For safety concern, many people would like to buy flame retardant cables, of which plenum cable and riser cable are top two flame retardant classes people may prefer. And of all the Ethernet cable categories, Cat6 cables are mostly adopted to apply in the two classes. Then, what is Cat6 plenum cable? What is Cat6 riser cable? Why is the former one more expensive than the latter one?
Before knowing what the Cat6 plenum cables and Cat6 riser cables are, you have to be familiar with flame retardant Ethernet cable jacket coatings in the first place.
At present, there are two widely used flame retardant cable types, namely PVC Underwriters Laboratories cable (UL cable, US fire protection standards) and Low Smoke Zero Halogen cable (LSZH cable, European national fire protection standards). Since Cat6 plenum cables and Cat6 riser cables belong to the UL cable type, here, we will focus on the PVC UL cable. It includes a series of cables which are divided into five classes according to their safety standards and using environments. The five classes are CMP cable, CMR cable, CM cable, CMG cable and CMX cable. Then, what are their relations with plenum cables and riser cables? Just read on to find out why.
Actually, Cat6 plenum cable is Cat6 CMP cable. The CMP cable (Communications Multipurpose Cable, Plenum) is the most demanding cable in the UL fire protection standard, the safety standard is UL910. This cable is designed to restrict flame propagation to no more than five feet, and to limit the amount of smoke emitted during a fire. Therefore, the Cat6 plenum cable is suitable for installation into air plenum spaces. Normally, a Cat6 plenum cable jacket is made up from either a low-smoke polyvinyl chloride (PVC) or a fluorinated ethylene polymer (FEP).
The Cat6 plenum cables are designed to provide pathways for return airflows of buildings, facilitating air circulation for heating and air conditioning systems. These Cat6 cables are typically used in the air return pressure boosting system used in ventilation ducts or air handling equipment (above a suspended ceiling or under a raised floor, for example). Since the fire and smoke can travel and spread quickly through these plenum spaces full of fresh oxygen, which may cause damage to the furniture and threaten people’s lives, the Cat6 plenum cables are essential to prevent the fire from spreading out.
Cat6 riser cable, also regarded as Cat6 CMR cable (Communications Multipurpose Cable, Riser), is the commercial grade cable in the UL standard, applicable to the UL1666 safety standard. It is constructed to prevent fires from spreading floor to floor in vertical installations. Thus, it is generally used for floor vertical wiring. Unlike a Cat6 plenum cable, a Cat6 riser cable usually has a jacket covering made up from the relatively inexpensive polyvinyl chloride (PVC)
From the introduction above, you may know that a riser cable is installed between floors in non-plenum areas. It is the primary conduit of a building’s distribution system, carrying voice, data and video into the different spaces and levels of a building from the service entrance point.
Actually, through all the illustrations above, there is no doubt that a Cat6 plenum cable (CMP cable) is more expensive than a Cat6 riser cable (CMR cable) given the difference in cable jacket material and safety standard.
For a Cat6 plenum cable, it uses low-smoke PVC or FEP, which has superior chemical resistance and electrical properties. It can support an operating temperature from -25 to 125 degrees Celsius. And it is resistant against all kinds of chemicals. And for a Cat6 riser cable, it uses relatively inexpensive PVC and such PVC material may release thick smoke and dangerous gases like hydrogen chloride in a fire. The operating temperature of a Cat6 riser cable is from 0 to 70 degrees Celsius. That’s one reason why a Cat6 plenum cable is more expensive than a riser one.
Cat6 plenum cables and Cat6 riser cables also differ in safety standard. The former one meets the standard of UL910, which is the strictest standard, making plenum cables the most demanding. While, the latter one meets the standard of UL1666, not as strict as the former one. Since the requirements for riser cables are lower, plenum cables are usually used as an alternative of riser cables, but not vice versa. Here is an example of typical applications of the two Cat6 cable types.
Last but not least, you can get clearer understanding of the Cat6 plenum cable and Cat6 riser cable from the chart listed below.
To sum up, both Cat6 plenum cables and Cat6 riser cables are flame retardant Cat6 Ethernet cables, the former one meets higher requirements in cable jacket material and safety standard, resulting in a more expensive price. You can choose between the two cable types according to your actual needs.