Q: Can you interchange riser and plenum cables?
A: No. They are different. Plenum and Riser refer to places in a building in which the cables can be used. This distinction is a requirement of national electrical code in the U.S. and other countries that may have similar electrical codes. In Canada, riser is referred to as FT4 and plenum is referred to a FT6. National electrical code in the U.S. requires that cables that are installed in a riser, which is a vertical shaft/chase or pathway in a building, must pass certain flammability requirements. Those requirements are established in UL test 1666. A plenum space in a building is one in which the air in that space is used by the HVAC air handling system as part of the air return. Those cables must past more restrictive requirements than riser rated cables. This UL test is referred to as UL910. The reason for the more restrictive plenum rating is that if the cables in a plenum space are involved in a fire, they must exhibit certain characteristics to minimize the danger created by the fire. Plenum rated cables require different materials than riser rated cables. National electrical code has a hierarchy of what cables can be used where. Plenum rated cables are at the top. They can be used about anywhere. Both cables must be clearly marked on their jackets to ensure that riser rated cables are not used in a plenum spaces. A plenum cable, as referenced above, can be used in a riser space since it is designed for a higher level of fire resistance.