CL3R is the abbreviation for Class 3 Riser Cable, a type of low-voltage, power-limited wiring designed for vertical riser applications between floors in commercial or industrial buildings. These cables are rated for up to 300 volts and are manufactured to prevent the spread of fire from one building level to another.
Class 3 Riser (CL3R) cables fall under the Class 3 category of power-limited circuit wiring, as defined by the National Electrical Code (NEC). They are designed to safely transmit signals and low-voltage power for systems that operate up to 300 volts while meeting flame-retardant requirements suitable for riser shafts or vertical pathways between floors. CL3R cables are typically insulated and jacketed with flame-resistant materials such as polyvinyl chloride (PVC) or riser-rated thermoplastic compounds.
The “R” in CL3R stands for riser-rated, indicating that the cable has passed specific flame tests that measure vertical burn performance. These tests, such as the UL 1666 flame test, confirm that CL3R cables can limit fire propagation between floors, making them safe for use in vertical building shafts or walls. While CL3P (plenum-rated) cables meet stricter fire and smoke performance standards, CL3R remains the standard for most non-plenum vertical installations where air circulation is not a factor.
Regulated under the National Electrical Code (NEC), specifically Article 725, which outlines construction and application standards for Class 2 and Class 3 power-limited circuits. Underwriters Laboratories (UL) provides certification and testing through UL 13 and UL 1666 to ensure compliance with national fire safety and performance requirements.
The development of CL3R cables originated from evolving fire safety codes introduced in the 20th century as multi-story commercial construction became more common. The introduction of riser-rated cabling provided a safer alternative to general-use cables, reducing the risk of fire spreading vertically through conduit or open shafts. This classification became an industry standard as building designs incorporated larger and more complex electrical and communication systems.
These cables are suitable for non-plenum spaces that require reliable electrical performance and flame resistance but do not involve air-handling ducts or plenums.