What does it mean if a cable is riser rated cable or plenum rated cable? Riser and plenum refer to the material of the cable and how well suited they are in case of a building fire. When determining between whether riser or plenum cable would be best for a particular installation, one has to know what they are and what purposes they serve.
What is Riser Cable?
Riser cables are made from plastics and materials that are flame-retardant. They meet fire-resistant standards set by UL1666. They are used in installations that require going in between multiple floors of buildings. Riser cables are larger in diameter and color codes are more vivid than in plenum cables. All types of cables can be riser cables: network, audio, thermostat, and more.
What is Plenum Cable?
Plenum cables are made from a flame-retardant and low-smoke polyvinyl chloride (PVC) or FEP (fluorinated ethylene polymer). They have to meet stricter fire safety standards because plenum cables are installed in plenum areas in buildings. The National Fire Protection Association (NFPA) standards NFPA 262 and NFPA 90A set the standards for plastics and other materials used in plenum cables. Because plenum cables are installed in an area that poses as a high-risk fire danger, they are also put through intense fire safety tests. Plenum cable jackets are thinner and the color codes are not as opaque as those on riser cable are. Just like riser cables, plenum cables consist of a variety of different cables: network, audio, thermostat, and more.
Plenum vs Riser vs In-Wall Cable Ratings and Usage
| Cable Ratings | Cable Usage |
|---|---|
| CMP, CL3P, CL2P, FPLP, CATVP | All In-Wall, Plenum, and Riser applications. |
| CMR, CL3R, CL2R, FPLR, CATVR | All In-Wall and Riser applications, not permitted in Plenum applications. |
| CM, CMG, CL3, CL2, FPL, CATV | In-Wall rated, permitted in 1-2 family residential Riser applications, or in Riser with raceway or fireproof shaft, not permitted in Plenum applications. |
Where to use Riser Cable and Plenum Cable?
Riser rated cable is a cable that is suited to go in non-plenum spaces and between multiple floors of buildings. Usually, riser cables are installed in between floors, and in walls of buildings. They can also be installed in areas that do not pose danger in case of a fire.
Plenum rated cable is a cable that is suited to go in the plenum spaces of buildings, such as ceilings and enclosures that are also used by the building for air distribution systems to transport air. Plenum spaces are the areas in between buildings where air circulates and supplies the Heating, Ventilation, and Air Conditioning (HVAC) systems. Plenum areas can be in drop ceilings or raised floors of buildings. A building’s communication, data, and other network cables are usually placed in this space.
In case of a fire, plenum cables are slower to burn. It also will prevent the fire from growing bigger and causing more damage and danger. This will allow time for people within buildings to leave the building safely.
The Cost of Riser and Plenum Cables
Plenum cables cost more than riser cables. Prices for plenum cable can be 50%-70% higher than riser cable. As plenum cables have to meet a stricter fire safety standard than riser cables, the materials used in plenum cables to meet these standards are usually more expensive than the material used in riser cables.
Can Riser be Used In Place of Plenum? 
Riser cables CANNOT be used in place of plenum cable. It is best to ALWAYS use plenum cable in installations and spaces that require plenum cable. After all, the design and manufacture of plenum cables are to ensure the safety of a building and a building’s inhabitants.
Should Riser or Plenum Cable be Used?
The type of installation determines which cable, riser or plenum, is used. If the installation only goes between floors in non-plenum areas, riser cable is sufficient. If budget is an issue, riser cable is usually cheaper than plenum rated cable. However, for use in plenum areas, always best use plenum rated cable. Plenum rated can be used in place of riser rated cable. Riser rated cable is NEVER to be used in installations where plenum rated cable are required. That way in case of fire, damage is limited. For Network Ethernet connectors, RJ45 plugs, etc. they are the same for riser and plenum cables. In the end, the choice of cable should be one that best fits the installation’s parameters. For more information, please check our Technical Guides of NEC and Flame Test Reference.
Do You Need Plenum-Rated Cable if it’s in Conduit?
If you’re using a plenum-rated conduit, you don’t need to use a plenum-rated cable. This is true even if the conduit is in a plenum space. The most common types of plenum conduit are inner duct (often used for fiber runs) and metal. PVC pipes are generally not plenum-rated.
However, installing conduits is expensive, and purchasing plenum-rated cable is often easier and cheaper.
Plenum Cables for Smart Buildings
Smart buildings require an intelligent infrastructure that can support an integrated network of building systems. The intelligent cabling infrastructure becomes the foundation of a smart building. Because of the diversity of applications and the requirements and locations, the Plenum Cables are recommended for smart buildings.
Have More Questions?
Have more questions that we haven’t covered here? Please feel free to reach out to us!
Syston Cable Technology has a variety of riser-rated and plenum-rated cables perfect to suit any installation. Check out our website, YouTube, or contact us for more information.
** Written by Syston Cable Team **
Resources:
Wikipedia
Blue Wave Communications