When do i need plenum cable

Some residential buildings are never inspected. Depending on your jurisdiction, you may need to simply show that your cable is plenum-rated. In some stricter jurisdictions, you may need to show that the cable is UL listed as well. The following cables meet plenum-rating specifications, but are not UL listed:.

UL-listed cable should generally be marked with the UL trademark marking and approval number, which you can use to look up the cable online for free.

Non-plenum cables can be used anywhere except plenum space and air ducts. In both commercial and residential buildings, non-plenum cable can be used to run cables through walls and across open ceilings. You must use CMR riser-rated cable when running cable between floors through risers or vertical shafts. Some buildings with HVAC systems have return air ducts which transport air back outdoors. If there are no leakages and the space above a drop ceiling is not circulating air, you may use non-plenum cable.

Of course, this is only true as long as the cable is not running inside the air ducts themselves. Non-circulating plenum airspace may become active due to disconnected ductwork. But, before you go ahead, check with your insurance provider and local area building code. Some insurance providers and building codes require plenum cable even for non-plenum spaces depending on factors like building height, purpose and occupancy.

This is true even if the conduit is in a plenum space. The most common types of plenum conduit are innerduct often used for fiber runs and metal. PVC pipes are generally not plenum-rated. However, installing conduit is expensive, and purchasing plenum-rated cable is often easier and cheaper.

Have more questions that we haven't covered here? Please leave a comment or reach out to us! Plenum is a separate space provided for air circulation for heating, ventilation, and air-conditioning also referred to as HVAC , which is the space between the structural ceiling and a drop-down ceiling.

And it may also be under a raised floor. Plenum cable is also called CMP Communications Multipurpose Cable, Plenum for short, which is the cable that is laid in the plenum spaces of buildings.

The cable is designed to restrict flame propagation and limit the amount of smoke. Compared with the traditional PVC cable, plenum cable produces less smoke. Thus, plenum cable is suitable for installation into air plenum spaces, especially in the locations like schools and hospitals for safety concerns.

Non-plenum cable usually serves to run through non-air circulating areas. Non-plenum includes riser rated cable, and other rated cables like CM cable, etc. The fire rating of riser cable is not as strict as the plenum cable since plenum cable uses less hazardous and lower smoke materials. Thus, plenum cable can replace riser cable, but not the other way around. And the price of riser cable is less than plenum cable.

Usually, the cable can be deployed to run between floors through risers or vertical shafts. However, in many cases we are called in to provide a solution in an existing building. So how do we know which to choose? If you look in the office and see an air vent return grate that is pulling the air from the office into the ceiling, and it is using ducting in the ceiling to do this, then you can use non-plenum cable barring any specific code requirements for that facility.

Here's a non-plenum example:. If the return air vent is just emptying into the open space above the ceiling with no ducting, then the open space is considered to be a plenum area and will require plenum cable. A plenum area like this reacts to a fire differently.