Cable Substitution and Mixed Raceway in a Three-Story Office Retrofit
A three-story, 45,000 sq ft office building (42 ft tall, fully sprinklered, not a high-rise) is receiving a new addressable fire alarm system with voice evacuation. At rough-in the AHJ finds four conditions. (1) 18 AWG CL3R cable has been pulled for the signaling line circuit between floors and above corridor ceilings. (2) 18 AWG FPLR has been pulled for the 70 V speaker circuits. (3) A CAT5e cable from the fire alarm panel to the building network switch shares a 1.25 in. EMT with a 120 V circuit feeding corridor lighting for a 60 ft run. (4) The riser SLC and speaker cables pass through one sleeve between floors with no firestop. The contractor argues that CL3R is "Class 3, the same as fire alarm" and that the CAT5e is low voltage so it is fine. The entire system is power-limited. The AHJ has withheld approval pending a written position from the installing company.
1. Is CL3R acceptable for the signaling line circuit? State the code basis and the remedy.
Read the worked answer
No. The SLC is part of the fire alarm system, so NFPA 70 Article 760 governs - not Article 725. Because the system is power-limited, the SLC is a power-limited fire alarm (PLFA) circuit under Article 760, Part III, and the cable must be a listed PLFA cable: FPLR where it rises between floors, FPLP in plenums, FPL in other spaces.
CL3R is a Class 3 remote-control and signaling cable listed to Article 725. Its voltage rating and 300 V insulation are irrelevant to the question; it is not listed as PLFA cable, so it cannot be substituted for FPLR even where the copper size and circuit voltage are adequate. The contractor's "both are Class 3" argument confuses Article 725 Class 3 with Article 760 PLFA classification - they are separate articles with separate listing categories.
Remedy: remove and replace the SLC cable with FPLR (or FPLP in plenums), or, if the circuit is redesigned as non-power-limited, install it using Chapter 3 wiring methods per Article 760, Part II. Record the substitution and correction in the as-built and on the record of completion. Expect the AHJ to want the cable markings photographed at the riser before concealment.
2. Evaluate conditions (3) and (4): the CAT5e sharing EMT with a 120 V circuit, and the unfirestopped sleeve.
Read the worked answer
Condition 3 - not acceptable. The CAT5e to the network switch is a communications circuit under Article 800. Communications cables must be separated from electric light and power conductors by at least 2 in. (50 mm), or by a listed barrier, and a shared raceway with a 120 V branch circuit provides neither. Article 760 also restricts PLFA conductors from sharing raceways, boxes, or compartments with power and Class 1 conductors absent a barrier. The fact that the CAT5e carries only low-voltage data does not create an exception.
Remedy: pull the CAT5e in its own raceway, or use a listed divider. Separately confirm the Ethernet drop is protected and identified; it is not fire alarm cable and must not be treated as part of the FA system pathway.
Condition 4 - not acceptable. Penetrations of fire-rated assemblies must be firestopped to the rating of the assembly using a listed system. Cables passing through a sleeve between floors with annular space left open defeats the floor's rating and is also a pathway survivability issue. Install a listed firestop system, inspect it, and document it.
3. The contractor proposes upgrading the riser to two-hour circuit integrity cable "to be safe." Is that required, and how do you evaluate it?
Read the worked answer
Not required here, and unnecessary cost. NFPA 72 assigns pathway survivability levels; Level 1 is the default for a protected premises system. Level 2 (2-hour circuit integrity, or an equivalent protected pathway) is triggered by the building or life safety code - typically a high-rise, a system designed for partial evacuation or relocation, or an AHJ requirement.
This building is 42 ft and three stories, so it is not a high-rise, and the design does not rely on partial evacuation. Level 1 is appropriate, with FPLR cable in the riser. What is required regardless of level is that the riser be properly enclosed and firestopped where it penetrates rated construction, and that the speaker circuits be installed as PLFA circuits (FPLR is correct) - or by Chapter 3 methods if the speaker circuit is ever redesigned as non-power-limited.
If the owner chooses Level 2 anyway, it must be a listed circuit-integrity system installed per its listing, not simply "better cable," and the survivability level must be stated on the drawings. Making a voluntary upgrade without documenting it invites the next inspector to assume a requirement that does not exist.