In my September column, I provided historical background on fire alarm system components. I concluded that article stating that the next month’s article would “cover the actual installation based on Article 760 of the NEC and operation of smoke and heat detectors, as well as notification devices.”
In October, I wrote about some extremely important changes in the 2023 National Electrical Code about work spaces around electrical equipment at 1,000V or below. I have been dealing with these changes in workspace clearances with workshop clients and felt it was imperative our readers know the same basic safety knowledge. I hope I did not leave you hanging waiting for this second part.
Installation requirements for fire alarm systems and components use a combination of Article 760 in the NEC and NFPA 72, the National Fire Alarm and Signaling Code. NFPA 72 Chapter 10 includes requirements common to all fire alarm systems except for households. The following chapters in NFPA 72 provide pertinent information on installing fire alarm systems and components.
Chapter 10 applies to the broader scope of alarm and signaling systems. These requirements apply to protected premises (local) fire alarm systems, supervising station alarm systems, public emergency alarm reporting systems, emergency communications systems and carbon monoxide detection systems.
Chapter 12 addresses the performance and survivability characteristics of pathways or interconnections used in fire alarm and signaling systems.
Chapter 17 covers the design and installation criteria for all sensors and devices that recognize or are used to provide recognition of the existence of a fire or the status of a protected space and the fire protection systems within that space. An initiating device, defined in 3.3.148, refers to all forms of signal input devices and sensors, which include manually operated fire alarm boxes, automatic fire detectors, gas detectors and switches that detect the operation of a fire extinguishing or fire suppression system.
Chapter 18 includes requirements for audible and visual notification appliances for all types of systems. Notification appliance use is not limited to occupant notification; they are also used to alert and inform emergency services personnel and staff.
The objective of the system design is to achieve sufficient speed and assurance of response to a fire or supervised condition with minimal probability that such signals are the result of a nonfire or false source. System designers can achieve this objective only by selecting the proper type of initiating devices for each application and then using notification devices to warn the occupants and notify first responders. Proper location of initiating devices with correct coverage can be determined by Chapter 17’s requirements.
Once the layout of the initiating devices and notification devices is determined, NEC Article 760 in Chapter 7 is used. Article 760 covers the installation of wiring and equipment of fire alarm systems and includes all circuits controlled and powered by the fire alarm system. Informational Note 1 in 760.1 states the following: “Fire alarm systems include fire detection and alarm notification, guard’s tour, sprinkler waterflow, and sprinkler supervisory systems. Circuits controlled and powered by the fire alarm system include circuits for the control of building systems safety functions, elevator capture, elevator shutdown, door release (usually held open by electromagnets), smoke doors (usually held open by electromagnets) and damper controls, fire doors (usually held open by electromagnets) and damper control, and fan shutdown (for HVAC systems), but only where these circuits are powered by and controlled by the fire alarm system.”
Control of smoke exhaust and fresh air intake is often dependent on the fire department. More people die from smoke inhalation than from the fire.
Single- and multiple-station smoke alarms, such as those commonly installed in dwelling units, are supplied through 120V branch circuits, rather than a fire alarm signaling circuit powered and controlled by a fire alarm control panel. Branch circuits supplying power to single- and multiple-station smoke alarms are not subject to the requirements of Article 760. Fire alarm circuits from a fire alarm panel consist of nonpower-limited and power-limited fire alarm circuits.
Usually, notification devices, such as audible and visual devices, are powered by nonpower-limited circuits, while initiating devices, such as pull stations and smoke detectors, are usually connected to power-limited circuits.
Fire alarm systems, though fairly complex, are crucial first-warning systems in a fire situation. Study the NEC and NFPA 72.
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