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What is Plenum Cable?

by Jeff Atkins on September 15, 2017
what is plenum cable

Category cables have all types of different terms and standards. Knowing what goes where and when to use the right cable is important for safety and electrical code compliance. On this blog post we will focus on one of those terms and that is Plenum cable. We will go over what is plenum cable, what are plenum spaces and whether you really do need plenum cable or not for your installation project.

What Is a Plenum?

The word plenum refers to a space, usually above a ceiling or below a floor, that can serve as a receiving chamber for air that has been heated or cooled to be distributed to inhabited areas. In simplified terms: it is the space above a building’s dropped ceiling or below a raised floor that gets used for heating, ventilation or air conditioning often known as HVAC. They are important areas for buildings in that they control the flow of air throughout.

What Does Plenum Have to Do with Cabling?

In addition to HVAC usage, plenum spaces are often used to house networking cables being run throughout a building. The cables used to run through these plenum spaces are referred to as Plenum Cable or abbreviated as CMP. The difference between plenum cable and other cables are the jacket material. True plenum cable uses flame retardant low smoke materials such as Teflon FEP, should there be a fire the cable would emit minimal amounts of harmful fumes compared to lower grade jackets. This material is created to self emit it's flame better than any other cable jacket rating. Why is this important? When running cable in areas with air flow the spread of flames increase because of that. This is where plenum cable come in to play. Plenum (CMP) are the only permitted networking cables that can be installed in areas with air flow (Plenum spaces). By installing plenum rated cable you help ensure that your building code is met along with safety standards.

area where plenum cable can go

Why Do I Need Plenum Cable?

It all boils down to safety. This one aspect can not be talked about enough when diving into networking cable and products.  Plenum rated cable goes through extensive flame tests to adhere to UL and National fire Protection Association standards. Plenum cable is less hazardous and emits the lowest amount of fumes should there be a fire. Legally, it is required by National electrical Code NEC if you’re installing any cabling in plenum areas. It’s necessary since plenum cables are installed through air circulation spaces which has very few fire barriers, they require coating that will not add to the spreading of flames.

The additional thing to mention about plenum rated cable is their insulation material, FEP. Insulation is the material that covers your ethernet cables copper wires.

FEP material has been shown to perform better in areas with higher temperatures. In plenum areas you can expect the temperature to raise from time to time. This can be from outside conditions or equipment and working conditions. So aside from it's safety benefit you get the plus of operating at higher temperatures more efficiently than other insulation materials such as PVC or ECTFCE.

Refer to this image for additional information on plenum and the other cable jacket ratings.

chart showing what plenum cable is

Things to Know When Shopping for Plenum Cable

We have touched on this before in this article but one of the first things that should be prioritized when shopping for plenum cable is certification. There are many different certification companies in the market today. Two of the most popular ones are UL and ETL. These two companies test your cables to ensure that proper safety measures are met. So double check that your cables are UL or ETL verified. Note here that UL certification is the highest certification standard for ethernet cables.

Make sure that your cable have 100% pure copper wires. This ensures that your plenum cables have the proper materials to perform to their desired spec. Plenum cables can not have copper clad aluminum wires. Anything other than pure copper cables will result in diminishing quality and can fail to meet your ethernet cable spec.

Final Thoughts

We hope this article on what is plenum cable was helpful. When you're ready head on over to our plenum cable collection. This collection has many different categories and types to fit any installation scenario. We carry shielded, unshielded, Cat5e to Cat8 cables and each come in many different options such as pull boxes and on reels.


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