Understanding Residential Fire Alarm Systems

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In the sleeping areas the notification appliance must meet the above or have a sound level of 75dBA, whichever is greater, as measured at the pillow.

Installers are reminded that had single or multiple station smoke alarms been installed in this residence that each smoke alarm’s integrated sounder would have ensured compliance with the codes notification requirement, but due to the installation of a fire alarm system, notification appliances were necessary to accomplish the same requirement.

Additional consideration should be made in selecting sounding devices which are listed and designed for the intended purpose. This means using alarm sounders and sirens which are listed for Household Fire Alarm Systems.

Combination System – In this era of programmable systems, most residential alarm systems are capable of performing multiple functions, from intrusion detection, to medical emergency notification, to controlled access and fire detection.
Installers are reminded that although the code allows for the use of combination systems in household applications, the code is very specific on the conditions under which these Household Fire Alarm Systems must operate.
Specifically, these systems must:

• Use equipment which is listed for the intended purpose.  (NFPA 72(07)-11.3.1)   This means that the system must be listed for use as a Household Fire Warning System (UL 985). 
• Ensure that fire signals take precedence over any other signal or function, even if the non-fire signal activates first. (NFPA 72(07)-11.7.6.2)
• Have two independent power sources, one which is the commercial light and power and the second that consists of a rechargeable battery. (NFPA 72(07)-11.6.2 (1))
• The secondary power source must be capable of powering the system for at least 24 hours in normal conditions followed by four minutes of alarm. (NFPA 72(07)-11.6.2 (2)) Additionally, it must be supervised for removal, disconnection or a low battery condition. (NFPA 72(07)-11.6.2 (3)) And it must be capable of recharge within 48 hours. (NFPA 72(07)-11.6.2 (4b))
• Possibly the most important item to consider is that a combination system providing only intrusion detection would best be described as a “burglar alarm,” but introduce just one fire detection device to the system and it now becomes a “household fire alarm system” which also provides intrusion detection.
In plain terms this means that the installer absolutely must consider what type of system this will be before running any wires or purchasing any peripheral equipment.

System Wiring – Where common wiring is employed for a combination system, the equipment for other than the fire alarm system shall be connected to the common wiring of the system so that any fault in this equipment or interconnection between this equipment and the fire alarm system wiring does not interfere with the supervision of the fire alarm system or prevent alarm or trouble signal operation.  (NFPA 72(07)-11.7.6.5)
What this means to the installers is that all wiring associated with the “fire alarm” portion of the system must be installed in accordance with NFPA 70, National Electrical Code, Article 760.  (NFPA 72(07)-11.8.5)

This includes such peripheral devices as:
• System keypad
• System transformer
• System notification appli-ances (sounders)
• All devices “powered” by the fire alarm system (this could mean your security system devices if they share power from the system integral power supply).  If this is unacceptable, then the installer may segregate the security devices to an auxiliary power supply used solely for the security devices, and independent from the fire devices powered by the control panel.

It should also be noted that had this system originally been installed as a security only system and the fire detection added subsequently, the installer would need to potentially replace some of the system wiring with fire-rated wiring.

Alarm Monitoring – Where it is desired to connect the household fire alarm system to a remote monitoring station, this service also is regulated through various sections of the code.