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Cable Jacket Ratings, Uses, and Substitutions

When installing cabling in walls and ceilings it is important to use cables that meet the local code requirements. Local codes are typically based on the National Electric Code (NEC) published by the National Fire Protection Association. The NEC contains a large amount of information and covers a wide variety of electrical installations. The majority of the NEC document is devoted to electrical power installations, but it also covers the installation of other cabling that is integrated into a building's structure in any way.

The requirements in the NEC are designed to prevent hazards to human health and safety from wiring including electrical shock, the tendency to start or perpetuate a fire, and the production of toxic fumes when exposed to fire. The NEC provides classification standards for cables with jackets that are suitable for reducing these risks, i.e. CL2, or Class 2. Almost all of these cable ratings permit in–wall installation per the NEC. In–wall cabling is typically sufficient for residential installations. The NEC also covers specialized cabling that is designed to be installed within a plenum or a riser in a structure.

A plenum, under Article 100 of the NEC, is a compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system. Plenum spaces are primarily seen in commercial environments. An example of the most common types of plenum spaces would be a dropped ceiling or raised floor. Most homes do not have significant plenum spaces, so plenum cabling is rarely a concern for residential installations. To receive a plenum rating the cabling is required to use material in the construction of the jacket and dielectric which do not easily give off toxic fumes if burned. The reason for this is that if there is a fire in one part of the building then toxic fumes could be fed to the remainder of the building through the ventilation system. The term riser applies to a space that is not specifically defined in the NEC, but is a requirement for cabling that will penetrate from one floor of a building to another.

Common Jacket Ratings

Rating Usage
CMP All in-wall, plenum and riser applications.
CMR, CL3R, CL2R All in-wall and riser applications; not permitted in plenums.
CM, CMG, CL2 In-wall rated; permitted in 1-2 family residential riser applications, or in riser with raceway/fireproof shaft; not permitted in plenums.
Rating Description May be substituted for: Other ratings that will satisfy the requirement:
CMP Communications, Plenum CL3P, CL2P, CATVP, CMR, CL2R, CL3R, CATVR, CM, CMG, CL2, CL3, CATV, CMX, CL2X, CL3X, CATVX None
CATVP Cable TV, Plenum CATVR, CATV, CATVX CMP
CL3P Class 3, Plenum CL2P, CL3R, CL2R, CL3, CL2, CL2X, CL3X CMP
CL2P Class 2, Plenum CL2R, CL2, CL2X CMP, CL3P
CMR Communications, Riser CL3R, CL2R, CATVR, CM, CMG, CL3, CL2, CATV, CMX, CL2X, CL3X, CATVX CMP
CATVR Cable TV, Riser CATV, CATVX CMP, CATVP, CMR
CL3R Class 3, Riser CL2R, CL3, CL2, CL3X, CL2X CMP, CL3P, CMR
CL2R Class 2, Riser CL2, CL2X CMP, CL3P, CMR, CL3R
CM or CMG Communications CL3, CL2, CATV, CL3X, CL2X, CATVX CMP, CMR
CATV Cable TV CATVX CMP, CATVP, CMR, CATVR, CM, CMG
CL3 Class 3 CL2, CL3X, CL2X CMP, CL3P, CMR, CL3R, CM, CMG
CL2 Class 2 CL2X CMP, CL3P, CL2P, CMR, CL3R, CL2R, CM, CMG, CL3
CMX Communications, Residential CL3X, CL2X, CATV CMP, CMR, CM, CMG
CATVX Cable TV, Residential None CMP, CATVP, CMR, CATVR, CM, CMG, CATV, CMX
CL3X Class 3, Residential CL2X CMP, CL3P, CMR, CL3R, CM, CMG, CL3, CMX
CL2X Class 2, Residential None CMP, CL3P, CL2P, CMR, CL3R, CL2R, CM, CMG, CL3, CL2, CMX, CL3X

This white paper is for informational purposes only and is subject to change without notice. C2G makes no guarantees, either expressed or implied, concerning the accuracy, completeness or reliability of the information found in this document.