Test Methods, describes the minimum testing methods used to ensure the wiring will perform correctly.

For metallic conductors, the contractor must make measurements for stray voltage, ground faults, short circuit faults and loop resistance and must make tests to verify that the fire alarm system properly monitors each circuit for integrity.

The National Fire Alarm Code requires that the contractor test all installation conductors with a volt/ohmmeter to verify the absence of stray voltages between installation conductors, or between installation conductors and ground. Unless the equipment manufacturer’s specifications require a different threshold, the code requires that the maximum allowable stray voltage not exceed 1 volt AC/DC.

Although some contractors may feel the need to use a meg-ohm test instrument, the code does not require its use. Obviously, if a contractor suspects that some compromise has occurred to the conductor insulation, from either installation damage or manufacturing damage, then the contractor may wish to use a meg-ohm tester.

Testing and measuring the loop resistance of each circuit will help ensure that an excessive voltage drop will not affect the operation of devices or appliances. The standard test required by NFPA 72-2002 starts with each initiating and indicating circuit installation conductor pair short-circuited at the far end.

The contractor then measures and records the resistance of each circuit. The contractor must also verify that the loop resistance does not exceed the installed equipment manufacturer’s specified limits.

The code requires that the fire alarm system control unit monitor the integrity of all connected circuits. Any fault introduced in any circuit monitored for integrity must result in a trouble indication at the control unit.

The National Fire Alarm Code requires that the contractor open one connection at not less than 10 percent of the initiating devices, notification appliances and controlled devices on every initiating device circuit, notification appliance circuit and signaling line circuit to ensure that the circuit monitoring for integrity works properly.

After the contractor tests the wiring, he or she will need to test 100 percent of the balance of the fire alarm system. Such a complete test ensures the system providing life safety to the occupants and protection for the building will work as specified and as required by the code.

Chapter 10 requires the contractor to use specific methods when testing devices. Specifically, the contractor must test smoke detectors in place to ensure smoke entry into the sensing chamber and an appropriate alarm response. Testing with smoke or listed aerosol approved by the manufacturer offers acceptable test methods.

After the first year of installation, the code also requires sensitivity testing of installed smoke detectors and allows the contractor to perform any of the following tests “to ensure that each smoke detector is within its listed and marked sensitivity range:

  1. Calibrated test method
  2. Manufacturer’s calibrated sensitivity test instrument
  3. Listed control equipment arranged for the purpose
  4. Smoke detector/control unit arrangement whereby the detector causes a signal at the control unit when its sensitivity is outside its listed sensitivity range
  5. Other calibrated sensitivity test method approved by the authority having jurisdiction.”

The professional contractor’s toolbox will want to include a sound level meter that meets ANSI S1.4a, Specifications for Sound Level Meters. The code requires the contractor to measure and record the sound pressure level of audible notification appliances throughout protected area.

The professional contractor knows the importance of having these tools to ensure compliance with the code and to help ensure the fire alarm system will work properly when called on. Make sure you have the “tools of the trade.” EC

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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