13.4 Fire Alarm, Communications & Optical Fiber Systems (Articles 760, 770, 800-820)

13.4 Fire Alarm, Communications & Optical Fiber Systems (Articles 760, 770, 800–820)

Exam Focus: NPLFA versus PLFA circuits, the red disconnect identification and the GFCI/AFCI prohibition, FPL cable types and substitutions, abandoned cable removal, communications bonding and grounding, and the Michigan fire alarm licensing overlay.

Chapters 7 and 8 close out the power-limited subject on the PSI blueprint. Article 760 sits in Chapter 7; the communications articles sit in Chapter 8, which under 90.3 is independent of Chapters 1 through 7 except where Chapter 8 specifically references them.

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Fire Alarm Systems — Article 760

Article 760 divides fire alarm circuits into two families based on how the power is limited.

The Supply Circuit Rules — 760.41(B) and 760.121(B)

These two rules appear on examinations constantly because they are counterintuitive:

+-------------------------------------------------------------------------+
|              THE FIRE ALARM SUPPLY CIRCUIT (760.41 / 760.121)           |
|                                                                         |
|   [X] The branch circuit supplying fire alarm equipment SHALL NOT be    |
|       supplied through GROUND-FAULT CIRCUIT-INTERRUPTER or              |
|       ARC-FAULT CIRCUIT-INTERRUPTER protective devices.                 |
|                                                                         |
|   [X] The circuit disconnecting means SHALL:                            |
|         - have RED identification                                       |
|         - be ACCESSIBLE ONLY TO QUALIFIED PERSONNEL                     |
|         - be identified as "FIRE ALARM CIRCUIT"                         |
|                                                                         |
|   [X] The RED IDENTIFICATION shall not damage the overcurrent device    |
|       or obscure the manufacturer's markings.                           |
|                                                                         |
|   WHY: a nuisance GFCI or AFCI trip would silently disable the fire     |
|   alarm system. Reliability of the supply outranks the leakage risk.    |
+-------------------------------------------------------------------------+

The branch circuit must also supply no other loads, and it must not be supplied through a switch other than the identified disconnecting means.

Identification of Fire Alarm Circuits — 760.30

Fire alarm circuits must be identified at terminal and junction locations in a manner that helps prevent unintentional signal interference during testing and servicing.

Other Article 760 Rules

• 760.24 Mechanical execution: neat and workmanlike installation, supported by the building structure, not secured to or supported by raceways.
• 760.25 Abandoned cables: the accessible portion of abandoned fire alarm cable must be removed.
• 760.136: separation of power-limited fire alarm conductors from electric light, power, Class 1, and non-power-limited fire alarm conductors, with the same family of exceptions as 725.136 (barriers, 0.25 in separation, reclassification).
• 760.176 / 760.179: listing and marking requirements for NPLFA and PLFA cables, including the substitution hierarchy in which plenum cable may be used in riser and general locations but not the reverse.

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Optical Fiber Cables — Article 770

Optical fiber carries no current, but the cable may contain metallic members, and that is what the NEC regulates.

Key rules:

• 770.93: the non-current-carrying metallic members of an optical fiber cable entering a building must be bonded or grounded, or interrupted by an insulating joint, as close as practicable to the point of entrance.
• 770.133: conductive and composite optical fiber cables must be separated from electric light and power conductors, with the familiar barrier and separation allowances.
• 770.25: abandoned optical fiber cable must be removed.

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Communications Systems — Articles 800 through 840

The 2020 NEC reorganized Chapter 8 so that Article 800 carries the general requirements shared by all communications systems, with the specific systems following:

Bonding and Grounding — Article 800 Part IV

• A primary protector is required on aerial communications conductors that may be exposed to accidental contact with power conductors or to lightning.
• The bonding conductor or grounding electrode conductor for communications must be not smaller than 14 AWG, listed, and have a current-carrying capacity not less than the grounded metallic sheath member and protected conductors of the cable.
• In one- and two-family dwellings, the bonding conductor or grounding electrode conductor must be as short as practicable, not exceeding 20 ft (6.0 m) in length. Where that length cannot be met, a separate ground rod may be driven and bonded to the power grounding electrode system with a conductor not smaller than 6 AWG copper.
• The communications bonding must connect to the building's intersystem bonding termination required by 250.94, which is why services installed since the 2008 NEC carry an external lug assembly for that purpose.

Separation Rules

• Lightning conductors: communications cables and equipment must maintain a separation of at least 1.8 m (6 ft) from lightning protection system conductors where practicable.
• Power conductors: communications conductors must be separated from electric light and power conductors in raceways, boxes, and enclosures using the same barrier and separation methods described for Class 2 and Class 3 circuits.
• Abandoned cable: the accessible portion of abandoned communications cable must be removed (800.25).

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The Michigan Licensing Overlay

Fire alarm work is a separately licensed activity in Michigan under the Skilled Trades Regulation Act:

Note two examination facts covered in Chapter 10: the fire alarm specialty technician examination is a separate PSI examination with its own question count, subject list, and passing score, and fire alarm specialty technician and contractor candidates have unlimited attempts within one year, unlike master, journeymen, and sign specialist candidates who are limited to two.