Plenum Rated Cables vs Riser Cables vs Non-Plenum
As AV integrators, we know plenum cables are costly, and when bidding on new projects we tend to avoid quoting them when possible (to the great satisfaction of most end-users). However, while cable choices are abundant, you may find yourself in a situation where you don’t have a choice at all.
What is Plenum?
Plenum is a term used by contractors, engineers, and HVAC technicians and is defined as a space used for air/ heating ventilation and circulation – think air ducts in a drop ceiling. A plenum-rated cable (CMP) actually refers to the coating around the cable, not the cable itself (coaxial, Cat5e/Cat6 ethernet, HDMI, etc.). A plenum rated cable’s jacket is highly fire-resistant, made from low smoke material, and less toxic. The reason plenum spaces require CMPs is because these spaces can accelerate fire propagation. Plenum rated cables limit flame growth, release less harmful smoke, and self-extinguish making it much safer in the event of an emergency.
So, when do you need to use plenum rated cables?
When it’s required by the National Fire Protection Association (NFPA):
All 50 states adhere to the National Electric Code, which details several cable ratings, including CMP cables, CMR cables, and CL/ CM cables. If you don’t meet the NEC requirements, you likely won’t be giving occupancy and could face heavy fines. Quick tip – most commercial codes require either plenum or riser-rated cables.
When you can’t use riser cables:
Riser cables are generally more cost-effective than plenum and meet the fire resistance standards of the NFPA. However, riser cables can only be used in non-plenum environments and do not replace plenum cables.
When it’s a plenum space:
We previously used drop ceilings as an example of plenum spaces, but this isn’t always the case! Sometimes drop ceilings are used as return air passageways; thus, plenum rated cable is not necessary. It’s always best to confirm plenum spaces with the contractor or building maintenance.
When insurance is costly:
Although CMP be as much as three times the cost of PVC, some commercial property owners may see significant savings on their insurance premiums by lowering liabilities with plenum cables. You’ll see this trend in buildings with high occupancy, like schools and hospitals, rather than warehouses or distribution centers.
If you don’t face any of these situations as a commercial integrator, it’s still best to explain all cable options to your end-user. Whether it’s in PVC or insurance premiums, they’ll appreciate the cost savings, making you look like a hero.