Where Do I Install Riser and Plenum Cable?
Posted on August 28 2019
This is a reasonably common question that we get asked often, as both cables look physically identical. However, it is important to adhere to the fire codes and use the proper cable for your installation. Here is a simple breakdown of where to run riser and plenum cable.
Plenum Cable (CMP)
Plenum cable is used for plenum areas. Yes, that sounds simple doesn't it, but what is a plenum area? Plenum is a space that facilitates air flow for air conditioning and heating systems by providing a pathway for the air to flow in and out of. The most common spaces are between drop ceilings or under a raised floor. Now why would you need plenum cable for these areas? Plenum cable has a more fire resistant jacket than other cables. The jacket burns at a slower rate and most importantly releases less hazardous smoke. With plenum areas circulating air throughout the building, it's important to reduce hazardous smoke should the cables catch on fire. The reason for the substantial cost difference is the material cost. Plenum cable is made of Fluorinated Ethylene Propylene (FEP) material, which is nearly double the cost of riser cable material Polyolefin (PO).
Riser Cable (CMR)
Also referred to as PVC. Riser cable is most commonly ran through walls and any other non plenum areas. Plenum cable can always replace riser cable, but riser cable cannot replace plenum cable in plenum areas.
How do I know if it's real plenum or riser cable?
There are many cables listed as plenum rated or riser rated, however it can nearly impossible to tell the difference to an inexperienced eye. A quick way to tell the two apart is to simply feel the outer jacket. Riser cable are usually more glossy and have a very smooth feel to the outer jacket and plenum jacket tend to be a bit more matte type of look and feel. You can dig deeper by stripping the overall jacket and you can see each wire. The color coding on each wire will usually be more faint on plenum cable, the reason being FEP material is transparent so the insulation on each pair will appear a bit more lighter. The insulation riser cable uses is PO (polyolefin), the color coding on each pair for this type of wire will be more bright and bold. This method is not the most precise, but you can usually distinguish the difference right away.
The most accurate way to tell if you're getting real plenum or riser cable is to simply ask your supplier for a test report. Every trusted supplier should have access to the flame test report for the cable they are offering. These test reports are supplied through a reputable testing lab such as ETL (Electrical Testing Lab) or UL (Underwriters Laboratories). These two are the largest and most trusted laboratories for testing the standards of electrical safety. In other words, if the cable is ETL Certified or UL Listed then it is safe to say they're true plenum or riser.
It is important to note that the price difference between both cables can be substantial, on average plenum is almost double the cost of riser cable. This is due to the material cost to produce each type of cable. For wholesale pricing on ETL certified and UL listed cable you can visit our homepage: One Stop Cables.