When it comes to installing cables in commercial or residential buildings, knowing the differences between plenum and riser cables is crucial to proper installation and safety precautions. This is because the right cables in the right areas provide fire safety and clean air quality to those inside of the building.

This article discusses the differences between plenum-rated and riser cables to help you learn when to use the correct cables.

What Are Plenum Cables?

A plenum is part of a building that is used to circulate air, usually for heating, air-conditioning, and ventilation. It is kept in a separate part of the building, typically between a structural and drop-down ceiling, though it can also be found in the space underneath a raised floor.

As can be expected, structures such as plenum areas can affect the quality of the air within a building. From hot heaters in the winter to cold A/C systems in the summer, having high-quality, durable cables is necessary for keeping the people within the building safe from fire risks and air pollutants. That’s where plenum cables come in.

Plenum cables are designed to withstand high temperatures. Their high heat resistance is superior to that of other cables, making them appropriate for environmentally-sensitive areas within a building.

Types of Plenum Cables

Common types of plenum cables that you might see include the following:

• CMP: This cable stands for Communications Multipurpose Plenum. It is versatile and can be installed in plenum areas or other areas as well.
• Cat6P: This cable is CMP-rated and is therefore a multipurposed cable.
• CATVP: The Cable TV Plenum is a broadband cable.
• CL2P: The Class 2 Plenum cable is usually installed into walls.
• CL3P: The Class 3 Plenum cable is similar to the CL2P, but it has higher voltage ratings.

What Are Riser Cables?

Unlike plenum areas of a building, a riser area is vertical. This vertical space goes between the floors of a building. Like plenum cables, cables that are put in risers need to be fire-proof to prevent the building from catching on fire. Risers, however, don’t emit as high of heat as plenum spaces, meaning the code for fire requirements is more lenient for riser cables.

Types of Riser Cables

Riser cables also come in a wide selection of choices. Here are the most common riser cables and their general functions:

• CMR: Communications Multipurpose Riser are multipurpose riser cables that can be used for many riser areas.
• Cat6 CMR: The Cat6 multipurpose cable is a commercial-grade riser cable and can prevent the spread of fires between vertical floors of a building.
• CATVR: Cable TV riser is designed for broadband cables.
• CL2R: The Class 2 riser cable is installed into the wall. Like the CL2P, the CL2R has a lower voltage rating than the CL3R.

• CL3R: Class 3 riser cable is similar to the CL2R, only with a higher voltage.

When to Use Plenum-Rated and Riser Cables

Since plenum and riser areas function very differently from one another, the type of cables used in the installation process may differ. The best way to know when to use plenum or riser cables is by looking at their differences.

Let’s take a look at their different characteristics to help you determine when to use the appropriate cables.

Price Differences Between Plenum and Riser Cables

Firstly, there is a noticeable price difference between the various types of plenum and riser cables. Though a few of the aforementioned cable options within the two types of cables can vary, this is far more pronounced when looking at risers versus plenum cables.

Plenum cables cost more than riser cables because they need to meet higher requirements and are more durable and better suited to higher temperatures. In many cases, plenum cables can even replace the riser cables in a building. Generally, your building’s code will dictate what cables are permitted on your premises.

Location, Functionality, and Pathways of Plenum and Riser Cables

Knowing when to use plenum and riser cables is key to getting the most out of the building’s cable system. Depending on the location, functionality, and pathways of the particular area in question, your building will either have set codes or instructions for installing plenum or riser cables.

Nevertheless, here are general features of both cable types that might determine when to use them in buildings.

When to Use Plenum Cables

Plenum cables, as stated previously, occupy plenum areas in commercial and residential buildings. These areas are designated to air circulation.

From heating to air conditioning, plenum cables (especially ones like Cat6 plenum cables) help create circulation pathways in the air ducts and are engineered specifically to prevent the spread of fires.

Plenum cables also help reduce the amount of harmful air, toxic chemicals, and smoke that might arise in the case of a fire. This is because all plenum cables have outer jackets that are uniquely treated to insulate the wires inside.

As such, plenum cables must meet rigorous standards as per the National Fire Protection Association (NFPA) and National Electric Code (NEC).

When to Use Riser Cables

Riser cables, on the other hand, occupy riser areas in non-plenum spaces. As such, they are generally used in elevator shafts, electrical conduits, and other spaces that run vertically between multiple floors.

Most buildings have riser spaces to install the cables. These spaces can be shared with other electrical equipment or kept in a designated closet area.

Riser cables are frequently used for communications cabling, connecting the service entrance point of a distribution system to all levels of the building. Though riser cables are less hazardous than plenum cables if in contact with fire, riser cables must meet NFPA fire safety regulations for all cables. All riser cables have self-extinguishing mechanisms in the case of fire.

Professional Cable Installation

With all of the information available about plenum and riser cables, it can still be challenging to decipher which codes apply to which areas of a building. That’s why it’s important to have a professional cable contractor inspect the installation site and install the appropriate cables to your building.  Give Data Cabling Florida a call so we can help you with your structured cabling projects.