CL2R is the abbreviation for Class 2 Riser Cable, a type of low-voltage cable approved for use in vertical riser applications between building floors. These cables are engineered to meet fire-resistance standards that prevent the vertical spread of flames through riser shafts and building cavities.
Class 2 Riser (CL2R) cables are designed for power-limited circuits that carry voltages up to 150 volts. They are constructed with insulation and jacket materials specifically tested for fire safety in vertical spaces, such as elevator shafts, cable risers, and utility chases, where a fire could quickly spread between floors. While not as flame-resistant as plenum-rated cables (CL2P), CL2R cables meet the NEC’s stringent riser-rating requirements, offering a balance of safety, durability, and electrical performance.
These cables are typically made with PVC or other flame-retardant thermoplastic materials that can self-extinguish and resist burning. Their construction allows them to perform reliably in demanding commercial and industrial environments where vertical cable runs are required, such as in large office buildings, healthcare facilities, manufacturing plants, and data centers. CL2R cables are commonly used in systems that transmit low-voltage power and signals for security, control, and communication systems.
The National Electrical Code (NEC) governs the use of CL2R cables under Article 725, which outlines safety and performance standards for power-limited circuits. These cables are also tested and certified by Underwriters Laboratories (UL) according to UL 1666, the standard test for flame propagation height in riser installations. Together, these organizations ensure that CL2R cables comply with national fire protection and electrical safety requirements.
The CL2R designation emerged as building codes evolved to address the risks of fire spreading through multi-story structures. In the late 20th century, the NEC introduced the “riser” classification to distinguish cables that met vertical flame test criteria from those used in plenum or general-purpose spaces. This differentiation helped improve building fire safety while allowing for efficient electrical and data communication between floors.
These applications rely on CL2R cables for safe and consistent low-voltage signal transmission while maintaining compliance with fire-resistance standards.