In this blog, ETU-LINK will introduce the fire rating standards of copper cables. The flame retardant grades of copper cables are divided into four grades: CMX, CM, CMR, and CMP. The minimum is CMX.

The insulation layer of the CMP cable is made of FEP material, and the outer sheath is made of PVC. FEP has strong fire resistance and can endure temperatures as high as 800°C or more before it disintegrates with burning smoke. Therefore, FEP is very suitable for making cables that transmit high-speed data. CMP has the highest flame retardant grade among UL fireproof materials. Its flame retardant performance is better than that of LSZH, and the concentration of smoke when burned is very low, so CMP cables have a high level of data security.

CMR is a trunk-level communication copper cable, which is the second-ranked cable. When a bundle of trunk-level cables is forced to blow by a fan, the flame will extinguish itself within 5M (the maximum flame spread is 3.6 meters). CMR cable The jacket is generally made of some type of PVC, which when burned emits chlorine gas, which depletes the air of oxygen and extinguishes the flame. CMR grade cables are widely used in trunk applications where the ventilation system is physically separate from the wiring system.

CM is commercial-grade copper cable, CMG is general-purpose copper cable, commercial-grade and general-grade cables do not have smoke concentration specifications, and the bundled cables will self-extinguish within 5M when burning (the maximum flame spread is 2.4 meters), commercial-grade cables Cables are generally used for horizontal cables, and horizontal cables are generally placed in wire troughs or pipes, so generally speaking, the fire rating will be significantly improved in the case of casing, and customers will not worry about using commercial-grade cables for horizontal cables cause some hidden dangers. Generally, it is only applied to the horizontal wiring of the same floor, not to the vertical wiring of the floor.

CMX is a residential communication cable, this grade also has no smoke or toxicity specifications and is only used in home or small office systems where a single cable is run. Such cables should not be bundled and must be sleeved.

Finally, in a brief summary, CMX is the cable with the lowest fire resistance and is usually used as an auxiliary cable; CM/CMG is used for horizontal wiring and can be used on the same floor; CMR is used for vertical wiring and can be used across floors; CMP is used in forced ventilation environments and has the highest fire resistance.