Wire and Cable Technology for LANs - LAN Wiring - page 103

TABLE 5.3
Common National Electrical Code ® ( NEC ® ) Cable-Use Codes for Metallic Communications and
Control Cable

NEC ®
Article

Code Meaning Allowable Substitutions*

725 CL3P Class 3 Plenum MPP CMP FPLP

CL3R Class 3 Riser CL3P MPR CMR FPLR

CL3 Class 3 CL3P CL3R MP MPG CM CMG FPL PLTC

CL3X Class 3, limited use CL3P CL3R CL3 MP MPG CM CMG FPL PLTC CMX

CL2P Class 2 Plenum Cl3P

CL2R Class 2 Riser CL3P CL2P CL3R

CL2 Class 2 CL3P CL3R CL2P CL2R CL3 MP MPG CM CMG

FPL PLTC

CL2X Class 2, limited use CL3P CL3R CL2P CL2R CL2 CL3 CL3X MP MPG

CM CMG FPL PLTC CMX

800 MPP Multipurpose Plenum None

MPR Multipurpose Riser MPP

MP, MPG Multipurpose MPP MPR

CMP Communications MPP

Plenum
CMR Communications Riser MPP CMP MPR
CM, CMG Communications MPP CMR MPG MP
CMX Communications CMG CM
limited uset 14
*In general, a cable with a more strict usage code may be substituted in an application that allows a less strict usage
code. For example, a cable rated to the stricter Class 2, Plenum (CL2P) code may be substituted in Class 2, Riser
(CL2R) application. Likewise, CMP, MPP, and FPLP, which may be substituted for CL3P, will substitute for any code
that allows CL3P to be substituted. The chart does not list all possible substitutions, only those to the next level.
Source: 1996 NEC ® .

The confusing labeling of NEC ® and UL ® specifications led to a revision of the
NEC ® , in 1987, that instituted a system of alphanumeric designators for permissible
cable-use ratings. The common cable-use codes are shown in Table 5.3. Cables may
be specified that meet or exceed the requirements for a specified use. You may find
cable that has dual markings, if the cable is certified for use in each classification.

The FEP Controversy

The impact of computer networking on the plastic materials industry has been felt
very directly by users of plenum-rated cable. Plenum cable uses insulation and some-
times jacketing made with fluorocarbon plastics for their smoke- and flame-retar-
dant properties. Fluorinated ethylene-propylene (FEP) is often the material most
used for insulating the individual conductors because of its superior dielectric prop-
erties at the very high frequencies of modern LAN cable.